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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C054EC433FE for ; Fri, 25 Mar 2022 22:41:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233899AbiCYWnP (ORCPT ); Fri, 25 Mar 2022 18:43:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233901AbiCYWnJ (ORCPT ); Fri, 25 Mar 2022 18:43:09 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61BDF208C1E for ; Fri, 25 Mar 2022 15:41:33 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id F21F2614BD for ; Fri, 25 Mar 2022 22:41:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53C32C340ED; Fri, 25 Mar 2022 22:41:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1648248092; bh=SIhQ/QF4q1KnvEg3+sKrYvYXbRsNUR4nzdubndfoGC0=; h=Date:To:From:Subject:From; b=h+/PD+E/16y0flrTeHUursancrD0OI5JH5iPISaakf5cIQBjhPXOwiZX9CaWEKA0X cL8OsfoZoXNyxcKBbFOWxIxEOi8B0PXeUpRDm6a1BiQswqMYqI6oG8UZyzoF7bgQ+q mXnVEIWUr1JTm8rgDUvsVeoIyNglCvwAMJ0NPyys= Date: Fri, 25 Mar 2022 15:41:31 -0700 To: mm-commits@vger.kernel.org, vdavydov.dev@gmail.com, senozhatsky@chromium.org, rppt@linux.ibm.com, rostedt@goodmis.org, roman.gushchin@linux.dev, rientjes@google.com, pmladek@suse.com, mhocko@kernel.org, linux@rasmusvillemoes.dk, ira.weiny@intel.com, hannes@cmpxchg.org, guro@fb.com, aquini@redhat.com, andriy.shevchenko@linux.intel.com, longman@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged] lib-vsprintf-avoid-redundant-work-with-0-size.patch removed from -mm tree Message-Id: <20220325224132.53C32C340ED@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: lib/vsprintf: avoid redundant work with 0 size has been removed from the -mm tree. Its filename was lib-vsprintf-avoid-redundant-work-with-0-size.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Waiman Long Subject: lib/vsprintf: avoid redundant work with 0 size Patch series "mm/page_owner: Extend page_owner to show memcg information", v4. While debugging the constant increase in percpu memory consumption on a system that spawned large number of containers, it was found that a lot of offline mem_cgroup structures remained in place without being freed. Further investigation indicated that those mem_cgroup structures were pinned by some pages. In order to find out what those pages are, the existing page_owner debugging tool is extended to show memory cgroup information and whether those memcgs are offline or not. With the enhanced page_owner tool, the following is a typical page that pinned the mem_cgroup structure in my test case: Page allocated via order 0, mask 0x1100cca(GFP_HIGHUSER_MOVABLE), pid 162970 (podman), ts 1097761405537 ns, free_ts 1097760838089 ns PFN 1925700 type Movable Block 3761 type Movable Flags 0x17ffffc00c001c(uptodate|dirty|lru|reclaim|swapbacked|node=0|zone=2|lastcpupid=0x1fffff) prep_new_page+0xac/0xe0 get_page_from_freelist+0x1327/0x14d0 __alloc_pages+0x191/0x340 alloc_pages_vma+0x84/0x250 shmem_alloc_page+0x3f/0x90 shmem_alloc_and_acct_page+0x76/0x1c0 shmem_getpage_gfp+0x281/0x940 shmem_write_begin+0x36/0xe0 generic_perform_write+0xed/0x1d0 __generic_file_write_iter+0xdc/0x1b0 generic_file_write_iter+0x5d/0xb0 new_sync_write+0x11f/0x1b0 vfs_write+0x1ba/0x2a0 ksys_write+0x59/0xd0 do_syscall_64+0x37/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae Charged to offline memcg libpod-conmon-15e4f9c758422306b73b2dd99f9d50a5ea53cbb16b4a13a2c2308a4253cc0ec8. So the page was not freed because it was part of a shmem segment. That is useful information that can help users to diagnose similar problems. With cgroup v1, /proc/cgroups can be read to find out the total number of memory cgroups (online + offline). With cgroup v2, the cgroup.stat of the root cgroup can be read to find the number of dying cgroups (most likely pinned by dying memcgs). The page_owner feature is not supposed to be enabled for production system due to its memory overhead. However, if it is suspected that dying memcgs are increasing over time, a test environment with page_owner enabled can then be set up with appropriate workload for further analysis on what may be causing the increasing number of dying memcgs. This patch (of 4): For *scnprintf(), vsnprintf() is always called even if the input size is 0. That is a waste of time, so just return 0 in this case. Note that vsnprintf() will never return -1 to indicate an error. So skipping the call to vsnprintf() when size is 0 will have no functional impact at all. Link: https://lkml.kernel.org/r/20220202203036.744010-1-longman@redhat.com Link: https://lkml.kernel.org/r/20220202203036.744010-2-longman@redhat.com Signed-off-by: Waiman Long Acked-by: David Rientjes Reviewed-by: Sergey Senozhatsky Acked-by: Roman Gushchin Acked-by: Rafael Aquini Acked-by: Mike Rapoport Cc: Roman Gushchin Cc: Johannes Weiner Cc: Michal Hocko Cc: Vladimir Davydov Cc: Petr Mladek Cc: Steven Rostedt (Google) Cc: Andy Shevchenko Cc: Rasmus Villemoes Cc: Ira Weiny Cc: David Rientjes Signed-off-by: Andrew Morton --- lib/vsprintf.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/lib/vsprintf.c~lib-vsprintf-avoid-redundant-work-with-0-size +++ a/lib/vsprintf.c @@ -2906,13 +2906,15 @@ int vscnprintf(char *buf, size_t size, c { int i; + if (unlikely(!size)) + return 0; + i = vsnprintf(buf, size, fmt, args); if (likely(i < size)) return i; - if (size != 0) - return size - 1; - return 0; + + return size - 1; } EXPORT_SYMBOL(vscnprintf); _ Patches currently in -mm which might be from longman@redhat.com are ipc-mqueue-use-get_tree_nodev-in-mqueue_get_tree.patch