Running the executable mremap_test generated by compiling mremap_test.c,
located at tools/testing/selftests/vm, using the makefile provided in
tools/testing/selftests/vm gives an error of segmentation fault.
The error happens during the execution of the following test case (line
298):
test_cases[4] = MAKE_TEST(_1MB, PTE, _2MB, NON_OVERLAPPING,
EXPECT_SUCCESS, "2MB mremap - Source 1MB-aligned, Destination PTE-aligned");
The seg fault happens on line 145:
dest_addr = mremap(src_addr, c.region_size, c.region_size,
MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);
The makefile compiles mremap_test.c using the command: gcc -Wall -I
../../../../usr/include -no-pie mremap_test.c -lrt -lpthread -o
/home/guest/shared/linux-kernel/tools/testing/selftests/vm/mremap_test
I was able to run mremap_test without errors when compiling it without
the -no-pie flag.
The frequency of the rss_stat trace event is known to be of the same
magnitude as that of the sched_switch event on Android devices. This can
cause flooding of the trace buffer with rss_stat traces leading to a
decreased trace buffer capacity and loss of data.
If it is not necessary to monitor very small changes in rss (as is the
case in Android) then the rss_stat tracepoint can be throttled to only
emit the event once there is a large enough change in the rss size.
The original patch that introduced the rss_stat tracepoint also proposed
a fixed throttling mechanism that only emits the rss_stat event
when the rss size crosses a 512KB boundary. It was concluded that more
generic support for this type of filtering/throttling was need, so that
it can be applied to any trace event. [1]
>From the discussion in [1], histogram triggers seemed the most likely
candidate to support this type of throttling. For instance to achieve the
same throttling as was proposed in [1]:
(1) Create a histogram variable to save the 512KB bucket of the rss size
(2) Use the onchange handler to generate a synthetic event when the
rss size bucket changes.
The only missing pieces to support such a hist trigger are:
(1) Support for setting a hist variable to a specific value -- to set
the bucket size / granularity.
(2) Support for division arithmetic operation -- to determine the
corresponding bucket for an rss size.
This series extends histogram trigger expressions to:
(1) Allow assigning numeric literals to hist variable (eg. x=1234)
and using literals directly in expressions (eg. x=size/1234)
(2) Support division and multiplication in hist expressions.
(eg. a=$x/$y*z); and
(3) Fixes expression parsing for non-associative operators: subtraction
and division. (eg. 8-4-2 should be 2 not 6)
The rss_stat event can then be throttled using histogram triggers as
below:
# Create a synthetic event to monitor instead of the high frequency
# rss_stat event
echo 'rss_stat_throttled unsigned int mm_id; unsigned int curr;
int member; long size' >> tracing/synthetic_events
# Create a hist trigger that emits the synthetic rss_stat_throttled
# event only when the rss size crosses a 512KB boundary.
echo 'hist:keys=common_pid:bucket=size/0x80000:onchange($bucket)
.rss_stat_throttled(mm_id,curr,member,size)'
>> events/kmem/rss_stat/trigger
------ Test Results ------
Histograms can also be used to evaluate the effectiveness of this
throttling by noting the Total Hits on each trigger:
echo 'hist:keys=common_pid' >> events/sched/sched_switch/trigger
echo 'hist:keys=common_pid' >> events/kmem/rss_stat/trigger
echo 'hist:keys=common_pid'
>> events/synthetic/rss_stat_throttled/trigger
Allowing the above example (512KB granularity) run for 5 minutes on
an arm64 device with 5.10 kernel:
sched_switch : total hits = 147153
rss_stat : total hits = 38863
rss_stat_throttled: total hits = 2409
The synthetic rss_stat_throttled event is ~16x less frequent than the
rss_stat event when using a 512KB granularity.
The results are more pronounced when rss size is changing at a higher
rate in small increments. For instance the following results were obtained
by recording the hits on the above events for a run of Android's
lmkd_unit_test [2], which continually forks processes that map anonymous
memory until there is an oom kill:
sched_switch : total hits = 148832
rss_stat : total hits = 4754802
rss_stat_throttled: total hits = 96214
In this stress this, the synthetic rss_stat_throttled event is ~50x less
frequent than the rss_stat event when using a 512KB granularity.
[1] https://lore.kernel.org/lkml/20190903200905.198642-1-joel@joelfernandes.org/
[2] https://cs.android.com/android/platform/superproject/+/master:system/memory…
Signed-off-by: Kalesh Singh <kaleshsingh(a)google.com>
Kalesh Singh (5):
tracing: Add support for creating hist trigger variables from literal
tracing: Add division and multiplication support for hist triggers
tracing: Fix operator precedence for hist triggers expression
tracing/selftests: Add tests for hist trigger expression parsing
tracing/histogram: Document expression arithmetic and constants
Documentation/trace/histogram.rst | 14 +
kernel/trace/trace_events_hist.c | 318 +++++++++++++++---
.../testing/selftests/ftrace/test.d/functions | 4 +-
.../trigger/trigger-hist-expressions.tc | 73 ++++
4 files changed, 357 insertions(+), 52 deletions(-)
create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-expressions.tc
base-commit: 3ca706c189db861b2ca2019a0901b94050ca49d8
--
2.33.0.309.g3052b89438-goog
This series provides initial support for the ARMv9 Scalable Matrix
Extension (SME). SME takes the approach used for vectors in SVE and
extends this to provide architectural support for matrix operations. A
more detailed overview can be found in [1].
For the kernel SME can be thought of as a series of features which are
intended to be used together by applications but operate mostly
orthogonally:
- The ZA matrix register.
- Streaming mode, in which ZA can be accessed and a subset of SVE
features are available.
- A second vector length, used for streaming mode SVE and ZA and
controlled using a similar interface to that for SVE.
- TPIDR2, a new userspace controllable system register intended for use
by the C library for storing context related to the ZA ABI.
A substantial part of the series is dedicated to refactoring the
existing SVE support so that we don't need to duplicate code for
handling vector lengths and the SVE registers, this involves creating an
array of vector types and making the users take the vector type as a
parameter. I'm not 100% happy with this but wasn't able to come up with
anything better, duplicating code definitely felt like a bad idea so
this felt like the least bad thing. If this approach makes sense to
people it might make sense to split this off into a separate series
and/or merge it while the rest is pending review to try to make things a
little more digestable, the series is very large so it'd probably make
things easier to digest if some of the preparatory refactoring could be
merged before the rest is ready.
One feature of the architecture of particular note is that switching
to and from streaming mode may change the size of and invalidate the
contents of the SVE registers, and when in streaming mode the FFR is not
accessible. This complicates aspects of the ABI like signal handling
and ptrace.
This initial implementation is mainly intended to get the ABI in place,
there are several areas which will be worked on going forwards - some of
these will be blockers, others could be handled in followup serieses:
- KVM is not currently supported and we depend on !KVM, this is
obviously not good - in hopefully the next version I will add support
for coexisting with KVM and then in a subsequent series implement
support for use of SME by KVM guests.
- It is likely some build configurations have issues, I've not fully
checked this yet. In general testing is still ongoing, I anticipate
finding and fixing some issues in the implementation.
- No support is currently provided for scheduler control of SME or SME
applications, given the size of the SME register state the context
switch overhead may be noticable so this may be needed especially for
real time applications. Similar concerns already exist for larger
SVE vector lengths but are amplified for SME, particularly as the
vector length increases.
- There has been no work on optimising the performance of anything the
kernel does.
It is not expected that any systems will be encountered that support SME
but not SVE, SME is an ARMv9 feature and SVE is mandatory for ARMv9.
The code attempts to handle any such systems that are encountered but
this hasn't been tested extensively.
Due to dependencies on kselftest changes already upstreamed this series
is based on for-next/kselftest in the arm64 tree.
v2:
- Fix several issues with !SME and !SVE configurations.
- Preserve TPIDR2 when creating a new thread/process unless
CLONE_SETTLS is set.
- Report traps due to using features in an invalid mode as SIGILL.
- Spell out streaming mode behaviour in SVE ABI documentation more
directly.
- Document TPIDR2 in the ABI document.
- Use SMSTART and SMSTOP rather than read/modify/write sequences.
- Rework logic for exiting streaming mode on syscall.
- Don't needlessly initialise SVCR on access trap.
- Always restore SME VL for userspace if SME traps are disabled.
- Only yield to encourage preemption every 128 iterations in za-test,
otherwise do a getpid(), and validate SVCR after syscall.
- Leave streaming mode disabled except when reading the vector length
in za-test, and disable ZA after detecting a mismatch.
- Add SME support to vlset.
- Clarifications and typo fixes in comments.
- Move sme_alloc() forward declaration back a patch.
[1] https://community.arm.com/developer/ip-products/processors/b/processors-ip-…
Mark Brown (42):
arm64/fp: Reindent fpsimd_save()
arm64/sve: Remove sve_load_from_fpsimd_state()
arm64/sve: Make sve_state_size() static
arm64/sve: Make access to FFR optional
arm64/sve: Rename find_supported_vector_length()
arm64/sve: Use accessor functions for vector lengths in thread_struct
arm64/sve: Put system wide vector length information into structs
arm64/sve: Explicitly load vector length when restoring SVE state
arm64/sve: Track vector lengths for tasks in an array
arm64/sve: Make sysctl interface for SVE reusable by SME
arm64/sve: Generalise vector length configuration prctl() for SME
kselftest/arm64: Parameterise ptrace vector length information
kselftest/arm64: Allow signal tests to trigger from a function
tools/nolibc: Implement gettid()
arm64/sme: Provide ABI documentation for SME
arm64/sme: System register and exception syndrome definitions
arm64/sme: Define macros for manually encoding SME instructions
arm64/sme: Early CPU setup for SME
arm64/sme: Basic enumeration support
arm64/sme: Identify supported SME vector lengths at boot
arm64/sme: Implement sysctl to set the default vector length
arm64/sme: Implement vector length configuration prctl()s
arm64/sme: Implement support for TPIDR2
arm64/sme: Implement SVCR context switching
arm64/sme: Implement streaming SVE context switching
arm64/sme: Implement ZA context switching
arm64/sme: Implement traps and syscall handling for SME
arm64/sme: Implement streaming SVE signal handling
arm64/sme: Implement ZA signal handling
arm64/sme: Implement ptrace support for streaming mode SVE registers
arm64/sme: Add ptrace support for ZA
arm64/sme: Disable streaming mode and ZA when flushing CPU state
arm64/sme: Save and restore streaming mode over EFI runtime calls
arm64/sme: Provide Kconfig for SME
kselftest/arm64: sme: Add streaming SME support to vlset
kselftest/arm64: Add tests for TPIDR2
kselftest/arm64: Extend vector configuration API tests to cover SME
kselftest/arm64: sme: Provide streaming mode SVE stress test
kselftest/arm64: Add stress test for SME ZA context switching
kselftest/arm64: signal: Add SME signal handling tests
kselftest/arm64: Add streaming SVE to SVE ptrace tests
kselftest/arm64: Add coverage for the ZA ptrace interface
Documentation/arm64/elf_hwcaps.rst | 29 +
Documentation/arm64/index.rst | 1 +
Documentation/arm64/sme.rst | 428 +++++++++
Documentation/arm64/sve.rst | 69 +-
arch/arm64/Kconfig | 11 +
arch/arm64/include/asm/cpu.h | 4 +
arch/arm64/include/asm/cpufeature.h | 18 +
arch/arm64/include/asm/el2_setup.h | 36 +
arch/arm64/include/asm/esr.h | 13 +-
arch/arm64/include/asm/exception.h | 1 +
arch/arm64/include/asm/fpsimd.h | 222 ++++-
arch/arm64/include/asm/fpsimdmacros.h | 94 +-
arch/arm64/include/asm/hwcap.h | 7 +
arch/arm64/include/asm/kvm_arm.h | 1 +
arch/arm64/include/asm/processor.h | 67 +-
arch/arm64/include/asm/sysreg.h | 53 +
arch/arm64/include/asm/thread_info.h | 4 +-
arch/arm64/include/uapi/asm/hwcap.h | 7 +
arch/arm64/include/uapi/asm/ptrace.h | 69 +-
arch/arm64/include/uapi/asm/sigcontext.h | 55 +-
arch/arm64/kernel/cpufeature.c | 96 +-
arch/arm64/kernel/cpuinfo.c | 12 +
arch/arm64/kernel/entry-common.c | 10 +
arch/arm64/kernel/entry-fpsimd.S | 63 +-
arch/arm64/kernel/fpsimd.c | 904 ++++++++++++++----
arch/arm64/kernel/process.c | 28 +-
arch/arm64/kernel/ptrace.c | 358 ++++++-
arch/arm64/kernel/signal.c | 189 +++-
arch/arm64/kernel/syscall.c | 43 +-
arch/arm64/kernel/traps.c | 1 +
arch/arm64/kvm/fpsimd.c | 3 +-
arch/arm64/kvm/hyp/fpsimd.S | 6 +-
arch/arm64/kvm/reset.c | 14 +-
arch/arm64/tools/cpucaps | 1 +
include/uapi/linux/elf.h | 2 +
include/uapi/linux/prctl.h | 9 +
kernel/sys.c | 12 +
tools/include/nolibc/nolibc.h | 18 +
tools/testing/selftests/arm64/Makefile | 2 +-
tools/testing/selftests/arm64/abi/.gitignore | 1 +
tools/testing/selftests/arm64/abi/Makefile | 13 +
tools/testing/selftests/arm64/abi/tpidr2.c | 298 ++++++
tools/testing/selftests/arm64/fp/.gitignore | 4 +
tools/testing/selftests/arm64/fp/Makefile | 12 +-
tools/testing/selftests/arm64/fp/rdvl-sme.c | 14 +
tools/testing/selftests/arm64/fp/rdvl.S | 16 +
tools/testing/selftests/arm64/fp/rdvl.h | 1 +
tools/testing/selftests/arm64/fp/ssve-stress | 59 ++
tools/testing/selftests/arm64/fp/sve-ptrace.c | 230 +++--
tools/testing/selftests/arm64/fp/sve-test.S | 30 +
tools/testing/selftests/arm64/fp/vec-syscfg.c | 10 +
tools/testing/selftests/arm64/fp/vlset.c | 10 +-
tools/testing/selftests/arm64/fp/za-ptrace.c | 353 +++++++
tools/testing/selftests/arm64/fp/za-stress | 59 ++
tools/testing/selftests/arm64/fp/za-test.S | 582 +++++++++++
.../testing/selftests/arm64/signal/.gitignore | 2 +
.../selftests/arm64/signal/test_signals.h | 2 +
.../arm64/signal/test_signals_utils.c | 5 +-
.../testcases/fake_sigreturn_sme_change_vl.c | 92 ++
.../arm64/signal/testcases/sme_trap_za.c | 36 +
.../selftests/arm64/signal/testcases/sme_vl.c | 70 ++
.../arm64/signal/testcases/ssve_regs.c | 129 +++
62 files changed, 4573 insertions(+), 415 deletions(-)
create mode 100644 Documentation/arm64/sme.rst
create mode 100644 tools/testing/selftests/arm64/abi/.gitignore
create mode 100644 tools/testing/selftests/arm64/abi/Makefile
create mode 100644 tools/testing/selftests/arm64/abi/tpidr2.c
create mode 100644 tools/testing/selftests/arm64/fp/rdvl-sme.c
create mode 100644 tools/testing/selftests/arm64/fp/ssve-stress
create mode 100644 tools/testing/selftests/arm64/fp/za-ptrace.c
create mode 100644 tools/testing/selftests/arm64/fp/za-stress
create mode 100644 tools/testing/selftests/arm64/fp/za-test.S
create mode 100644 tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_sme_change_vl.c
create mode 100644 tools/testing/selftests/arm64/signal/testcases/sme_trap_za.c
create mode 100644 tools/testing/selftests/arm64/signal/testcases/sme_vl.c
create mode 100644 tools/testing/selftests/arm64/signal/testcases/ssve_regs.c
base-commit: 0ba1ce1e86052deea3f115285802ce8ffff3b152
--
2.30.2