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 AEFF3C19F20 for ; Tue, 2 May 2023 21:56:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229482AbjEBV40 (ORCPT ); Tue, 2 May 2023 17:56:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41900 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229461AbjEBV4X (ORCPT ); Tue, 2 May 2023 17:56:23 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8DB2B1704 for ; Tue, 2 May 2023 14:56:22 -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 2A02761E7D for ; Tue, 2 May 2023 21:56:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84B5AC433D2; Tue, 2 May 2023 21:56:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1683064581; bh=EfFmWR0aF+ebRVwzivj0NT1KtblR0UT1BbGrQlQu9+U=; h=Date:To:From:Subject:From; b=RKt0nNbuacO6SethvthfmUdZPTQ2ZKOTCxBDuL7BLkg5G1/znYXLthOoef54sikif gPuQ2ZAItxYPRNDAq1gU4nw/X7A5GizMXBGhLsqYQZqQtV/urwoy6pXr0LunhlmL/b 4rWnarwhd/E3H3V3R2+v9Kklr0sSPRx+MvhQXQSU= Date: Tue, 02 May 2023 14:56:20 -0700 To: mm-commits@vger.kernel.org, shakeelb@google.com, roman.gushchin@linux.dev, mhocko@suse.com, hannes@cmpxchg.org, haifeng.xu@shopee.com, akpm@linux-foundation.org From: Andrew Morton Subject: + memcg-oom-remove-explicit-wakeup-in-mem_cgroup_oom_synchronize.patch added to mm-unstable branch Message-Id: <20230502215621.84B5AC433D2@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: memcg, oom: remove explicit wakeup in mem_cgroup_oom_synchronize() has been added to the -mm mm-unstable branch. Its filename is memcg-oom-remove-explicit-wakeup-in-mem_cgroup_oom_synchronize.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcg-oom-remove-explicit-wakeup-in-mem_cgroup_oom_synchronize.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Haifeng Xu Subject: memcg, oom: remove explicit wakeup in mem_cgroup_oom_synchronize() Date: Wed, 19 Apr 2023 03:07:39 +0000 Before commit 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the charge path"), all memcg oom killers were delayed to page fault path. And the explicit wakeup is used in this case: thread A: ... if (locked) { // complete oom-kill, hold the lock mem_cgroup_oom_unlock(memcg); ... } ... thread B: ... if (locked && !memcg->oom_kill_disable) { ... } else { schedule(); // can't acquire the lock ... } ... The reason is that thread A kicks off the OOM-killer, which leads to wakeups from the uncharges of the exiting task. But thread B is not guaranteed to see them if it enters the OOM path after the OOM kills but before thread A releases the lock. Now only oom_kill_disable case is handled from the #PF path. In that case it is userspace to trigger the wake up not the #PF path itself. All potential paths to free some charges are responsible to call memcg_oom_recover() , so the explicit wakeup is not needed in the mem_cgroup_oom_synchronize() path which doesn't release any memory itself. Link: https://lkml.kernel.org/r/20230419030739.115845-2-haifeng.xu@shopee.com Signed-off-by: Haifeng Xu Suggested-by: Michal Hocko Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Roman Gushchin Cc: Shakeel Butt Signed-off-by: Andrew Morton --- mm/memcontrol.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) --- a/mm/memcontrol.c~memcg-oom-remove-explicit-wakeup-in-mem_cgroup_oom_synchronize +++ a/mm/memcontrol.c @@ -2028,15 +2028,8 @@ bool mem_cgroup_oom_synchronize(bool han mem_cgroup_unmark_under_oom(memcg); finish_wait(&memcg_oom_waitq, &owait.wait); - if (locked) { + if (locked) mem_cgroup_oom_unlock(memcg); - /* - * There is no guarantee that an OOM-lock contender - * sees the wakeups triggered by the OOM kill - * uncharges. Wake any sleepers explicitly. - */ - memcg_oom_recover(memcg); - } cleanup: current->memcg_in_oom = NULL; css_put(&memcg->css); _ Patches currently in -mm which might be from haifeng.xu@shopee.com are cpuset-clean-up-cpuset_node_allowed.patch memcg-oom-remove-unnecessary-check-in-mem_cgroup_oom_synchronize.patch memcg-oom-remove-explicit-wakeup-in-mem_cgroup_oom_synchronize.patch