This series is a follow-up to [1], which adds mTHP support to khugepaged.
mTHP khugepaged support is a "loose" dependency for the sysfs/sysctl
configs to make sense. Without it global="defer" and mTHP="inherit" case
is "undefined" behavior.
We've seen cases were customers switching from RHEL7 to RHEL8 see a
significant increase in the memory footprint for the same workloads.
Through our investigations we found that a large contributing factor to
the increase in RSS was an increase in THP usage.
For workloads like MySQL, or when using allocators like jemalloc, it is
often recommended to set /transparent_hugepages/enabled=never. This is
in part due to performance degradations and increased memory waste.
This series introduces enabled=defer, this setting acts as a middle
ground between always and madvise. If the mapping is MADV_HUGEPAGE, the
page fault handler will act normally, making a hugepage if possible. If
the allocation is not MADV_HUGEPAGE, then the page fault handler will
default to the base size allocation. The caveat is that khugepaged can
still operate on pages that are not MADV_HUGEPAGE.
This allows for three things... one, applications specifically designed to
use hugepages will get them, and two, applications that don't use
hugepages can still benefit from them without aggressively inserting
THPs at every possible chance. This curbs the memory waste, and defers
the use of hugepages to khugepaged. Khugepaged can then scan the memory
for eligible collapsing. Lastly there is the added benefit for those who
want THPs but experience higher latency PFs. Now you can get base page
performance at the PF handler and Hugepage performance for those mappings
after they collapse.
Admins may want to lower max_ptes_none, if not, khugepaged may
aggressively collapse single allocations into hugepages.
TESTING:
- Built for x86_64, aarch64, ppc64le, and s390x
- selftests mm
- In [1] I provided a script [2] that has multiple access patterns
- lots of general use.
- redis testing. This test was my original case for the defer mode. What I
was able to prove was that THP=always leads to increased max_latency
cases; hence why it is recommended to disable THPs for redis servers.
However with 'defer' we dont have the max_latency spikes and can still
get the system to utilize THPs. I further tested this with the mTHP
defer setting and found that redis (and probably other jmalloc users)
can utilize THPs via defer (+mTHP defer) without a large latency
penalty and some potential gains. I uploaded some mmtest results
here[3] which compares:
stock+thp=never
stock+(m)thp=always
khugepaged-mthp + defer (max_ptes_none=64)
The results show that (m)THPs can cause some throughput regression in
some cases, but also has gains in other cases. The mTHP+defer results
have more gains and less losses over the (m)THP=always case.
V6 Changes:
- nits
- rebased dependent series and added review tags
V5 Changes:
- rebased dependent series
- added reviewed-by tag on 2/4
V4 Changes:
- Minor Documentation fixes
- rebased the dependent series [1] onto mm-unstable
commit 0e68b850b1d3 ("vmalloc: use atomic_long_add_return_relaxed()")
V3 Changes:
- Combined the documentation commits into one, and moved a section to the
khugepaged mthp patchset
V2 Changes:
- base changes on mTHP khugepaged support
- Fix selftests parsing issue
- add mTHP defer option
- add mTHP defer Documentation
[1] - https://lore.kernel.org/all/20250515032226.128900-1-npache@redhat.com/
[2] - https://gitlab.com/npache/khugepaged_mthp_test
[3] - https://people.redhat.com/npache/mthp_khugepaged_defer/testoutput2/output.h…
Nico Pache (4):
mm: defer THP insertion to khugepaged
mm: document (m)THP defer usage
khugepaged: add defer option to mTHP options
selftests: mm: add defer to thp setting parser
Documentation/admin-guide/mm/transhuge.rst | 31 +++++++---
include/linux/huge_mm.h | 18 +++++-
mm/huge_memory.c | 69 +++++++++++++++++++---
mm/khugepaged.c | 8 +--
tools/testing/selftests/mm/thp_settings.c | 1 +
tools/testing/selftests/mm/thp_settings.h | 1 +
6 files changed, 106 insertions(+), 22 deletions(-)
--
2.49.0
Nolibc is useful for selftests as the test programs can be very small,
and compiled with just a kernel crosscompiler, without userspace support.
Currently nolibc is only usable with kselftest.h, not the more
convenient to use kselftest_harness.h
This series provides this compatibility by removing the usage of problematic
libc features from the harness.
Based on nolibc/for-next.
The series is meant to be merged through the nolibc tree.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh(a)linutronix.de>
---
Changes in v4:
- Drop patches for nolibc which where already applied
- Preserve signatures of test functions for tests making assumptions about them
drop 'selftests: harness: Always provide "self" and "variant"'
add 'selftests: harness: Add "variant" and "self" to test metadata'
adapt 'selftests: harness: Stop using setjmp()/longjmp()'
- Validate test function signatures in harness selftest
- Link to v3: https://lore.kernel.org/r/20250411-nolibc-kselftest-harness-v3-0-4d9c029589…
Changes in v3:
- Send patches to correct kselftest harness maintainers
- Move harness selftest to dedicated directory
- Add harness selftest to MAINTAINERS
- Integrate harness selftest cleanup with the selftest framework
- Consistently use "kselftest harness" in commit messages
- Properly propagate kselftest harness failure
- Link to v2: https://lore.kernel.org/r/20250407-nolibc-kselftest-harness-v2-0-f8812f76e9…
Changes in v2:
- Rebase unto v6.15-rc1
- Rename internal nolibc symbols
- Handle edge case of waitpid(INT_MIN) == ESRCH
- Fix arm configurations for final testing patch
- Clean up global getopt.h variable declarations
- Add Acks from Willy
- Link to v1: https://lore.kernel.org/r/20250304-nolibc-kselftest-harness-v1-0-adca7cd231…
---
Thomas Weißschuh (14):
selftests: harness: Add kselftest harness selftest
selftests: harness: Use C89 comment style
selftests: harness: Ignore unused variant argument warning
selftests: harness: Mark functions without prototypes static
selftests: harness: Remove inline qualifier for wrappers
selftests: harness: Remove dependency on libatomic
selftests: harness: Implement test timeouts through pidfd
selftests: harness: Don't set setup_completed for fixtureless tests
selftests: harness: Move teardown conditional into test metadata
selftests: harness: Add teardown callback to test metadata
selftests: harness: Add "variant" and "self" to test metadata
selftests: harness: Stop using setjmp()/longjmp()
selftests: harness: Guard includes on nolibc
HACK: selftests/nolibc: demonstrate usage of the kselftest harness
MAINTAINERS | 1 +
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/kselftest_harness.h | 175 +-
.../testing/selftests/kselftest_harness/.gitignore | 2 +
tools/testing/selftests/kselftest_harness/Makefile | 7 +
.../selftests/kselftest_harness/harness-selftest.c | 138 ++
.../kselftest_harness/harness-selftest.expected | 64 +
.../kselftest_harness/harness-selftest.sh | 13 +
tools/testing/selftests/nolibc/Makefile | 15 +-
tools/testing/selftests/nolibc/harness-selftest.c | 1 +
tools/testing/selftests/nolibc/nolibc-test.c | 1715 +-------------------
tools/testing/selftests/nolibc/run-tests.sh | 2 +-
12 files changed, 313 insertions(+), 1821 deletions(-)
---
base-commit: 2051d3b830c0889ae55e37e9e8ff0d43a4acd482
change-id: 20250130-nolibc-kselftest-harness-8b2c8cac43bf
Best regards,
--
Thomas Weißschuh <thomas.weissschuh(a)linutronix.de>
As titled, adding version file to kselftest installation dir, so the user
of the tarball can know which kernel version the tarball belongs to.
Signed-off-by: Tianyi Cui <1997cui(a)gmail.com>
---
tools/testing/selftests/Makefile | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index a0a6ba47d600..246e9863b45b 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -291,6 +291,12 @@ ifdef INSTALL_PATH
$(MAKE) -s --no-print-directory OUTPUT=$$BUILD_TARGET COLLECTION=$$TARGET \
-C $$TARGET emit_tests >> $(TEST_LIST); \
done;
+ @if git describe HEAD > /dev/null 2>&1; then \
+ git describe HEAD > $(INSTALL_PATH)/VERSION; \
+ printf "Version saved to $(INSTALL_PATH)/VERSION\n"; \
+ else \
+ printf "Unable to get version from git describe\n"; \
+ fi
else
$(error Error: set INSTALL_PATH to use install)
endif
--
2.47.1
This started with a patch that enabled `clippy::ptr_as_ptr`. Benno
Lossin suggested I also look into `clippy::ptr_cast_constness` and I
discovered `clippy::as_ptr_cast_mut`. This series now enables all 3
lints. It also enables `clippy::as_underscore` which ensures other
pointer casts weren't missed.
As a later addition, `clippy::cast_lossless` and `clippy::ref_as_ptr`
are also enabled.
This series depends on "rust: retain pointer mut-ness in
`container_of!`"[1].
Link: https://lore.kernel.org/all/20250409-container-of-mutness-v1-1-64f472b94534… [1]
Signed-off-by: Tamir Duberstein <tamird(a)gmail.com>
---
Changes in v10:
- Move fragment from "rust: enable `clippy::ptr_cast_constness` lint" to
"rust: enable `clippy::ptr_as_ptr` lint". (Boqun Feng)
- Replace `(...).into()` with `T::from(...)` where the destination type
isn't obvious in "rust: enable `clippy::cast_lossless` lint". (Boqun
Feng)
- Link to v9: https://lore.kernel.org/r/20250416-ptr-as-ptr-v9-0-18ec29b1b1f3@gmail.com
Changes in v9:
- Replace ref-to-ptr coercion using `let` bindings with
`core::ptr::from_{ref,mut}`. (Boqun Feng).
- Link to v8: https://lore.kernel.org/r/20250409-ptr-as-ptr-v8-0-3738061534ef@gmail.com
Changes in v8:
- Use coercion to go ref -> ptr.
- rustfmt.
- Rebase on v6.15-rc1.
- Extract first commit to its own series as it is shared with other
series.
- Link to v7: https://lore.kernel.org/r/20250325-ptr-as-ptr-v7-0-87ab452147b9@gmail.com
Changes in v7:
- Add patch to enable `clippy::ref_as_ptr`.
- Link to v6: https://lore.kernel.org/r/20250324-ptr-as-ptr-v6-0-49d1b7fd4290@gmail.com
Changes in v6:
- Drop strict provenance patch.
- Fix URLs in doc comments.
- Add patch to enable `clippy::cast_lossless`.
- Rebase on rust-next.
- Link to v5: https://lore.kernel.org/r/20250317-ptr-as-ptr-v5-0-5b5f21fa230a@gmail.com
Changes in v5:
- Use `pointer::addr` in OF. (Boqun Feng)
- Add documentation on stubs. (Benno Lossin)
- Mark stubs `#[inline]`.
- Pick up Alice's RB on a shared commit from
https://lore.kernel.org/all/Z9f-3Aj3_FWBZRrm@google.com/.
- Link to v4: https://lore.kernel.org/r/20250315-ptr-as-ptr-v4-0-b2d72c14dc26@gmail.com
Changes in v4:
- Add missing SoB. (Benno Lossin)
- Use `without_provenance_mut` in alloc. (Boqun Feng)
- Limit strict provenance lints to the `kernel` crate to avoid complex
logic in the build system. This can be revisited on MSRV >= 1.84.0.
- Rebase on rust-next.
- Link to v3: https://lore.kernel.org/r/20250314-ptr-as-ptr-v3-0-e7ba61048f4a@gmail.com
Changes in v3:
- Fixed clippy warning in rust/kernel/firmware.rs. (kernel test robot)
Link: https://lore.kernel.org/all/202503120332.YTCpFEvv-lkp@intel.com/
- s/as u64/as bindings::phys_addr_t/g. (Benno Lossin)
- Use strict provenance APIs and enable lints. (Benno Lossin)
- Link to v2: https://lore.kernel.org/r/20250309-ptr-as-ptr-v2-0-25d60ad922b7@gmail.com
Changes in v2:
- Fixed typo in first commit message.
- Added additional patches, converted to series.
- Link to v1: https://lore.kernel.org/r/20250307-ptr-as-ptr-v1-1-582d06514c98@gmail.com
---
Tamir Duberstein (6):
rust: enable `clippy::ptr_as_ptr` lint
rust: enable `clippy::ptr_cast_constness` lint
rust: enable `clippy::as_ptr_cast_mut` lint
rust: enable `clippy::as_underscore` lint
rust: enable `clippy::cast_lossless` lint
rust: enable `clippy::ref_as_ptr` lint
Makefile | 6 ++++++
drivers/gpu/drm/drm_panic_qr.rs | 2 +-
rust/bindings/lib.rs | 3 +++
rust/kernel/alloc/allocator_test.rs | 2 +-
rust/kernel/alloc/kvec.rs | 4 ++--
rust/kernel/block/mq/operations.rs | 2 +-
rust/kernel/block/mq/request.rs | 6 +++---
rust/kernel/device.rs | 4 ++--
rust/kernel/device_id.rs | 4 ++--
rust/kernel/devres.rs | 19 ++++++++++---------
rust/kernel/dma.rs | 6 +++---
rust/kernel/error.rs | 2 +-
rust/kernel/firmware.rs | 3 ++-
rust/kernel/fs/file.rs | 2 +-
rust/kernel/io.rs | 18 +++++++++---------
rust/kernel/kunit.rs | 11 +++++++----
rust/kernel/list/impl_list_item_mod.rs | 2 +-
rust/kernel/miscdevice.rs | 2 +-
rust/kernel/net/phy.rs | 4 ++--
rust/kernel/of.rs | 6 +++---
rust/kernel/pci.rs | 11 +++++++----
rust/kernel/platform.rs | 4 +++-
rust/kernel/print.rs | 6 +++---
rust/kernel/seq_file.rs | 2 +-
rust/kernel/str.rs | 14 +++++++-------
rust/kernel/sync/poll.rs | 2 +-
rust/kernel/time/hrtimer/pin.rs | 2 +-
rust/kernel/time/hrtimer/pin_mut.rs | 2 +-
rust/kernel/uaccess.rs | 4 ++--
rust/kernel/workqueue.rs | 12 ++++++------
rust/uapi/lib.rs | 3 +++
31 files changed, 96 insertions(+), 74 deletions(-)
---
base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
change-id: 20250307-ptr-as-ptr-21b1867fc4d4
prerequisite-change-id: 20250409-container-of-mutness-b153dab4388d:v1
prerequisite-patch-id: 53d5889db599267f87642bb0ae3063c29bc24863
Best regards,
--
Tamir Duberstein <tamird(a)gmail.com>
The test file for the IR decoder used single-line comments at the top
to document its purpose and licensing, which is inconsistent with the style
used throughout the Linux kernel.
in this patch i converted the file header to a proper multi-line comment block
(/*) that aligns with standard kernel practices. This improves
readability, consistency across selftests, and ensures the license and
documentation are clearly visible in a familiar format.
No functional changes have been made.
Signed-off-by: Abdelrahman Fekry <Abdelrahmanfekry375(a)gmail.com>
---
tools/testing/selftests/ir/ir_loopback.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/ir/ir_loopback.c b/tools/testing/selftests/ir/ir_loopback.c
index f4a15cbdd5ea..2de4a6296f35 100644
--- a/tools/testing/selftests/ir/ir_loopback.c
+++ b/tools/testing/selftests/ir/ir_loopback.c
@@ -1,14 +1,15 @@
// SPDX-License-Identifier: GPL-2.0
-// test ir decoder
-//
-// Copyright (C) 2018 Sean Young <sean(a)mess.org>
-
-// When sending LIRC_MODE_SCANCODE, the IR will be encoded. rc-loopback
-// will send this IR to the receiver side, where we try to read the decoded
-// IR. Decoding happens in a separate kernel thread, so we will need to
-// wait until that is scheduled, hence we use poll to check for read
-// readiness.
-
+/* Copyright (C) 2018 Sean Young <sean(a)mess.org>
+ *
+ * Selftest for IR decoder
+ *
+ *
+ * When sending LIRC_MODE_SCANCODE, the IR will be encoded. rc-loopback
+ * will send this IR to the receiver side, where we try to read the decoded
+ * IR. Decoding happens in a separate kernel thread, so we will need to
+ * wait until that is scheduled, hence we use poll to check for read
+ * readiness.
+*/
#include <linux/lirc.h>
#include <errno.h>
#include <stdio.h>
--
2.25.1
Hello,
this series is a revival of Xu Kuhoai's work to enable larger arguments
count for BPF programs on ARM64 ([1]). His initial series received some
positive feedback, but lacked some specific case handling around
arguments alignment (see AAPCS64 C.14 rule in section 6.8.2, [2]). There
as been another attempt from Puranjay Mohan, which was unfortunately
missing the same thing ([3]). Since there has been some time between
those series and this new one, I chose to send it as a new series
rather than a new revision of the existing series.
To support the increased argument counts and arguments larger than
registers size (eg: structures), the trampoline does the following:
- for bpf programs: arguments are retrieved from both registers and the
function stack, and pushed in the trampoline stack as an array of u64
to generate the programs context. It is then passed by pointer to the
bpf programs
- when the trampoline is in charge of calling the original function: it
restores the registers content, and generates a new stack layout for
the additional arguments that do not fit in registers.
This new attempt is based on Xu's series and aims to handle the
missing alignment concern raised in the reviews discussions. The main
novelties are then around arguments alignments:
- the first commit is exposing some new info in the BTF function model
passed to the JIT compiler to allow it to deduce the needed alignment
when configuring the trampoline stack
- the second commit is taken from Xu's series, and received the
following modifications:
- the calc_aux_args computes an expected alignment for each argument
- the calc_aux_args computes two different stack space sizes: the one
needed to store the bpf programs context, and the original function
stacked arguments (which needs alignment). Those stack sizes are in
bytes instead of "slots"
- when saving/restoring arguments for bpf program or for the original
function, make sure to align the load/store accordingly, when
relevant
- a few typos fixes and some rewording, raised by the review on the
original series
- the last commit introduces some explicit tests that ensure that the
needed alignment is enforced by the trampoline
I marked the series as RFC because it appears that the new tests trigger
some failures in CI on x86 and s390, despite the series not touching any
code related to those architectures. Some very early investigation/gdb
debugging on the x86 side seems to hint that it could be related to the
same missing alignment too (based on section 3.2.3 in [4], and so the
x86 trampoline would need the same alignment handling ?). For s390 it
looks less clear, as all values captured from the bpf test program are
set to 0 in the CI output, and I don't have the proper setup yet to
check the low level details. I am tempted to isolate those new tests
(which were actually useful to spot real issues while tuning the ARM64
trampoline) and add them to the relevant DENYLIST files for x86/s390,
but I guess this is not the right direction, so I would gladly take a
second opinion on this.
[1] https://lore.kernel.org/all/20230917150752.69612-1-xukuohai@huaweicloud.com…
[2] https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst#id82
[3] https://lore.kernel.org/bpf/20240705125336.46820-1-puranjay@kernel.org/
[4] https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore(a)bootlin.com>
---
Alexis Lothoré (eBPF Foundation) (3):
bpf: add struct largest member size in func model
bpf/selftests: add tests to validate proper arguments alignment on ARM64
bpf/selftests: enable tracing tests for ARM64
Xu Kuohai (1):
bpf, arm64: Support up to 12 function arguments
arch/arm64/net/bpf_jit_comp.c | 235 ++++++++++++++++-----
include/linux/bpf.h | 1 +
kernel/bpf/btf.c | 25 +++
tools/testing/selftests/bpf/DENYLIST.aarch64 | 3 -
.../selftests/bpf/prog_tests/tracing_struct.c | 23 ++
tools/testing/selftests/bpf/progs/tracing_struct.c | 10 +-
.../selftests/bpf/progs/tracing_struct_many_args.c | 67 ++++++
.../testing/selftests/bpf/test_kmods/bpf_testmod.c | 50 +++++
8 files changed, 357 insertions(+), 57 deletions(-)
---
base-commit: 91e7eb701b4bc389e7ddfd80ef6e82d1a6d2d368
change-id: 20250220-many_args_arm64-8bd3747e6948
Best regards,
--
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com