From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06F87C43462 for ; Fri, 30 Apr 2021 05:55:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E1D0561463 for ; Fri, 30 Apr 2021 05:55:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229609AbhD3Fz7 (ORCPT ); Fri, 30 Apr 2021 01:55:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:47858 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230132AbhD3Fz6 (ORCPT ); Fri, 30 Apr 2021 01:55:58 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 38ECA61459; Fri, 30 Apr 2021 05:55:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1619762109; bh=fCuDxdluNiOL8XP0etdRnYmP8kbuRgMXotw2TejNmOk=; h=Date:From:To:Subject:In-Reply-To:From; b=007qrzYQVbEdUH0hnRNj2b01VoW53RoCwWbGaM519lgrvf0J1o+io99eILc+06Iwo vEPme5Ep+EFo9vwO2bDCxd7EKeSRtsp9gEMi05qdXhw5WPqb9CNOaAzgvC6H7hwleq oEMbSQvE6jG0TWTdwfktlpvavZjmaNECCqJ7KzM8= Date: Thu, 29 Apr 2021 22:55:08 -0700 From: Andrew Morton To: akpm@linux-foundation.org, bristot@redhat.com, bsegall@google.com, dietmar.eggemann@arm.com, juri.lelli@redhat.com, linux-mm@kvack.org, mgorman@suse.de, mingo@redhat.com, mm-commits@vger.kernel.org, peterz@infradead.org, rostedt@goodmis.org, slyfox@gentoo.org, torvalds@linux-foundation.org, vbabka@suse.cz, vincent.guittot@linaro.org Subject: [patch 038/178] mm: page_owner: detect page_owner recursion via task_struct Message-ID: <20210430055508.Ne8v_ugj7%akpm@linux-foundation.org> In-Reply-To: <20210429225251.02b6386d21b69255b4f6c163@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Sergei Trofimovich Subject: mm: page_owner: detect page_owner recursion via task_struct Before the change page_owner recursion was detected via fetching backtrace and inspecting it for current instruction pointer. It has a few problems: - it is slightly slow as it requires extra backtrace and a linear stack scan of the result - it is too late to check if backtrace fetching required memory allocation itself (ia64's unwinder requires it). To simplify recursion tracking let's use page_owner recursion flag in 'struct task_struct'. The change make page_owner=on work on ia64 by avoiding infinite recursion in: kmalloc() -> __set_page_owner() -> save_stack() -> unwind() [ia64-specific] -> build_script() -> kmalloc() -> __set_page_owner() [we short-circuit here] -> save_stack() -> unwind() [recursion] Link: https://lkml.kernel.org/r/20210402115342.1463781-1-slyfox@gentoo.org Signed-off-by: Sergei Trofimovich Reviewed-by: Andrew Morton Acked-by: Vlastimil Babka Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Steven Rostedt Cc: Ben Segall Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Signed-off-by: Andrew Morton --- include/linux/sched.h | 4 ++++ mm/page_owner.c | 32 ++++++++++---------------------- 2 files changed, 14 insertions(+), 22 deletions(-) --- a/include/linux/sched.h~mm-page_owner-detect-page_owner-recursion-via-task_struct +++ a/include/linux/sched.h @@ -841,6 +841,10 @@ struct task_struct { /* Stalled due to lack of memory */ unsigned in_memstall:1; #endif +#ifdef CONFIG_PAGE_OWNER + /* Used by page_owner=on to detect recursion in page tracking. */ + unsigned in_page_owner:1; +#endif unsigned long atomic_flags; /* Flags requiring atomic access. */ --- a/mm/page_owner.c~mm-page_owner-detect-page_owner-recursion-via-task_struct +++ a/mm/page_owner.c @@ -98,42 +98,30 @@ static inline struct page_owner *get_pag return (void *)page_ext + page_owner_ops.offset; } -static inline bool check_recursive_alloc(unsigned long *entries, - unsigned int nr_entries, - unsigned long ip) -{ - unsigned int i; - - for (i = 0; i < nr_entries; i++) { - if (entries[i] == ip) - return true; - } - return false; -} - static noinline depot_stack_handle_t save_stack(gfp_t flags) { unsigned long entries[PAGE_OWNER_STACK_DEPTH]; depot_stack_handle_t handle; unsigned int nr_entries; - nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2); - /* - * We need to check recursion here because our request to - * stackdepot could trigger memory allocation to save new - * entry. New memory allocation would reach here and call - * stack_depot_save_entries() again if we don't catch it. There is - * still not enough memory in stackdepot so it would try to - * allocate memory again and loop forever. + * Avoid recursion. + * + * Sometimes page metadata allocation tracking requires more + * memory to be allocated: + * - when new stack trace is saved to stack depot + * - when backtrace itself is calculated (ia64) */ - if (check_recursive_alloc(entries, nr_entries, _RET_IP_)) + if (current->in_page_owner) return dummy_handle; + current->in_page_owner = 1; + nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2); handle = stack_depot_save(entries, nr_entries, flags); if (!handle) handle = failure_handle; + current->in_page_owner = 0; return handle; } _