diff options
Diffstat (limited to 'linux-Simplify-get_nprocs.patch')
| -rw-r--r-- | linux-Simplify-get_nprocs.patch | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/linux-Simplify-get_nprocs.patch b/linux-Simplify-get_nprocs.patch new file mode 100644 index 0000000..55c49b2 --- /dev/null +++ b/linux-Simplify-get_nprocs.patch @@ -0,0 +1,216 @@ +From cda99af14e82b4bb6abaecd717ebe3b57c0aa534 Mon Sep 17 00:00:00 2001 +From: Adhemerval Zanella <adhemerval.zanella@linaro.org> +Date: Mon, 6 Sep 2021 12:28:24 -0300 +Subject: [PATCH] linux: Simplify get_nprocs + +This patch simplifies the memory allocation code and uses the sched +routines instead of reimplement it. This still uses a stack +allocation buffer, so it can be used on malloc initialization code. + +Linux currently supports at maximum of 4096 cpus for most architectures: + +$ find -iname Kconfig | xargs git grep -A10 -w NR_CPUS | grep -w range +arch/alpha/Kconfig- range 2 32 +arch/arc/Kconfig- range 2 4096 +arch/arm/Kconfig- range 2 16 if DEBUG_KMAP_LOCAL +arch/arm/Kconfig- range 2 32 if !DEBUG_KMAP_LOCAL +arch/arm64/Kconfig- range 2 4096 +arch/csky/Kconfig- range 2 32 +arch/hexagon/Kconfig- range 2 6 if SMP +arch/ia64/Kconfig- range 2 4096 +arch/mips/Kconfig- range 2 256 +arch/openrisc/Kconfig- range 2 32 +arch/parisc/Kconfig- range 2 32 +arch/riscv/Kconfig- range 2 32 +arch/s390/Kconfig- range 2 512 +arch/sh/Kconfig- range 2 32 +arch/sparc/Kconfig- range 2 32 if SPARC32 +arch/sparc/Kconfig- range 2 4096 if SPARC64 +arch/um/Kconfig- range 1 1 +arch/x86/Kconfig-# [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range. +arch/x86/Kconfig- range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END +arch/xtensa/Kconfig- range 2 32 + +With x86 supporting 8192: + +arch/x86/Kconfig + 976 config NR_CPUS_RANGE_END + 977 int + 978 depends on X86_64 + 979 default 8192 if SMP && CPUMASK_OFFSTACK + 980 default 512 if SMP && !CPUMASK_OFFSTACK + 981 default 1 if !SMP + +So using a maximum of 32k cpu should cover all cases (and I would +expect once we start to have many more CPUs that Linux would provide +a more straightforward way to query for such information). + +A test is added to check if sched_getaffinity can successfully return +with large buffers. + +Checked on x86_64-linux-gnu and i686-linux-gnu. + +Reviewed-by: Florian Weimer <fweimer@redhat.com> +(cherry picked from commit 33099d72e41cf8a129b362e9709eb2be9372d844) +--- + posix/Makefile | 3 +- + posix/tst-sched_getaffinity.c | 48 +++++++++++++++++++++++++ + sysdeps/unix/sysv/linux/getsysstats.c | 68 ++++++++++------------------------- + 3 files changed, 68 insertions(+), 51 deletions(-) + create mode 100644 posix/tst-sched_getaffinity.c + +diff --git a/posix/Makefile b/posix/Makefile +index 059efb3..09460a2 100644 +--- a/posix/Makefile ++++ b/posix/Makefile +@@ -107,7 +107,8 @@ tests := test-errno tstgetopt testfnm runtests runptests \ + tst-sysconf-empty-chroot tst-glob_symlinks tst-fexecve \ + tst-glob-tilde test-ssize-max tst-spawn4 bug-regex37 \ + bug-regex38 tst-regcomp-truncated tst-spawn-chdir \ +- tst-wordexp-nocmd tst-execveat tst-spawn5 ++ tst-wordexp-nocmd tst-execveat tst-spawn5 \ ++ tst-sched_getaffinity + + # Test for the glob symbol version that was replaced in glibc 2.27. + ifeq ($(have-GLIBC_2.26)$(build-shared),yesyes) +diff --git a/posix/tst-sched_getaffinity.c b/posix/tst-sched_getaffinity.c +new file mode 100644 +index 0000000..db9d517 +--- /dev/null ++++ b/posix/tst-sched_getaffinity.c +@@ -0,0 +1,48 @@ ++/* Tests for sched_getaffinity with large buffers. ++ Copyright (C) 2021 Free Software Foundation, Inc. ++ This file is part of the GNU C Library. ++ ++ The GNU C Library is free software; you can redistribute it and/or ++ modify it under the terms of the GNU Lesser General Public ++ License as published by the Free Software Foundation; either ++ version 2.1 of the License, or (at your option) any later version. ++ ++ The GNU C Library is distributed in the hope that it will be useful, ++ but WITHOUT ANY WARRANTY; without even the implied warranty of ++ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ++ Lesser General Public License for more details. ++ ++ You should have received a copy of the GNU Lesser General Public ++ License along with the GNU C Library; if not, see ++ <https://www.gnu.org/licenses/>. */ ++ ++#include <array_length.h> ++#include <sched.h> ++#include <support/check.h> ++ ++/* NB: this test may fail on system with more than 32k cpus. */ ++ ++static int ++do_test (void) ++{ ++ /* The values are larger than the default cpu_set_t. */ ++ const int bufsize[] = { 1<<11, 1<<12, 1<<13, 1<<14, 1<<15, 1<<16, 1<<17 }; ++ int cpucount[array_length (bufsize)]; ++ ++ for (int i = 0; i < array_length (bufsize); i++) ++ { ++ cpu_set_t *cpuset = CPU_ALLOC (bufsize[i]); ++ TEST_VERIFY (cpuset != NULL); ++ size_t size = CPU_ALLOC_SIZE (bufsize[i]); ++ TEST_COMPARE (sched_getaffinity (0, size, cpuset), 0); ++ cpucount[i] = CPU_COUNT_S (size, cpuset); ++ CPU_FREE (cpuset); ++ } ++ ++ for (int i = 0; i < array_length (cpucount) - 1; i++) ++ TEST_COMPARE (cpucount[i], cpucount[i + 1]); ++ ++ return 0; ++} ++ ++#include <support/test-driver.c> +diff --git a/sysdeps/unix/sysv/linux/getsysstats.c b/sysdeps/unix/sysv/linux/getsysstats.c +index 120ce1b..61d20e7 100644 +--- a/sysdeps/unix/sysv/linux/getsysstats.c ++++ b/sysdeps/unix/sysv/linux/getsysstats.c +@@ -29,61 +29,29 @@ + #include <sys/sysinfo.h> + #include <sysdep.h> + +-/* Compute the population count of the entire array. */ +-static int +-__get_nprocs_count (const unsigned long int *array, size_t length) +-{ +- int count = 0; +- for (size_t i = 0; i < length; ++i) +- if (__builtin_add_overflow (count, __builtin_popcountl (array[i]), +- &count)) +- return INT_MAX; +- return count; +-} +- +-/* __get_nprocs with a large buffer. */ +-static int +-__get_nprocs_large (void) +-{ +- /* This code cannot use scratch_buffer because it is used during +- malloc initialization. */ +- size_t pagesize = GLRO (dl_pagesize); +- unsigned long int *page = __mmap (0, pagesize, PROT_READ | PROT_WRITE, +- MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); +- if (page == MAP_FAILED) +- return 2; +- int r = INTERNAL_SYSCALL_CALL (sched_getaffinity, 0, pagesize, page); +- int count; +- if (r > 0) +- count = __get_nprocs_count (page, pagesize / sizeof (unsigned long int)); +- else if (r == -EINVAL) +- /* One page is still not enough to store the bits. A more-or-less +- arbitrary value. This assumes t hat such large systems never +- happen in practice. */ +- count = GLRO (dl_pagesize) * CHAR_BIT; +- else +- count = 2; +- __munmap (page, GLRO (dl_pagesize)); +- return count; +-} +- + int + __get_nprocs (void) + { +- /* Fast path for most systems. The kernel expects a buffer size +- that is a multiple of 8. */ +- unsigned long int small_buffer[1024 / CHAR_BIT / sizeof (unsigned long int)]; +- int r = INTERNAL_SYSCALL_CALL (sched_getaffinity, 0, +- sizeof (small_buffer), small_buffer); ++ enum ++ { ++ max_num_cpus = 32768, ++ cpu_bits_size = CPU_ALLOC_SIZE (32768) ++ }; ++ ++ /* This cannot use malloc because it is used on malloc initialization. */ ++ __cpu_mask cpu_bits[cpu_bits_size / sizeof (__cpu_mask)]; ++ int r = INTERNAL_SYSCALL_CALL (sched_getaffinity, 0, cpu_bits_size, ++ cpu_bits); + if (r > 0) +- return __get_nprocs_count (small_buffer, r / sizeof (unsigned long int)); ++ return CPU_COUNT_S (cpu_bits_size, (cpu_set_t*) cpu_bits); + else if (r == -EINVAL) +- /* The kernel requests a larger buffer to store the data. */ +- return __get_nprocs_large (); +- else +- /* Some other error. 2 is conservative (not a uniprocessor +- system, so atomics are needed). */ +- return 2; ++ /* The input buffer is still not enough to store the number of cpus. This ++ is an arbitrary values assuming such systems should be rare and there ++ is no offline cpus. */ ++ return max_num_cpus; ++ /* Some other error. 2 is conservative (not a uniprocessor system, so ++ atomics are needed). */ ++ return 2; + } + libc_hidden_def (__get_nprocs) + weak_alias (__get_nprocs, get_nprocs) +-- +1.8.3.1 + |