From patchwork Tue Sep 7 12:22:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adhemerval Zanella X-Patchwork-Id: 44882 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id B42BA385E82E for ; Tue, 7 Sep 2021 12:24:07 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org B42BA385E82E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1631017447; bh=liG1REC4YvqfZ9ESnrmJuIPu3gPIKaCLtiJKJBq6fCs=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=QqKJxleNGZ1REw5C8/X3wNJQAxNvUbMZ3ZfDLVTLP/LKLsNvmhsVQWZKHRIF0xRs/ esiuFMlEHSyv8dJ7XF65BAFRdBIJp5vZl/8jl8TQIQv7E10MAjNRnVx94chiDYUIl8 rT0gUc6CHmIjRi0SBEfmaFkHNZL2CrIngoxWxyLk= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-qt1-x836.google.com (mail-qt1-x836.google.com [IPv6:2607:f8b0:4864:20::836]) by sourceware.org (Postfix) with ESMTPS id A461E3858003 for ; Tue, 7 Sep 2021 12:23:04 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org A461E3858003 Received: by mail-qt1-x836.google.com with SMTP id r21so7703489qtw.11 for ; Tue, 07 Sep 2021 05:23:04 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=liG1REC4YvqfZ9ESnrmJuIPu3gPIKaCLtiJKJBq6fCs=; b=R/DEzt9daxlAkDqP9CmGW6r2TUXPMWCRQ7wm7couqkYnSSAUnRdZbxogCBPuQeZ/gA 6TkaDGhX95JDFQrgdXVXslUEN3hthNrKdnu2/4oE6ASCykGosA9fPFIv4No7jqx/exH4 FhterKBH5/Vo74GTwCE+YXxkYt4ixUW6DP+7cZUnUZ2c4Lcc8elQWgEqPiZ8SCLX2cDG Bm3dQiN7mbLJ/iSGIINNxL4Pu99nJlJf+TK4ly3mPIs3OrMLJu1Q6O6IsvzysL8ynKVh p8sdYk/v2Dz1/PfcDyR8GO3SRopRCsYHy/8T0skZ8hhmJZO8CxrQ4D3bvNqYbD1Ux8UJ 6OOg== X-Gm-Message-State: AOAM531DtpubmLP2oIhYSCvrZkzfhKJ6kINiOSBQFDBVbWS95Gb0Q1F3 BEIZujrhXMhEfx0ncldQzeOkmOljPqiQvg== X-Google-Smtp-Source: ABdhPJywAD25WXTf6gm4a7t/EiHwYeTKHcqc5Iktmny0JzXtlHGNFjaKA7y5Shiy+3lIoLic+nmicQ== X-Received: by 2002:a05:622a:1908:: with SMTP id w8mr15320505qtc.269.1631017384143; Tue, 07 Sep 2021 05:23:04 -0700 (PDT) Received: from birita.. ([2804:431:c7cb:733d:f360:5bf3:9813:d8f5]) by smtp.gmail.com with ESMTPSA id r18sm6902148qtm.96.2021.09.07.05.23.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Sep 2021 05:23:03 -0700 (PDT) To: libc-alpha@sourceware.org Subject: [PATCH v2 1/3] misc: Add __get_nprocs_sched Date: Tue, 7 Sep 2021 09:22:57 -0300 Message-Id: <20210907122259.79800-2-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210907122259.79800-1-adhemerval.zanella@linaro.org> References: <20210907122259.79800-1-adhemerval.zanella@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-12.0 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Adhemerval Zanella via Libc-alpha From: Adhemerval Zanella Reply-To: Adhemerval Zanella Cc: Florian Weimer , Nicolas Saenz Julienne Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" This is an internal function meant to return the number of avaliable processor where the process can scheduled, different than the __get_nprocs which returns a the system available online CPU. The Linux implementation currently only calls __get_nprocs(), which in tuns calls sched_getaffinity. Reviewed-by: Florian Weimer --- include/sys/sysinfo.h | 7 ++++++- malloc/arena.c | 2 +- misc/getsysstats.c | 6 ++++++ sysdeps/mach/getsysstats.c | 6 ++++++ sysdeps/unix/sysv/linux/getsysstats.c | 6 ++++++ 5 files changed, 25 insertions(+), 2 deletions(-) diff --git a/include/sys/sysinfo.h b/include/sys/sysinfo.h index 7388356a19..c490561581 100644 --- a/include/sys/sysinfo.h +++ b/include/sys/sysinfo.h @@ -9,10 +9,15 @@ extern int __get_nprocs_conf (void); libc_hidden_proto (__get_nprocs_conf) -/* Return number of available processors. */ +/* Return number of available processors (not all of them will be + available to the caller process). */ extern int __get_nprocs (void); libc_hidden_proto (__get_nprocs) +/* Return the number of available processors which the process can + be scheduled. */ +extern int __get_nprocs_sched (void) attribute_hidden; + /* Return number of physical pages of memory in the system. */ extern long int __get_phys_pages (void); libc_hidden_proto (__get_phys_pages) diff --git a/malloc/arena.c b/malloc/arena.c index 4c398753ae..78ef4cf18c 100644 --- a/malloc/arena.c +++ b/malloc/arena.c @@ -878,7 +878,7 @@ arena_get2 (size_t size, mstate avoid_arena) narenas_limit = mp_.arena_max; else if (narenas > mp_.arena_test) { - int n = __get_nprocs (); + int n = __get_nprocs_sched (); if (n >= 1) narenas_limit = NARENAS_FROM_NCORES (n); diff --git a/misc/getsysstats.c b/misc/getsysstats.c index 2986d62247..5cbba0f9bd 100644 --- a/misc/getsysstats.c +++ b/misc/getsysstats.c @@ -44,6 +44,12 @@ weak_alias (__get_nprocs, get_nprocs) link_warning (get_nprocs, "warning: get_nprocs will always return 1") +int +__get_nprocs_sched (void) +{ + return 1; +} + long int __get_phys_pages (void) { diff --git a/sysdeps/mach/getsysstats.c b/sysdeps/mach/getsysstats.c index 1267f39da2..cc8023f979 100644 --- a/sysdeps/mach/getsysstats.c +++ b/sysdeps/mach/getsysstats.c @@ -62,6 +62,12 @@ __get_nprocs (void) libc_hidden_def (__get_nprocs) weak_alias (__get_nprocs, get_nprocs) +int +__get_nprocs_sched (void) +{ + return __get_nprocs (); +} + /* Return the number of physical pages on the system. */ long int __get_phys_pages (void) diff --git a/sysdeps/unix/sysv/linux/getsysstats.c b/sysdeps/unix/sysv/linux/getsysstats.c index 8a5d342f0c..e9c0dc4d83 100644 --- a/sysdeps/unix/sysv/linux/getsysstats.c +++ b/sysdeps/unix/sysv/linux/getsysstats.c @@ -87,6 +87,12 @@ __get_nprocs (void) libc_hidden_def (__get_nprocs) weak_alias (__get_nprocs, get_nprocs) +int +__get_nprocs_sched (void) +{ + return __get_nprocs (); +} + /* On some architectures it is possible to distinguish between configured and active cpus. */ From patchwork Tue Sep 7 12:22:58 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adhemerval Zanella X-Patchwork-Id: 44883 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 3562C385E448 for ; Tue, 7 Sep 2021 12:24:50 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3562C385E448 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1631017490; bh=b06zMraKWX8WzdRjbQYUxxTb/UDrjGJ1e6pICGIoH3E=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=SLJ96r12JIesGmOze+LhZYKkIATP6JLoGiDAG2NyJwJWQZQq3ZHGhykgI8XIuW0Zi S6axKv4IHknfwp81JiBKM0UNNFjCuAeRRJjs7VLOx6oQHRbBu92m4+pkwHgYK+wB+N 0WJhNJVB2+GrrSoQfdbSYYrUCtO81gDp+Jac4DgM= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-qt1-x836.google.com (mail-qt1-x836.google.com [IPv6:2607:f8b0:4864:20::836]) by sourceware.org (Postfix) with ESMTPS id 13475385842D for ; 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([2804:431:c7cb:733d:f360:5bf3:9813:d8f5]) by smtp.gmail.com with ESMTPSA id r18sm6902148qtm.96.2021.09.07.05.23.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Sep 2021 05:23:05 -0700 (PDT) To: libc-alpha@sourceware.org Subject: [PATCH v2 2/3] linux: Simplify get_nprocs Date: Tue, 7 Sep 2021 09:22:58 -0300 Message-Id: <20210907122259.79800-3-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210907122259.79800-1-adhemerval.zanella@linaro.org> References: <20210907122259.79800-1-adhemerval.zanella@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-12.2 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Adhemerval Zanella via Libc-alpha From: Adhemerval Zanella Reply-To: Adhemerval Zanella Cc: Florian Weimer , Nicolas Saenz Julienne Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" 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 --- posix/Makefile | 3 +- posix/tst-sched_getaffinity.c | 47 ++++++++++++++++++ sysdeps/unix/sysv/linux/getsysstats.c | 68 +++++++-------------------- 3 files changed, 67 insertions(+), 51 deletions(-) create mode 100644 posix/tst-sched_getaffinity.c diff --git a/posix/Makefile b/posix/Makefile index 059efb3cd2..09460a28e8 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 0000000000..6d1fdcb05f --- /dev/null +++ b/posix/tst-sched_getaffinity.c @@ -0,0 +1,47 @@ +/* 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 + . */ + +#include +#include +#include + +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++) + for (int j = 1; j < array_length (cpucount); j++) + TEST_COMPARE (cpucount[i], cpucount[j]); + + return 0; +} + +#include diff --git a/sysdeps/unix/sysv/linux/getsysstats.c b/sysdeps/unix/sysv/linux/getsysstats.c index e9c0dc4d83..1e3d88676d 100644 --- a/sysdeps/unix/sysv/linux/getsysstats.c +++ b/sysdeps/unix/sysv/linux/getsysstats.c @@ -28,61 +28,29 @@ #include #include -/* 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) From patchwork Tue Sep 7 12:22:59 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adhemerval Zanella X-Patchwork-Id: 44884 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 96FC8385E823 for ; Tue, 7 Sep 2021 12:25:32 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 96FC8385E823 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1631017532; bh=zEHpoVo0KK9UfNWAQE99bwIKZBikAJMSSDGIaozFS88=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=B1CVMOi8iTe/qqSAIlHuOpU3701yvSb8MexKLpKVQaDBrNZgoquGN1OfEiLOoMzaw fh6t/x5FTazYBvmry6WvwOy+BHzMMzedjFXloVn6gsrEYJCSQhThZ/tycNUpINzUVj EgrHmeY0N7+QVFERBAMt6URyAwI7Rtm8D7nlK80c= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-qk1-x72a.google.com (mail-qk1-x72a.google.com [IPv6:2607:f8b0:4864:20::72a]) by sourceware.org (Postfix) with ESMTPS id 64FF1385780D for ; Tue, 7 Sep 2021 12:23:07 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 64FF1385780D Received: by mail-qk1-x72a.google.com with SMTP id f22so9821927qkm.5 for ; Tue, 07 Sep 2021 05:23:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=zEHpoVo0KK9UfNWAQE99bwIKZBikAJMSSDGIaozFS88=; b=CFcxYXCkMT0yQ9Lf/iNqPtMlUzU5OVz8TUOhug3jXUoXDo1xJQRG+GXJQI1Qjlbg+X C3sS/5pmO+z8qT+SYVqWMBw2X7YzoHQepUg1POeK6H86vJZwtM9/7ii3Ypef01Q5x2+1 kf6te4uXtB2vmNeZlc1XO+X/cYb/KOhQW4vOYXzznnxjVkciinkLu3Xxgi2sAecfFDhU nkR55tUlh+WRFsuJ7iv8VowiClasUx7+v1ZA63eRxSYge92xKRHRMPvDDfpdV34SWgk3 pqhNogd1Sny8YL8BwZCc694A/9jW83lsM0tFVpKBkOlTipBBWGN2hGzDVzvvFyzGeibE m7rQ== X-Gm-Message-State: AOAM5335WV/Y5q4Z6r7Ckq2dIePVMA47/II/YFuRjPrKYvuiqSxf9qNZ vlYSyhVCa3RL1p3FxiPdSCJzGlW+7UlGGg== X-Google-Smtp-Source: ABdhPJxeBvMODRZd0yvfy+7ciDPJgeUBPWbCky/MmvrzeotQ4l8/6DpPgChb21kH/PXOwXAjhv3CVA== X-Received: by 2002:a37:ea05:: with SMTP id t5mr14920671qkj.515.1631017386844; Tue, 07 Sep 2021 05:23:06 -0700 (PDT) Received: from birita.. ([2804:431:c7cb:733d:f360:5bf3:9813:d8f5]) by smtp.gmail.com with ESMTPSA id r18sm6902148qtm.96.2021.09.07.05.23.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Sep 2021 05:23:06 -0700 (PDT) To: libc-alpha@sourceware.org Subject: [PATCH v2 3/3] linux: Revert the use of sched_getaffinity on get_nproc (BZ #28310) Date: Tue, 7 Sep 2021 09:22:59 -0300 Message-Id: <20210907122259.79800-4-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210907122259.79800-1-adhemerval.zanella@linaro.org> References: <20210907122259.79800-1-adhemerval.zanella@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-12.3 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Adhemerval Zanella via Libc-alpha From: Adhemerval Zanella Reply-To: Adhemerval Zanella Cc: Florian Weimer , Nicolas Saenz Julienne Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" The use of sched_getaffinity on get_nproc and sysconf (_SC_NPROCESSORS_ONLN) done in 903bc7dcc2acafc40 (BZ #27645) breaks the top command in common hypervisor configurations and also other monitoring tools. The main issue using sched_getaffinity changed the symbols semantic from system-wide scope of online CPUs to per-process one (which can be changed with kernel cpusets or book parameters in VM). This patch reverts mostly of the 903bc7dcc2acafc40, with the exceptions: * No more cached values and atomic updates, since they are inherent racy. * No /proc/cpuinfo fallback, since /proc/stat is already used and it would require to revert more arch-specific code. * The alloca is replace with a static buffer of 1024 bytes. So the implementation first consult the sysfs, and fallbacks to procfs. Checked on x86_64-linux-gnu. Reviewed-by: Florian Weimer --- sysdeps/unix/sysv/linux/getsysstats.c | 139 +++++++++++++++++++++++++- 1 file changed, 134 insertions(+), 5 deletions(-) diff --git a/sysdeps/unix/sysv/linux/getsysstats.c b/sysdeps/unix/sysv/linux/getsysstats.c index 1e3d88676d..15ad91cf2f 100644 --- a/sysdeps/unix/sysv/linux/getsysstats.c +++ b/sysdeps/unix/sysv/linux/getsysstats.c @@ -17,6 +17,8 @@ . */ #include +#include +#include #include #include #include @@ -29,7 +31,7 @@ #include int -__get_nprocs (void) +__get_nprocs_sched (void) { enum { @@ -52,14 +54,141 @@ __get_nprocs (void) atomics are needed). */ return 2; } -libc_hidden_def (__get_nprocs) -weak_alias (__get_nprocs, get_nprocs) + +static char * +next_line (int fd, char *const buffer, char **cp, char **re, + char *const buffer_end) +{ + char *res = *cp; + char *nl = memchr (*cp, '\n', *re - *cp); + if (nl == NULL) + { + if (*cp != buffer) + { + if (*re == buffer_end) + { + memmove (buffer, *cp, *re - *cp); + *re = buffer + (*re - *cp); + *cp = buffer; + + ssize_t n = __read_nocancel (fd, *re, buffer_end - *re); + if (n < 0) + return NULL; + + *re += n; + + nl = memchr (*cp, '\n', *re - *cp); + while (nl == NULL && *re == buffer_end) + { + /* Truncate too long lines. */ + *re = buffer + 3 * (buffer_end - buffer) / 4; + n = __read_nocancel (fd, *re, buffer_end - *re); + if (n < 0) + return NULL; + + nl = memchr (*re, '\n', n); + **re = '\n'; + *re += n; + } + } + else + nl = memchr (*cp, '\n', *re - *cp); + + res = *cp; + } + + if (nl == NULL) + nl = *re - 1; + } + + *cp = nl + 1; + assert (*cp <= *re); + + return res == *re ? NULL : res; +} + int -__get_nprocs_sched (void) +__get_nprocs (void) { - return __get_nprocs (); + enum { buffer_size = 1024 }; + char buffer[buffer_size]; + char *buffer_end = buffer + buffer_size; + char *cp = buffer_end; + char *re = buffer_end; + + const int flags = O_RDONLY | O_CLOEXEC; + /* This file contains comma-separated ranges. */ + int fd = __open_nocancel ("/sys/devices/system/cpu/online", flags); + char *l; + int result = 0; + if (fd != -1) + { + l = next_line (fd, buffer, &cp, &re, buffer_end); + if (l != NULL) + do + { + char *endp; + unsigned long int n = strtoul (l, &endp, 10); + if (l == endp) + { + result = 0; + break; + } + + unsigned long int m = n; + if (*endp == '-') + { + l = endp + 1; + m = strtoul (l, &endp, 10); + if (l == endp) + { + result = 0; + break; + } + } + + result += m - n + 1; + + l = endp; + if (l < re && *l == ',') + ++l; + } + while (l < re && *l != '\n'); + + __close_nocancel_nostatus (fd); + + if (result > 0) + return result; + } + + cp = buffer_end; + re = buffer_end; + + /* Default to an SMP system in case we cannot obtain an accurate + number. */ + result = 2; + + fd = __open_nocancel ("/proc/stat", flags); + if (fd != -1) + { + result = 0; + + while ((l = next_line (fd, buffer, &cp, &re, buffer_end)) != NULL) + /* The current format of /proc/stat has all the cpu* entries + at the front. We assume here that stays this way. */ + if (strncmp (l, "cpu", 3) != 0) + break; + else if (isdigit (l[3])) + ++result; + + __close_nocancel_nostatus (fd); + } + + return result; } +libc_hidden_def (__get_nprocs) +weak_alias (__get_nprocs, get_nprocs) /* On some architectures it is possible to distinguish between configured