The kernel.h is a set of something which is not related to each other and often used in non-crossed compilation units, especially when drivers need only one or two macro definitions from it.
Here is the split of container_of(). The goals are the following: - untwist the dependency hell a bit - drop kernel.h inclusion where it's only used for container_of() - speed up C preprocessing.
People, like Greg KH and Miguel Ojeda, were asking about the latter. Read below the methodology and test setup with outcome numbers.
The methodology =============== The question here is how to measure in the more or less clean way the C preprocessing time when building a project like Linux kernel. To answer it, let's look around and see what tools do we have that may help. Aha, here is ccache tool that seems quite plausible to be used. Its core idea is to preprocess C file, count hash (MD4) and compare to ones that are in the cache. If found, return the object file, avoiding compilation stage.
Taking into account the property of the ccache, configure and use it in the below steps:
1. Configure kernel with allyesconfig
2. Make it with `make` to be sure that the cache is filled with the latest data. I.o.w. warm up the cache.
3. Run `make -s` (silent mode to reduce the influence of the unrelated things, like console output) 10 times and measure 'real' time spent.
4. Repeat 1-3 for each patch or patch set to get data sets before and after.
When we get the raw data, calculating median will show us the number. Comparing them before and after we will see the difference.
The setup ========= I have used the Intel x86_64 server platform (see partial output of `lscpu` below):
$ lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 46 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 88 On-line CPU(s) list: 0-87 Vendor ID: GenuineIntel Model name: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz CPU family: 6 Model: 79 Thread(s) per core: 2 Core(s) per socket: 22 Socket(s): 2 Stepping: 1 CPU max MHz: 3600.0000 CPU min MHz: 1200.0000 ... Caches (sum of all): L1d: 1.4 MiB (44 instances) L1i: 1.4 MiB (44 instances) L2: 11 MiB (44 instances) L3: 110 MiB (2 instances) NUMA: NUMA node(s): 2 NUMA node0 CPU(s): 0-21,44-65 NUMA node1 CPU(s): 22-43,66-87 Vulnerabilities: Itlb multihit: KVM: Mitigation: Split huge pages L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable Mds: Mitigation; Clear CPU buffers; SMT vulnerable Meltdown: Mitigation; PTI Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Spectre v2: Mitigation; Full generic retpoline, IBPB conditional, IBRS_FW, STIBP conditional, RSB filling Tsx async abort: Mitigation; Clear CPU buffers; SMT vulnerable
With the following GCC:
$ gcc --version gcc (Debian 10.3.0-11) 10.3.0
The commands I have run during the measurement were:
rm -rf $O make O=$O allyesconfig time make O=$O -s -j64 # this step has been measured
The raw data and median ======================= Before patch 2 (yes, I have measured the only patch 2 effect) in the series (the data is sorted by time):
real 2m8.794s real 2m11.183s real 2m11.235s real 2m11.639s real 2m11.960s real 2m12.014s real 2m12.609s real 2m13.177s real 2m13.462s real 2m19.132s
After patch 2 has been applied:
real 2m8.536s real 2m8.776s real 2m9.071s real 2m9.459s real 2m9.531s real 2m9.610s real 2m10.356s real 2m10.430s real 2m11.117s real 2m11.885s
Median values are: 131.987s before 129.571s after
We see the steady speedup as of 1.83%.
Andy Shevchenko (4): kernel.h: Drop unneeded <linux/kernel.h> inclusion from other headers kernel.h: Split out container_of() and typeof_member() macros lib/rhashtable: Replace kernel.h with the necessary inclusions kunit: Replace kernel.h with the necessary inclusions
include/kunit/test.h | 14 ++++++++++++-- include/linux/container_of.h | 37 ++++++++++++++++++++++++++++++++++++ include/linux/kernel.h | 31 +----------------------------- include/linux/kobject.h | 1 + include/linux/list.h | 6 ++++-- include/linux/llist.h | 4 +++- include/linux/plist.h | 5 ++++- include/linux/rwsem.h | 1 - include/linux/spinlock.h | 1 - include/media/media-entity.h | 3 ++- lib/radix-tree.c | 6 +++++- lib/rhashtable.c | 7 ++++++- 12 files changed, 75 insertions(+), 41 deletions(-) create mode 100644 include/linux/container_of.h
There is no evidence we need kernel.h inclusion in certain headers. Drop unneeded <linux/kernel.h> inclusion from other headers.
Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com --- include/linux/rwsem.h | 1 - include/linux/spinlock.h | 1 - 2 files changed, 2 deletions(-)
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 352c6127cb90..f9348769e558 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -11,7 +11,6 @@ #include <linux/linkage.h>
#include <linux/types.h> -#include <linux/kernel.h> #include <linux/list.h> #include <linux/spinlock.h> #include <linux/atomic.h> diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 76a855b3ecde..c04e99edfe92 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -57,7 +57,6 @@ #include <linux/compiler.h> #include <linux/irqflags.h> #include <linux/thread_info.h> -#include <linux/kernel.h> #include <linux/stringify.h> #include <linux/bottom_half.h> #include <linux/lockdep.h>
kernel.h is being used as a dump for all kinds of stuff for a long time. Here is the attempt cleaning it up by splitting out container_of() and typeof_member() macros.
At the same time convert users in the header and other folders to use it. Though for time being include new header back to kernel.h to avoid twisted indirected includes for existing users.
Note, there are _a lot_ of headers and modules that include kernel.h solely for one of these macros and this allows to unburden compiler for the twisted inclusion paths and to make new code cleaner in the future.
Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com --- include/kunit/test.h | 2 ++ include/linux/container_of.h | 37 ++++++++++++++++++++++++++++++++++++ include/linux/kernel.h | 31 +----------------------------- include/linux/kobject.h | 1 + include/linux/list.h | 6 ++++-- include/linux/llist.h | 4 +++- include/linux/plist.h | 5 ++++- include/media/media-entity.h | 3 ++- lib/radix-tree.c | 6 +++++- lib/rhashtable.c | 1 + 10 files changed, 60 insertions(+), 36 deletions(-) create mode 100644 include/linux/container_of.h
diff --git a/include/kunit/test.h b/include/kunit/test.h index 24b40e5c160b..4d498f496790 100644 --- a/include/kunit/test.h +++ b/include/kunit/test.h @@ -11,6 +11,8 @@
#include <kunit/assert.h> #include <kunit/try-catch.h> + +#include <linux/container_of.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/slab.h> diff --git a/include/linux/container_of.h b/include/linux/container_of.h new file mode 100644 index 000000000000..f6ee1be0e784 --- /dev/null +++ b/include/linux/container_of.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_CONTAINER_OF_H +#define _LINUX_CONTAINER_OF_H + +#define typeof_member(T, m) typeof(((T*)0)->m) + +/** + * container_of - cast a member of a structure out to the containing structure + * @ptr: the pointer to the member. + * @type: the type of the container struct this is embedded in. + * @member: the name of the member within the struct. + * + */ +#define container_of(ptr, type, member) ({ \ + void *__mptr = (void *)(ptr); \ + BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \ + !__same_type(*(ptr), void), \ + "pointer type mismatch in container_of()"); \ + ((type *)(__mptr - offsetof(type, member))); }) + +/** + * container_of_safe - cast a member of a structure out to the containing structure + * @ptr: the pointer to the member. + * @type: the type of the container struct this is embedded in. + * @member: the name of the member within the struct. + * + * If IS_ERR_OR_NULL(ptr), ptr is returned unchanged. + */ +#define container_of_safe(ptr, type, member) ({ \ + void *__mptr = (void *)(ptr); \ + BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \ + !__same_type(*(ptr), void), \ + "pointer type mismatch in container_of()"); \ + IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) : \ + ((type *)(__mptr - offsetof(type, member))); }) + +#endif /* _LINUX_CONTAINER_OF_H */ diff --git a/include/linux/kernel.h b/include/linux/kernel.h index d416fe3165cb..ad9fdcce9dcf 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -9,6 +9,7 @@ #include <linux/stddef.h> #include <linux/types.h> #include <linux/compiler.h> +#include <linux/container_of.h> #include <linux/bitops.h> #include <linux/kstrtox.h> #include <linux/log2.h> @@ -482,36 +483,6 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { } #define __CONCAT(a, b) a ## b #define CONCATENATE(a, b) __CONCAT(a, b)
-/** - * container_of - cast a member of a structure out to the containing structure - * @ptr: the pointer to the member. - * @type: the type of the container struct this is embedded in. - * @member: the name of the member within the struct. - * - */ -#define container_of(ptr, type, member) ({ \ - void *__mptr = (void *)(ptr); \ - BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \ - !__same_type(*(ptr), void), \ - "pointer type mismatch in container_of()"); \ - ((type *)(__mptr - offsetof(type, member))); }) - -/** - * container_of_safe - cast a member of a structure out to the containing structure - * @ptr: the pointer to the member. - * @type: the type of the container struct this is embedded in. - * @member: the name of the member within the struct. - * - * If IS_ERR_OR_NULL(ptr), ptr is returned unchanged. - */ -#define container_of_safe(ptr, type, member) ({ \ - void *__mptr = (void *)(ptr); \ - BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \ - !__same_type(*(ptr), void), \ - "pointer type mismatch in container_of()"); \ - IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) : \ - ((type *)(__mptr - offsetof(type, member))); }) - /* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */ #ifdef CONFIG_FTRACE_MCOUNT_RECORD # define REBUILD_DUE_TO_FTRACE_MCOUNT_RECORD diff --git a/include/linux/kobject.h b/include/linux/kobject.h index efd56f990a46..bf8371e58b17 100644 --- a/include/linux/kobject.h +++ b/include/linux/kobject.h @@ -15,6 +15,7 @@ #ifndef _KOBJECT_H_ #define _KOBJECT_H_
+#include <linux/container_of.h> #include <linux/types.h> #include <linux/list.h> #include <linux/sysfs.h> diff --git a/include/linux/list.h b/include/linux/list.h index f2af4b4aa4e9..5dc679b373da 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -2,11 +2,13 @@ #ifndef _LINUX_LIST_H #define _LINUX_LIST_H
+#include <linux/container_of.h> +#include <linux/const.h> #include <linux/types.h> #include <linux/stddef.h> #include <linux/poison.h> -#include <linux/const.h> -#include <linux/kernel.h> + +#include <asm/barrier.h>
/* * Circular doubly linked list implementation. diff --git a/include/linux/llist.h b/include/linux/llist.h index 24f207b0190b..85bda2d02d65 100644 --- a/include/linux/llist.h +++ b/include/linux/llist.h @@ -49,7 +49,9 @@ */
#include <linux/atomic.h> -#include <linux/kernel.h> +#include <linux/container_of.h> +#include <linux/stddef.h> +#include <linux/types.h>
struct llist_head { struct llist_node *first; diff --git a/include/linux/plist.h b/include/linux/plist.h index 66bab1bca35c..0f352c1d3c80 100644 --- a/include/linux/plist.h +++ b/include/linux/plist.h @@ -73,8 +73,11 @@ #ifndef _LINUX_PLIST_H_ #define _LINUX_PLIST_H_
-#include <linux/kernel.h> +#include <linux/container_of.h> #include <linux/list.h> +#include <linux/types.h> + +#include <asm/bug.h>
struct plist_head { struct list_head node_list; diff --git a/include/media/media-entity.h b/include/media/media-entity.h index 09737b47881f..fea489f03d57 100644 --- a/include/media/media-entity.h +++ b/include/media/media-entity.h @@ -13,10 +13,11 @@
#include <linux/bitmap.h> #include <linux/bug.h> +#include <linux/container_of.h> #include <linux/fwnode.h> -#include <linux/kernel.h> #include <linux/list.h> #include <linux/media.h> +#include <linux/types.h>
/* Enums used internally at the media controller to represent graphs */
diff --git a/lib/radix-tree.c b/lib/radix-tree.c index b3afafe46fff..a0f346a095df 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -12,19 +12,21 @@ #include <linux/bitmap.h> #include <linux/bitops.h> #include <linux/bug.h> +#include <linux/container_of.h> #include <linux/cpu.h> #include <linux/errno.h> #include <linux/export.h> #include <linux/idr.h> #include <linux/init.h> -#include <linux/kernel.h> #include <linux/kmemleak.h> +#include <linux/math.h> #include <linux/percpu.h> #include <linux/preempt.h> /* in_interrupt() */ #include <linux/radix-tree.h> #include <linux/rcupdate.h> #include <linux/slab.h> #include <linux/string.h> +#include <linux/types.h> #include <linux/xarray.h>
/* @@ -285,6 +287,8 @@ radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent, return ret; }
+extern void radix_tree_node_rcu_free(struct rcu_head *head); + void radix_tree_node_rcu_free(struct rcu_head *head) { struct radix_tree_node *node = diff --git a/lib/rhashtable.c b/lib/rhashtable.c index e12bbfb240b8..a422c7dd9126 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -12,6 +12,7 @@ */
#include <linux/atomic.h> +#include <linux/container_of.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/log2.h>
On Thu, Oct 07, 2021 at 12:51:27PM +0300, Andy Shevchenko wrote:
kernel.h is being used as a dump for all kinds of stuff for a long time. Here is the attempt cleaning it up by splitting out container_of() and typeof_member() macros.
At the same time convert users in the header and other folders to use it. Though for time being include new header back to kernel.h to avoid twisted indirected includes for existing users.
Note, there are _a lot_ of headers and modules that include kernel.h solely for one of these macros and this allows to unburden compiler for the twisted inclusion paths and to make new code cleaner in the future.
Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com
include/kunit/test.h | 2 ++ include/linux/container_of.h | 37 ++++++++++++++++++++++++++++++++++++ include/linux/kernel.h | 31 +----------------------------- include/linux/kobject.h | 1 + include/linux/list.h | 6 ++++-- include/linux/llist.h | 4 +++- include/linux/plist.h | 5 ++++- include/media/media-entity.h | 3 ++- lib/radix-tree.c | 6 +++++- lib/rhashtable.c | 1 + 10 files changed, 60 insertions(+), 36 deletions(-) create mode 100644 include/linux/container_of.h
diff --git a/include/kunit/test.h b/include/kunit/test.h index 24b40e5c160b..4d498f496790 100644 --- a/include/kunit/test.h +++ b/include/kunit/test.h @@ -11,6 +11,8 @@ #include <kunit/assert.h> #include <kunit/try-catch.h>
+#include <linux/container_of.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/slab.h> diff --git a/include/linux/container_of.h b/include/linux/container_of.h new file mode 100644 index 000000000000..f6ee1be0e784 --- /dev/null +++ b/include/linux/container_of.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_CONTAINER_OF_H +#define _LINUX_CONTAINER_OF_H
+#define typeof_member(T, m) typeof(((T*)0)->m)
+/**
- container_of - cast a member of a structure out to the containing structure
- @ptr: the pointer to the member.
- @type: the type of the container struct this is embedded in.
- @member: the name of the member within the struct.
- */
+#define container_of(ptr, type, member) ({ \
- void *__mptr = (void *)(ptr); \
- BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
!__same_type(*(ptr), void), \"pointer type mismatch in container_of()"); \- ((type *)(__mptr - offsetof(type, member))); })
+/**
- container_of_safe - cast a member of a structure out to the containing structure
- @ptr: the pointer to the member.
- @type: the type of the container struct this is embedded in.
- @member: the name of the member within the struct.
- If IS_ERR_OR_NULL(ptr), ptr is returned unchanged.
- */
+#define container_of_safe(ptr, type, member) ({ \
- void *__mptr = (void *)(ptr); \
- BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
!__same_type(*(ptr), void), \"pointer type mismatch in container_of()"); \- IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) : \
((type *)(__mptr - offsetof(type, member))); })+#endif /* _LINUX_CONTAINER_OF_H */ diff --git a/include/linux/kernel.h b/include/linux/kernel.h index d416fe3165cb..ad9fdcce9dcf 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -9,6 +9,7 @@ #include <linux/stddef.h> #include <linux/types.h> #include <linux/compiler.h> +#include <linux/container_of.h> #include <linux/bitops.h> #include <linux/kstrtox.h> #include <linux/log2.h> @@ -482,36 +483,6 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { } #define __CONCAT(a, b) a ## b #define CONCATENATE(a, b) __CONCAT(a, b) -/**
- container_of - cast a member of a structure out to the containing structure
- @ptr: the pointer to the member.
- @type: the type of the container struct this is embedded in.
- @member: the name of the member within the struct.
- */
-#define container_of(ptr, type, member) ({ \
- void *__mptr = (void *)(ptr); \
- BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
!__same_type(*(ptr), void), \"pointer type mismatch in container_of()"); \- ((type *)(__mptr - offsetof(type, member))); })
-/**
- container_of_safe - cast a member of a structure out to the containing structure
- @ptr: the pointer to the member.
- @type: the type of the container struct this is embedded in.
- @member: the name of the member within the struct.
- If IS_ERR_OR_NULL(ptr), ptr is returned unchanged.
- */
-#define container_of_safe(ptr, type, member) ({ \
- void *__mptr = (void *)(ptr); \
- BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
!__same_type(*(ptr), void), \"pointer type mismatch in container_of()"); \- IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) : \
((type *)(__mptr - offsetof(type, member))); })/* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */ #ifdef CONFIG_FTRACE_MCOUNT_RECORD # define REBUILD_DUE_TO_FTRACE_MCOUNT_RECORD diff --git a/include/linux/kobject.h b/include/linux/kobject.h index efd56f990a46..bf8371e58b17 100644 --- a/include/linux/kobject.h +++ b/include/linux/kobject.h @@ -15,6 +15,7 @@ #ifndef _KOBJECT_H_ #define _KOBJECT_H_ +#include <linux/container_of.h> #include <linux/types.h> #include <linux/list.h> #include <linux/sysfs.h> diff --git a/include/linux/list.h b/include/linux/list.h index f2af4b4aa4e9..5dc679b373da 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -2,11 +2,13 @@ #ifndef _LINUX_LIST_H #define _LINUX_LIST_H +#include <linux/container_of.h> +#include <linux/const.h> #include <linux/types.h> #include <linux/stddef.h> #include <linux/poison.h> -#include <linux/const.h> -#include <linux/kernel.h>
+#include <asm/barrier.h> /*
- Circular doubly linked list implementation.
This change looks odd.
You already have kernel.h including container_of.h, so why not have a series that does: - create container_of.h and have kernel.h include it - multiple patches that remove kernel.h and use container_of.h instead only. - multiple patches that remove kernel.h and use container_of.h and other .h files (like list.h seems to need here.) - remove container_of.h from kernel.h
Mushing them all together here makes this really hard to understand why this change is needed here.
thanks,
greg k-h
On Thu, Oct 07, 2021 at 12:51:27PM +0300, Andy Shevchenko wrote:
--- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -12,19 +12,21 @@ #include <linux/bitmap.h> #include <linux/bitops.h> #include <linux/bug.h> +#include <linux/container_of.h> #include <linux/cpu.h> #include <linux/errno.h> #include <linux/export.h> #include <linux/idr.h> #include <linux/init.h> -#include <linux/kernel.h> #include <linux/kmemleak.h> +#include <linux/math.h> #include <linux/percpu.h> #include <linux/preempt.h> /* in_interrupt() */ #include <linux/radix-tree.h> #include <linux/rcupdate.h> #include <linux/slab.h> #include <linux/string.h> +#include <linux/types.h> #include <linux/xarray.h> /* @@ -285,6 +287,8 @@ radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent, return ret; } +extern void radix_tree_node_rcu_free(struct rcu_head *head);
.c files should not need an extern, this belongs in a .h file somewhere, or something really went wrong here...
thanks,
greg k-h
When kernel.h is used in the headers it adds a lot into dependency hell, especially when there are circular dependencies are involved.
Replace kernel.h inclusion with the list of what is really being used.
Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com --- lib/rhashtable.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/lib/rhashtable.c b/lib/rhashtable.c index a422c7dd9126..01502cf77564 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -12,9 +12,13 @@ */
#include <linux/atomic.h> +#include <linux/bit_spinlock.h> #include <linux/container_of.h> -#include <linux/kernel.h> +#include <linux/err.h> +#include <linux/export.h> #include <linux/init.h> +#include <linux/jhash.h> +#include <linux/lockdep.h> #include <linux/log2.h> #include <linux/sched.h> #include <linux/rculist.h>
On Thu, Oct 07, 2021 at 12:51:28PM +0300, Andy Shevchenko wrote:
When kernel.h is used in the headers it adds a lot into dependency hell, especially when there are circular dependencies are involved.
Replace kernel.h inclusion with the list of what is really being used.
Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com
lib/rhashtable.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/lib/rhashtable.c b/lib/rhashtable.c index a422c7dd9126..01502cf77564 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -12,9 +12,13 @@ */ #include <linux/atomic.h> +#include <linux/bit_spinlock.h> #include <linux/container_of.h> -#include <linux/kernel.h> +#include <linux/err.h> +#include <linux/export.h> #include <linux/init.h> +#include <linux/jhash.h> +#include <linux/lockdep.h> #include <linux/log2.h> #include <linux/sched.h> #include <linux/rculist.h>
Nack. I can see the benefits of splitting things out of kernel.h but there is no reason to add crap to end users like rhashtable.c.
Thanks,
On Thu, Oct 07, 2021 at 07:23:28PM +0800, Herbert Xu wrote:
On Thu, Oct 07, 2021 at 12:51:28PM +0300, Andy Shevchenko wrote:
When kernel.h is used in the headers it adds a lot into dependency hell, especially when there are circular dependencies are involved.
Replace kernel.h inclusion with the list of what is really being used.
Nack. I can see the benefits of splitting things out of kernel.h but there is no reason to add crap to end users like rhashtable.c.
Crap is in the kernel.h. Could you elaborate how making a proper list of the inclusions is a crap?
On Thu, Oct 07, 2021 at 02:44:41PM +0300, Andy Shevchenko wrote:
Crap is in the kernel.h. Could you elaborate how making a proper list of the inclusions is a crap?
Unless you're planning on not including all those header files from kernel.h, then adding them all to an end node like rhashtable.c is just a waste of time.
You should be targetting other header files and not c files.
Thanks,
When kernel.h is used in the headers it adds a lot into dependency hell, especially when there are circular dependencies are involved.
Replace kernel.h inclusion with the list of what is really being used.
Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com --- include/kunit/test.h | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/include/kunit/test.h b/include/kunit/test.h index 4d498f496790..d88d9f7ead0a 100644 --- a/include/kunit/test.h +++ b/include/kunit/test.h @@ -12,12 +12,20 @@ #include <kunit/assert.h> #include <kunit/try-catch.h>
+#include <linux/compiler_attributes.h> #include <linux/container_of.h> -#include <linux/kernel.h> +#include <linux/err.h> +#include <linux/init.h> +#include <linux/kconfig.h> +#include <linux/kref.h> +#include <linux/list.h> #include <linux/module.h> #include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/string.h> #include <linux/types.h> -#include <linux/kref.h> + +#include <asm/rwonce.h>
struct kunit_resource;
On Thu, Oct 07, 2021 at 12:51:25PM +0300, Andy Shevchenko wrote:
The kernel.h is a set of something which is not related to each other and often used in non-crossed compilation units, especially when drivers need only one or two macro definitions from it.
Here is the split of container_of(). The goals are the following:
- untwist the dependency hell a bit
- drop kernel.h inclusion where it's only used for container_of()
- speed up C preprocessing.
People, like Greg KH and Miguel Ojeda, were asking about the latter. Read below the methodology and test setup with outcome numbers.
The methodology
The question here is how to measure in the more or less clean way the C preprocessing time when building a project like Linux kernel. To answer it, let's look around and see what tools do we have that may help. Aha, here is ccache tool that seems quite plausible to be used. Its core idea is to preprocess C file, count hash (MD4) and compare to ones that are in the cache. If found, return the object file, avoiding compilation stage.
Taking into account the property of the ccache, configure and use it in the below steps:
Configure kernel with allyesconfig
Make it with `make` to be sure that the cache is filled with the latest data. I.o.w. warm up the cache.
Run `make -s` (silent mode to reduce the influence of the unrelated things, like console output) 10 times and measure 'real' time spent.
Repeat 1-3 for each patch or patch set to get data sets before and after.
When we get the raw data, calculating median will show us the number. Comparing them before and after we will see the difference.
The setup
I have used the Intel x86_64 server platform (see partial output of `lscpu` below):
$ lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 46 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 88 On-line CPU(s) list: 0-87 Vendor ID: GenuineIntel Model name: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz CPU family: 6 Model: 79 Thread(s) per core: 2 Core(s) per socket: 22 Socket(s): 2 Stepping: 1 CPU max MHz: 3600.0000 CPU min MHz: 1200.0000 ... Caches (sum of all): L1d: 1.4 MiB (44 instances) L1i: 1.4 MiB (44 instances) L2: 11 MiB (44 instances) L3: 110 MiB (2 instances) NUMA: NUMA node(s): 2 NUMA node0 CPU(s): 0-21,44-65 NUMA node1 CPU(s): 22-43,66-87 Vulnerabilities: Itlb multihit: KVM: Mitigation: Split huge pages L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable Mds: Mitigation; Clear CPU buffers; SMT vulnerable Meltdown: Mitigation; PTI Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Spectre v2: Mitigation; Full generic retpoline, IBPB conditional, IBRS_FW, STIBP conditional, RSB filling Tsx async abort: Mitigation; Clear CPU buffers; SMT vulnerable
With the following GCC:
$ gcc --version gcc (Debian 10.3.0-11) 10.3.0
The commands I have run during the measurement were:
rm -rf $O make O=$O allyesconfig time make O=$O -s -j64 # this step has been measured
The raw data and median
Before patch 2 (yes, I have measured the only patch 2 effect) in the series (the data is sorted by time):
real 2m8.794s real 2m11.183s real 2m11.235s real 2m11.639s real 2m11.960s real 2m12.014s real 2m12.609s real 2m13.177s real 2m13.462s real 2m19.132s
After patch 2 has been applied:
real 2m8.536s real 2m8.776s real 2m9.071s real 2m9.459s real 2m9.531s real 2m9.610s real 2m10.356s real 2m10.430s real 2m11.117s real 2m11.885s
Median values are: 131.987s before 129.571s after
We see the steady speedup as of 1.83%.
You do know about kcbench: https://gitlab.com/knurd42/kcbench.git
Try running that to make it such that we know how it was tested :)
thanks,
greg k-h
Andy Shevchenko (4): kernel.h: Drop unneeded <linux/kernel.h> inclusion from other headers kernel.h: Split out container_of() and typeof_member() macros lib/rhashtable: Replace kernel.h with the necessary inclusions kunit: Replace kernel.h with the necessary inclusions
include/kunit/test.h | 14 ++++++++++++-- include/linux/container_of.h | 37 ++++++++++++++++++++++++++++++++++++ include/linux/kernel.h | 31 +----------------------------- include/linux/kobject.h | 1 + include/linux/list.h | 6 ++++-- include/linux/llist.h | 4 +++- include/linux/plist.h | 5 ++++- include/linux/rwsem.h | 1 - include/linux/spinlock.h | 1 - include/media/media-entity.h | 3 ++- lib/radix-tree.c | 6 +++++- lib/rhashtable.c | 7 ++++++- 12 files changed, 75 insertions(+), 41 deletions(-) create mode 100644 include/linux/container_of.h
-- 2.33.0
On Thu, Oct 7, 2021 at 1:34 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Thu, Oct 07, 2021 at 12:51:25PM +0300, Andy Shevchenko wrote:
The kernel.h is a set of something which is not related to each other and often used in non-crossed compilation units, especially when drivers need only one or two macro definitions from it.
Here is the split of container_of(). The goals are the following:
- untwist the dependency hell a bit
- drop kernel.h inclusion where it's only used for container_of()
- speed up C preprocessing.
People, like Greg KH and Miguel Ojeda, were asking about the latter. Read below the methodology and test setup with outcome numbers.
The methodology
The question here is how to measure in the more or less clean way the C preprocessing time when building a project like Linux kernel. To answer it, let's look around and see what tools do we have that may help. Aha, here is ccache tool that seems quite plausible to be used. Its core idea is to preprocess C file, count hash (MD4) and compare to ones that are in the cache. If found, return the object file, avoiding compilation stage.
Taking into account the property of the ccache, configure and use it in the below steps:
Configure kernel with allyesconfig
Make it with `make` to be sure that the cache is filled with the latest data. I.o.w. warm up the cache.
Run `make -s` (silent mode to reduce the influence of the unrelated things, like console output) 10 times and measure 'real' time spent.
Repeat 1-3 for each patch or patch set to get data sets before and after.
When we get the raw data, calculating median will show us the number. Comparing them before and after we will see the difference.
The setup
I have used the Intel x86_64 server platform (see partial output of `lscpu` below):
$ lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 46 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 88 On-line CPU(s) list: 0-87 Vendor ID: GenuineIntel Model name: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz CPU family: 6 Model: 79 Thread(s) per core: 2 Core(s) per socket: 22 Socket(s): 2 Stepping: 1 CPU max MHz: 3600.0000 CPU min MHz: 1200.0000 ... Caches (sum of all): L1d: 1.4 MiB (44 instances) L1i: 1.4 MiB (44 instances) L2: 11 MiB (44 instances) L3: 110 MiB (2 instances) NUMA: NUMA node(s): 2 NUMA node0 CPU(s): 0-21,44-65 NUMA node1 CPU(s): 22-43,66-87 Vulnerabilities: Itlb multihit: KVM: Mitigation: Split huge pages L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable Mds: Mitigation; Clear CPU buffers; SMT vulnerable Meltdown: Mitigation; PTI Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Spectre v2: Mitigation; Full generic retpoline, IBPB conditional, IBRS_FW, STIBP conditional, RSB filling Tsx async abort: Mitigation; Clear CPU buffers; SMT vulnerable
With the following GCC:
$ gcc --version gcc (Debian 10.3.0-11) 10.3.0
The commands I have run during the measurement were:
rm -rf $O make O=$O allyesconfig time make O=$O -s -j64 # this step has been measuredThe raw data and median
Before patch 2 (yes, I have measured the only patch 2 effect) in the series (the data is sorted by time):
real 2m8.794s real 2m11.183s real 2m11.235s real 2m11.639s real 2m11.960s real 2m12.014s real 2m12.609s real 2m13.177s real 2m13.462s real 2m19.132s
After patch 2 has been applied:
real 2m8.536s real 2m8.776s real 2m9.071s real 2m9.459s real 2m9.531s real 2m9.610s real 2m10.356s real 2m10.430s real 2m11.117s real 2m11.885s
Median values are: 131.987s before 129.571s after
We see the steady speedup as of 1.83%.
You do know about kcbench: https://gitlab.com/knurd42/kcbench.git
Try running that to make it such that we know how it was tested :)
I'll try it.
Meanwhile, Thorsten, can you have a look at my approach and tell if it makes sense?
On Thu, Oct 07, 2021 at 02:51:15PM +0300, Andy Shevchenko wrote:
On Thu, Oct 7, 2021 at 1:34 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Thu, Oct 07, 2021 at 12:51:25PM +0300, Andy Shevchenko wrote:
The kernel.h is a set of something which is not related to each other and often used in non-crossed compilation units, especially when drivers need only one or two macro definitions from it.
Here is the split of container_of(). The goals are the following:
- untwist the dependency hell a bit
- drop kernel.h inclusion where it's only used for container_of()
- speed up C preprocessing.
People, like Greg KH and Miguel Ojeda, were asking about the latter. Read below the methodology and test setup with outcome numbers.
The methodology
The question here is how to measure in the more or less clean way the C preprocessing time when building a project like Linux kernel. To answer it, let's look around and see what tools do we have that may help. Aha, here is ccache tool that seems quite plausible to be used. Its core idea is to preprocess C file, count hash (MD4) and compare to ones that are in the cache. If found, return the object file, avoiding compilation stage.
Taking into account the property of the ccache, configure and use it in the below steps:
Configure kernel with allyesconfig
Make it with `make` to be sure that the cache is filled with the latest data. I.o.w. warm up the cache.
Run `make -s` (silent mode to reduce the influence of the unrelated things, like console output) 10 times and measure 'real' time spent.
Repeat 1-3 for each patch or patch set to get data sets before and after.
When we get the raw data, calculating median will show us the number. Comparing them before and after we will see the difference.
The setup
I have used the Intel x86_64 server platform (see partial output of `lscpu` below):
$ lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 46 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 88 On-line CPU(s) list: 0-87 Vendor ID: GenuineIntel Model name: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz CPU family: 6 Model: 79 Thread(s) per core: 2 Core(s) per socket: 22 Socket(s): 2 Stepping: 1 CPU max MHz: 3600.0000 CPU min MHz: 1200.0000 ... Caches (sum of all): L1d: 1.4 MiB (44 instances) L1i: 1.4 MiB (44 instances) L2: 11 MiB (44 instances) L3: 110 MiB (2 instances) NUMA: NUMA node(s): 2 NUMA node0 CPU(s): 0-21,44-65 NUMA node1 CPU(s): 22-43,66-87 Vulnerabilities: Itlb multihit: KVM: Mitigation: Split huge pages L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable Mds: Mitigation; Clear CPU buffers; SMT vulnerable Meltdown: Mitigation; PTI Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Spectre v2: Mitigation; Full generic retpoline, IBPB conditional, IBRS_FW, STIBP conditional, RSB filling Tsx async abort: Mitigation; Clear CPU buffers; SMT vulnerable
With the following GCC:
$ gcc --version gcc (Debian 10.3.0-11) 10.3.0
The commands I have run during the measurement were:
rm -rf $O make O=$O allyesconfig time make O=$O -s -j64 # this step has been measuredThe raw data and median
Before patch 2 (yes, I have measured the only patch 2 effect) in the series (the data is sorted by time):
real 2m8.794s real 2m11.183s real 2m11.235s real 2m11.639s real 2m11.960s real 2m12.014s real 2m12.609s real 2m13.177s real 2m13.462s real 2m19.132s
After patch 2 has been applied:
real 2m8.536s real 2m8.776s real 2m9.071s real 2m9.459s real 2m9.531s real 2m9.610s real 2m10.356s real 2m10.430s real 2m11.117s real 2m11.885s
Median values are: 131.987s before 129.571s after
We see the steady speedup as of 1.83%.
You do know about kcbench: https://gitlab.com/knurd42/kcbench.git
Try running that to make it such that we know how it was tested :)
I'll try it.
Meanwhile, Thorsten, can you have a look at my approach and tell if it makes sense?
No, do not use ccache when trying to benchmark the speed of kernel builds, that tests the speed of your disk subsystem...
thanks,
greg k-h
On Thu, Oct 07, 2021 at 03:59:08PM +0200, Greg Kroah-Hartman wrote:
On Thu, Oct 07, 2021 at 02:51:15PM +0300, Andy Shevchenko wrote:
On Thu, Oct 7, 2021 at 1:34 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
...
Meanwhile, Thorsten, can you have a look at my approach and tell if it makes sense?
No, do not use ccache when trying to benchmark the speed of kernel builds, that tests the speed of your disk subsystem...
First rule of the measurement is to be sure WHAT we are measuring. And I'm pretty much explained WHAT and HOW. On the other hand, the kcbench can't answer to the question about C preprocessing speed without help of ccache or something similar.
Measuring complete build is exactly not what we want because of O(compilation) vs. o(C preprocessing) meaning that any fluctuation in the former makes silly to measure anything from the latter.
You see, my theory is proved by practical experiment:
$ kcbench -i 3 -j 64 -o $O -s $PWD --no-download -m Processor: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz [88 CPUs] Cpufreq; Memory: powersave [intel_pstate]; 128823 MiB Linux running: 5.6.0-2-amd64 [x86_64] Compiler: gcc (Debian 10.3.0-11) 10.3.0 Linux compiled: 5.15.0-rc4 Config; Environment: allmodconfig; CCACHE_DISABLE="1" Build command: make vmlinux modules Filling caches: This might take a while... Done Run 1 (-j 64): 464.07 seconds / 7.76 kernels/hour [P:6001%] Run 2 (-j 64): 464.64 seconds / 7.75 kernels/hour [P:6000%] Run 3 (-j 64): 486.41 seconds / 7.40 kernels/hour [P:5727%]
$ kcbench -i 3 -j 64 -o $O -s $PWD --no-download -m Processor: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz [88 CPUs] Cpufreq; Memory: powersave [intel_pstate]; 128823 MiB Linux running: 5.6.0-2-amd64 [x86_64] Compiler: gcc (Debian 10.3.0-11) 10.3.0 Linux compiled: 5.15.0-rc4 Config; Environment: allmodconfig; CCACHE_DISABLE="1" Build command: make vmlinux modules Filling caches: This might take a while... Done Run 1 (-j 64): 462.32 seconds / 7.79 kernels/hour [P:6009%] Run 2 (-j 64): 462.33 seconds / 7.79 kernels/hour [P:6006%] Run 3 (-j 64): 465.45 seconds / 7.73 kernels/hour [P:5999%]
In [41]: numpy.median(y1) Out[41]: 464.64
In [42]: numpy.median(y2) Out[42]: 462.33
Speedup: +0.5%
On Thu, Oct 07, 2021 at 05:47:31PM +0300, Andy Shevchenko wrote:
On Thu, Oct 07, 2021 at 03:59:08PM +0200, Greg Kroah-Hartman wrote:
On Thu, Oct 07, 2021 at 02:51:15PM +0300, Andy Shevchenko wrote:
On Thu, Oct 7, 2021 at 1:34 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
...
Meanwhile, Thorsten, can you have a look at my approach and tell if it makes sense?
No, do not use ccache when trying to benchmark the speed of kernel builds, that tests the speed of your disk subsystem...
First rule of the measurement is to be sure WHAT we are measuring. And I'm pretty much explained WHAT and HOW. On the other hand, the kcbench can't answer to the question about C preprocessing speed without help of ccache or something similar.
Measuring complete build is exactly not what we want because of O(compilation) vs. o(C preprocessing) meaning that any fluctuation in the former makes silly to measure anything from the latter.
You see, my theory is proved by practical experiment:
$ kcbench -i 3 -j 64 -o $O -s $PWD --no-download -m Processor: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz [88 CPUs] Cpufreq; Memory: powersave [intel_pstate]; 128823 MiB Linux running: 5.6.0-2-amd64 [x86_64] Compiler: gcc (Debian 10.3.0-11) 10.3.0 Linux compiled: 5.15.0-rc4 Config; Environment: allmodconfig; CCACHE_DISABLE="1" Build command: make vmlinux modules Filling caches: This might take a while... Done Run 1 (-j 64): 464.07 seconds / 7.76 kernels/hour [P:6001%] Run 2 (-j 64): 464.64 seconds / 7.75 kernels/hour [P:6000%] Run 3 (-j 64): 486.41 seconds / 7.40 kernels/hour [P:5727%]
$ kcbench -i 3 -j 64 -o $O -s $PWD --no-download -m Processor: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz [88 CPUs] Cpufreq; Memory: powersave [intel_pstate]; 128823 MiB Linux running: 5.6.0-2-amd64 [x86_64] Compiler: gcc (Debian 10.3.0-11) 10.3.0 Linux compiled: 5.15.0-rc4 Config; Environment: allmodconfig; CCACHE_DISABLE="1" Build command: make vmlinux modules Filling caches: This might take a while... Done Run 1 (-j 64): 462.32 seconds / 7.79 kernels/hour [P:6009%] Run 2 (-j 64): 462.33 seconds / 7.79 kernels/hour [P:6006%] Run 3 (-j 64): 465.45 seconds / 7.73 kernels/hour [P:5999%]
In [41]: numpy.median(y1) Out[41]: 464.64
In [42]: numpy.median(y2) Out[42]: 462.33
Speedup: +0.5%
Good, you measured what actually matters here, the real compilation of the code, not just the pre-processing of it.
thanks,
greg k-h
(sorry, sending it a second time with a different mail client, as vger rejected my earlier mail with the "Content-Policy reject msg: Wrong MIME labeling on 8-bit character texts." – and as of now I'm unable to figure out what's wrong :-/ )
On Thu, 7 Oct 2021 14:51:15 +0300 Andy Shevchenko andy.shevchenko@gmail.com wrote:
On Thu, Oct 7, 2021 at 1:34 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Thu, Oct 07, 2021 at 12:51:25PM +0300, Andy Shevchenko wrote:
The kernel.h is a set of something which is not related to each other and often used in non-crossed compilation units, especially when drivers need only one or two macro definitions from it.
Here is the split of container_of(). The goals are the following:
- untwist the dependency hell a bit
- drop kernel.h inclusion where it's only used for container_of()
- speed up C preprocessing.
People, like Greg KH and Miguel Ojeda, were asking about the latter. Read below the methodology and test setup with outcome numbers.
The methodology
The question here is how to measure in the more or less clean way the C preprocessing time when building a project like Linux kernel. To answer it, let's look around and see what tools do we have that may help. Aha, here is ccache tool that seems quite plausible to be used. Its core idea is to preprocess C file, count hash (MD4) and compare to ones that are in the cache. If found, return the object file, avoiding compilation stage.
Taking into account the property of the ccache, configure and use it in the below steps:
Configure kernel with allyesconfig
Make it with `make` to be sure that the cache is filled with the latest data. I.o.w. warm up the cache.
Run `make -s` (silent mode to reduce the influence of the unrelated things, like console output) 10 times and measure 'real' time spent.
Repeat 1-3 for each patch or patch set to get data sets before and after.
When we get the raw data, calculating median will show us the number. Comparing them before and after we will see the difference.
The setup
I have used the Intel x86_64 server platform (see partial output of `lscpu` below):
$ lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 46 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 88 On-line CPU(s) list: 0-87 Vendor ID: GenuineIntel Model name: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz CPU family: 6 Model: 79 Thread(s) per core: 2 Core(s) per socket: 22 Socket(s): 2 Stepping: 1 CPU max MHz: 3600.0000 CPU min MHz: 1200.0000 ... Caches (sum of all): L1d: 1.4 MiB (44 instances) L1i: 1.4 MiB (44 instances) L2: 11 MiB (44 instances) L3: 110 MiB (2 instances) NUMA: NUMA node(s): 2 NUMA node0 CPU(s): 0-21,44-65 NUMA node1 CPU(s): 22-43,66-87 Vulnerabilities: Itlb multihit: KVM: Mitigation: Split huge pages L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable Mds: Mitigation; Clear CPU buffers; SMT vulnerable Meltdown: Mitigation; PTI Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Spectre v2: Mitigation; Full generic retpoline, IBPB conditional, IBRS_FW, STIBP conditional, RSB filling Tsx async abort: Mitigation; Clear CPU buffers; SMT vulnerable
With the following GCC:
$ gcc --version gcc (Debian 10.3.0-11) 10.3.0
The commands I have run during the measurement were:
rm -rf $O make O=$O allyesconfig time make O=$O -s -j64 # this step has been measured
BTW, what kcbench does in the end is not that different, but it only builds the config once and that uses it for all further testing.
The raw data and median
Before patch 2 (yes, I have measured the only patch 2 effect) in the series (the data is sorted by time):
real 2m8.794s real 2m11.183s real 2m11.235s real 2m11.639s real 2m11.960s real 2m12.014s real 2m12.609s real 2m13.177s real 2m13.462s real 2m19.132s
After patch 2 has been applied:
real 2m8.536s real 2m8.776s real 2m9.071s real 2m9.459s real 2m9.531s real 2m9.610s real 2m10.356s real 2m10.430s real 2m11.117s real 2m11.885s
Median values are: 131.987s before 129.571s after
We see the steady speedup as of 1.83%.
You do know about kcbench: https://gitlab.com/knurd42/kcbench.git
Try running that to make it such that we know how it was tested :)
I'll try it.
Meanwhile, Thorsten, can you have a look at my approach and tell if it makes sense?
I'm not the right person to ask here, I don't know enough about the inner working of ccache and C preprocessing. Reminder: I'm not a real kernel/C developer, but more kind of a parasite that lives on the fringes of kernel development. ;-) Kcbench in fact originated as a benchmark magazine for the computer magazine I used to work for – where I also did quite a few benchmarks. But that knowledge might be helpful here:
The measurements before and after patch 2 was applied get slower over time. That is a hint that something is interfering. Is the disk filling up and making the fs do more work? Or is the machine getting to hot? It IMHO would be worth investigating and ruling out, as the differences you are looking out are likely quite small
Also: the last run of the first measurement cycle is off by quite a bit, so I wouldn't even include the result, as there like was something that disturbed the benchmark.
And I might be missing something, but why were you using "-j 64" on a machine with 44 cores/88 threads? I wonder if that might lead do interesting effects due to SMT (some core will run two threads, other only one). Using either "-j 44" or "-j 88" might be better. But I suggest you run kcbench once without specifying "-j", as that will check which setting is the fastest on this system – and then use that for all further tests.
HTH, Ciao, Thorsten
On Fri, Oct 08, 2021 at 11:37:58AM +0200, Thorsten Leemhuis wrote:
On Thu, 7 Oct 2021 14:51:15 +0300 Andy Shevchenko andy.shevchenko@gmail.com wrote:
On Thu, Oct 7, 2021 at 1:34 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Thu, Oct 07, 2021 at 12:51:25PM +0300, Andy Shevchenko wrote:
The kernel.h is a set of something which is not related to each other and often used in non-crossed compilation units, especially when drivers need only one or two macro definitions from it.
Here is the split of container_of(). The goals are the following:
- untwist the dependency hell a bit
- drop kernel.h inclusion where it's only used for container_of()
- speed up C preprocessing.
People, like Greg KH and Miguel Ojeda, were asking about the latter. Read below the methodology and test setup with outcome numbers.
The methodology
The question here is how to measure in the more or less clean way the C preprocessing time when building a project like Linux kernel. To answer it, let's look around and see what tools do we have that may help. Aha, here is ccache tool that seems quite plausible to be used. Its core idea is to preprocess C file, count hash (MD4) and compare to ones that are in the cache. If found, return the object file, avoiding compilation stage.
Taking into account the property of the ccache, configure and use it in the below steps:
Configure kernel with allyesconfig
Make it with `make` to be sure that the cache is filled with the latest data. I.o.w. warm up the cache.
Run `make -s` (silent mode to reduce the influence of the unrelated things, like console output) 10 times and measure 'real' time spent.
Repeat 1-3 for each patch or patch set to get data sets before and after.
When we get the raw data, calculating median will show us the number. Comparing them before and after we will see the difference.
The setup
I have used the Intel x86_64 server platform (see partial output of `lscpu` below):
$ lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 46 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 88 On-line CPU(s) list: 0-87 Vendor ID: GenuineIntel Model name: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz CPU family: 6 Model: 79 Thread(s) per core: 2 Core(s) per socket: 22 Socket(s): 2 Stepping: 1 CPU max MHz: 3600.0000 CPU min MHz: 1200.0000 ... Caches (sum of all): L1d: 1.4 MiB (44 instances) L1i: 1.4 MiB (44 instances) L2: 11 MiB (44 instances) L3: 110 MiB (2 instances) NUMA: NUMA node(s): 2 NUMA node0 CPU(s): 0-21,44-65 NUMA node1 CPU(s): 22-43,66-87 Vulnerabilities: Itlb multihit: KVM: Mitigation: Split huge pages L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable Mds: Mitigation; Clear CPU buffers; SMT vulnerable Meltdown: Mitigation; PTI Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Spectre v2: Mitigation; Full generic retpoline, IBPB conditional, IBRS_FW, STIBP conditional, RSB filling Tsx async abort: Mitigation; Clear CPU buffers; SMT vulnerable
With the following GCC:
$ gcc --version gcc (Debian 10.3.0-11) 10.3.0
The commands I have run during the measurement were:
rm -rf $O make O=$O allyesconfig time make O=$O -s -j64 # this step has been measuredBTW, what kcbench does in the end is not that different, but it only builds the config once and that uses it for all further testing.
Since I measure the third operation only this shouldn't affect recreation of the configuration file.
The raw data and median
Before patch 2 (yes, I have measured the only patch 2 effect) in the series (the data is sorted by time):
real 2m8.794s real 2m11.183s real 2m11.235s real 2m11.639s real 2m11.960s real 2m12.014s real 2m12.609s real 2m13.177s real 2m13.462s real 2m19.132s
After patch 2 has been applied:
real 2m8.536s real 2m8.776s real 2m9.071s real 2m9.459s real 2m9.531s real 2m9.610s real 2m10.356s real 2m10.430s real 2m11.117s real 2m11.885s
Median values are: 131.987s before 129.571s after
We see the steady speedup as of 1.83%.
You do know about kcbench: https://gitlab.com/knurd42/kcbench.git
Try running that to make it such that we know how it was tested :)
I'll try it.
Meanwhile, Thorsten, can you have a look at my approach and tell if it makes sense?
I'm not the right person to ask here, I don't know enough about the inner working of ccache and C preprocessing. Reminder: I'm not a real kernel/C developer, but more kind of a parasite that lives on the fringes of kernel development. ;-) Kcbench in fact originated as a benchmark magazine for the computer magazine I used to work for – where I also did quite a few benchmarks. But that knowledge might be helpful here:
The measurements before and after patch 2 was applied get slower over time. That is a hint that something is interfering. Is the disk filling up and making the fs do more work? Or is the machine getting to hot? It IMHO would be worth investigating and ruling out, as the differences you are looking out are likely quite small
I tried to explain why my methodology is closer to what we need to measure in the above and replies. TL;DR: mathematically the O() shadows o() and as we know the CPU and disk usage during compilation is a huge in comparison to the C preprocessing. I'm not sure what you are referring by "slower over time" since I explicitly said that I have _sorted_ the data. Nothing should be done here, I believe.
Also: the last run of the first measurement cycle is off by quite a bit, so I wouldn't even include the result, as there like was something that disturbed the benchmark.
I believe you missed the very same remark, i.e. that the data is sorted.
And I might be missing something, but why were you using "-j 64" on a machine with 44 cores/88 threads?
Because that machine has more processes being run. And I would like to minimize fluctuation of the CPU scheduling when some process requires a resource to perform little work.
I wonder if that might lead do interesting effects due to SMT (some core will run two threads, other only one). Using either "-j 44" or "-j 88" might be better.
How -j64 can be better? Nothing will guarantee that any of the core will be half-loaded. But -j88 is worse because any process that wakes up and requires for a resource may affect the measurements.
But I suggest you run kcbench once without specifying "-j", as that will check which setting is the fastest on this system – and then use that for all further tests.
Next time I will try this approach, thanks for your reply and insights!
linux-kselftest-mirror@lists.linaro.org
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Andy Shevchenko -
Andy Shevchenko -
Greg Kroah-Hartman -
Herbert Xu -
Thorsten Leemhuis