From patchwork Fri Sep 6 05:12:04 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13793243 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6A35C54FC6 for ; Fri, 6 Sep 2024 05:12:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 330686B0085; Fri, 6 Sep 2024 01:12:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2E0DF6B0088; Fri, 6 Sep 2024 01:12:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 15A106B0089; Fri, 6 Sep 2024 01:12:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id EA7F46B0085 for ; Fri, 6 Sep 2024 01:12:21 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 9B0BA140E9F for ; Fri, 6 Sep 2024 05:12:21 +0000 (UTC) X-FDA: 82533142482.07.CD847A4 Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf21.hostedemail.com (Postfix) with ESMTP id 0AED11C0011 for ; Fri, 6 Sep 2024 05:12:19 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=rm0jdEna; spf=pass (imf21.hostedemail.com: domain of andrii@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=andrii@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1725599491; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=bP6R0DkS+tsnHTedFJqfnXzJpWg2HbEuKwvHd0ydJ5A=; b=K/oTEu3TePOJQt3vYHQ5te5p2rPhkWWE0GqAb9Ts1jTfcorPDIF3quhs2GLjGF5ng9AT0o 2jeRfuOWyFxwTT4rXQmvqqrUngsc+ZsWjSRc8EH3/bOslnIb3wZqx+5QNxxTJy85uaoNi9 5gJFLgdaYxu9tO+6LUanpAe3fImyKmc= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=rm0jdEna; spf=pass (imf21.hostedemail.com: domain of andrii@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=andrii@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1725599491; a=rsa-sha256; cv=none; b=uYdlh4eG1WYGCjSf8guM0Xp8PWsFUzZLLPX8DciJiBq4MbHPHXghh6mIXl77DT6ZKraxwL dco7wVetJCtcfbbvrMXQebZ0cnzcCzOMMhv3jlD6jIXZ4lb6Fq2rSvx4shsCdjK4ajx3gF d7+aNn7gEZwoy400TQS3j9dEAgHTtNM= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 04133A4401B; Fri, 6 Sep 2024 05:12:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0516C4CEC8; Fri, 6 Sep 2024 05:12:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1725599538; bh=QeJaV7NxUMr6y7gsUb56bD7q6rDPJGAUdKl0q2s8gUQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rm0jdEnaH3gzrt/ZrzjYJggbJMRhkZ7pVttHT3Y+qQm8rP4KhY2QvSm9MAX8Eu2SE YsrL50oF9CAIz7Br9LxTh4dZT2uhC5roEACDiBZCrIoYMIk+yu7hwLc7AMIH6tFJar GRZ5BwFmqxuwpF6m6qRASY8wfKRHZWJ34QrPHK9cXo3OaHBwJ0urPXPHV4kJACdIBk Nz4szuc7WQA06iXoQBWbbcDWFJm9KnewfJ9cZ1gjWlI0NI+Pif3ioOEsAYa6s1uUy8 nUY5EWljCzZOS9t4CHvTPUDuvvpwtC30A8kEFcc5R3xvBR5SQ3jEUbBfkJYGlwt+MN fwoGEE4m1GKIQ== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, peterz@infradead.org, oleg@redhat.com Cc: rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, willy@infradead.org, surenb@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, mjguzik@gmail.com, brauner@kernel.org, jannh@google.com, Andrii Nakryiko Subject: [PATCH 1/2] mm: introduce mmap_lock_speculation_{start|end} Date: Thu, 5 Sep 2024 22:12:04 -0700 Message-ID: <20240906051205.530219-2-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20240906051205.530219-1-andrii@kernel.org> References: <20240906051205.530219-1-andrii@kernel.org> MIME-Version: 1.0 X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 0AED11C0011 X-Stat-Signature: 4rtufw39ayg8iksb7h5153c9tnrib5ac X-HE-Tag: 1725599539-855173 X-HE-Meta: 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 t7sSn5MU HaXxv2HvuFAAlyX0igspV4LI6mGz0BvGELQ3+DEWFlBWhNEJITQPa/I5JdSJz68yaontTLjPbdQ/blBL2BBo3s86WKY00J4KEAW34Fc1PIifz+ypNnl3Pu5EokDGViHdMgjlPxIxEZKgNpTiwmz5GZvRDyURkeK6hq6TFXlKZbbt3NMaTtsGUmzD1g3GZBRjHswJhTj4fWLLtN5GQb/D+yk9mexHUc753yEhIsFFDS9zwx/EhdaZ6aTab+NsrcgcJ2ymUeVmRu06gO0qVJRQW0AIB+o+G8enwwFRQ/IAd75z8MmMnU9cdsCYLuJ4uv3/kBCLYKkcZzxm2606spk5PRWqflbGRm8xKAR4V7SvdDRKdmPjBoN6h9VKRIEEV5xyxw0OtaNY+z6JPW8E= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Suren Baghdasaryan Add helper functions to speculatively perform operations without read-locking mmap_lock, expecting that mmap_lock will not be write-locked and mm is not modified from under us. A few will-it-scale ([0]) bechmarks were run with and without the changes in this patch on a beefy server. The test script below was used. Most of background activity on the server was stopped, but there could still be some sporadic sources of noise. And frankly, will-it-scale benchmarks themselves aren't 100% noise-free and do fluctuate somewhat. Also malloc1 benchmark was getting stuck for some reason, so it was skipped from benchmarks. But I think it was still useful as a bit of sanity check, but take all of them with a grain of salt. Benchmark script: # cat will_it_scale.sh #!/bin/bash set -eufo pipefail for b in page_fault1 page_fault2 page_fault3 malloc2; do for p in 40; do echo BENCH $b CPU$p $(will-it-scale/${b}_threads -m -t$p -s60 | grep average) done; done; Before (w/o this patch) ======================= BENCH page_fault1 CPU40 average:5403940 BENCH page_fault2 CPU40 average:5019159 BENCH page_fault3 CPU40 average:971057 BENCH malloc2 CPU40 average:1364730680 After (w/ this patch) ===================== BENCH page_fault1 CPU40 average:5485892 BENCH page_fault2 CPU40 average:5047923 BENCH page_fault3 CPU40 average:982953 BENCH malloc2 CPU40 average:1361339890 Results seem to be within the noise of measurements, but perhaps mm folks might have better benchmarks to try. [0] https://github.com/antonblanchard/will-it-scale Suggested-by: Peter Zijlstra Signed-off-by: Suren Baghdasaryan Signed-off-by: Andrii Nakryiko --- include/linux/mm_types.h | 3 +++ include/linux/mmap_lock.h | 53 +++++++++++++++++++++++++++++++-------- kernel/fork.c | 3 --- 3 files changed, 46 insertions(+), 13 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 485424979254..d5e3f907eea4 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -876,6 +876,9 @@ struct mm_struct { * Roughly speaking, incrementing the sequence number is * equivalent to releasing locks on VMAs; reading the sequence * number can be part of taking a read lock on a VMA. + * Incremented every time mmap_lock is write-locked/unlocked. + * Initialized to 0, therefore odd values indicate mmap_lock + * is write-locked and even values that it's released. * * Can be modified under write mmap_lock using RELEASE * semantics. diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index de9dc20b01ba..5410ce741d75 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -71,15 +71,12 @@ static inline void mmap_assert_write_locked(const struct mm_struct *mm) } #ifdef CONFIG_PER_VMA_LOCK -/* - * Drop all currently-held per-VMA locks. - * This is called from the mmap_lock implementation directly before releasing - * a write-locked mmap_lock (or downgrading it to read-locked). - * This should normally NOT be called manually from other places. - * If you want to call this manually anyway, keep in mind that this will release - * *all* VMA write locks, including ones from further up the stack. - */ -static inline void vma_end_write_all(struct mm_struct *mm) +static inline void init_mm_lock_seq(struct mm_struct *mm) +{ + mm->mm_lock_seq = 0; +} + +static inline void inc_mm_lock_seq(struct mm_struct *mm) { mmap_assert_write_locked(mm); /* @@ -91,19 +88,52 @@ static inline void vma_end_write_all(struct mm_struct *mm) */ smp_store_release(&mm->mm_lock_seq, mm->mm_lock_seq + 1); } + +static inline bool mmap_lock_speculation_start(struct mm_struct *mm, int *seq) +{ + /* Pairs with RELEASE semantics in inc_mm_lock_seq(). */ + *seq = smp_load_acquire(&mm->mm_lock_seq); + /* Allow speculation if mmap_lock is not write-locked */ + return (*seq & 1) == 0; +} + +static inline bool mmap_lock_speculation_end(struct mm_struct *mm, int seq) +{ + /* Pairs with RELEASE semantics in inc_mm_lock_seq(). */ + return seq == smp_load_acquire(&mm->mm_lock_seq); +} + #else -static inline void vma_end_write_all(struct mm_struct *mm) {} +static inline void init_mm_lock_seq(struct mm_struct *mm) {} +static inline void inc_mm_lock_seq(struct mm_struct *mm) {} +static inline bool mmap_lock_speculation_start(struct mm_struct *mm, int *seq) { return false; } +static inline bool mmap_lock_speculation_end(struct mm_struct *mm, int seq) { return false; } #endif +/* + * Drop all currently-held per-VMA locks. + * This is called from the mmap_lock implementation directly before releasing + * a write-locked mmap_lock (or downgrading it to read-locked). + * This should normally NOT be called manually from other places. + * If you want to call this manually anyway, keep in mind that this will release + * *all* VMA write locks, including ones from further up the stack. + */ +static inline void vma_end_write_all(struct mm_struct *mm) +{ + inc_mm_lock_seq(mm); +} + static inline void mmap_init_lock(struct mm_struct *mm) { init_rwsem(&mm->mmap_lock); + init_mm_lock_seq(mm); } static inline void mmap_write_lock(struct mm_struct *mm) { __mmap_lock_trace_start_locking(mm, true); down_write(&mm->mmap_lock); + inc_mm_lock_seq(mm); __mmap_lock_trace_acquire_returned(mm, true, true); } @@ -111,6 +141,7 @@ static inline void mmap_write_lock_nested(struct mm_struct *mm, int subclass) { __mmap_lock_trace_start_locking(mm, true); down_write_nested(&mm->mmap_lock, subclass); + inc_mm_lock_seq(mm); __mmap_lock_trace_acquire_returned(mm, true, true); } @@ -120,6 +151,8 @@ static inline int mmap_write_lock_killable(struct mm_struct *mm) __mmap_lock_trace_start_locking(mm, true); ret = down_write_killable(&mm->mmap_lock); + if (!ret) + inc_mm_lock_seq(mm); __mmap_lock_trace_acquire_returned(mm, true, ret == 0); return ret; } diff --git a/kernel/fork.c b/kernel/fork.c index 18bdc87209d0..c44b71d354ee 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1259,9 +1259,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, seqcount_init(&mm->write_protect_seq); mmap_init_lock(mm); INIT_LIST_HEAD(&mm->mmlist); -#ifdef CONFIG_PER_VMA_LOCK - mm->mm_lock_seq = 0; -#endif mm_pgtables_bytes_init(mm); mm->map_count = 0; mm->locked_vm = 0;