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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2A161C7EE25 for ; Fri, 9 Jun 2023 08:17:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B40DB8E000C; Fri, 9 Jun 2023 04:17:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id ACCFE8E0003; Fri, 9 Jun 2023 04:17:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 96B298E000C; Fri, 9 Jun 2023 04:17:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 81ECF8E0003 for ; Fri, 9 Jun 2023 04:17:16 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 4CD4E140173 for ; Fri, 9 Jun 2023 08:17:16 +0000 (UTC) X-FDA: 80882504472.27.8E1DE0F Received: from out-33.mta0.migadu.com (out-33.mta0.migadu.com [91.218.175.33]) by imf21.hostedemail.com (Postfix) with ESMTP id 95FAA1C0006 for ; Fri, 9 Jun 2023 08:17:14 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=jXFgIXzL; spf=pass (imf21.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.33 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1686298634; 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=z1jd6DS57tmtOuv1f+tPHUMa7LOeeEWjdKx6Y4gNtNw=; b=GNXSa6G5dXHS9DWtQLwJSSW4yC2yrPZHnvG2fM96ewAd3JH/ZfxCyYcWIeLfA/8NQDUQG9 OSykR3a43KNITyWNiBt52VxAUxJ7xkvyYpKTffvea89/JyS5fBTdf0Q8OjU3BvpB9so28p 4nzWZaaxdn1D/fHDzqsU9/7UUYpPfyI= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=jXFgIXzL; spf=pass (imf21.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.33 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1686298634; a=rsa-sha256; cv=none; b=yAfC0BKdvg0Y88Z5feuoqwbVLRMfFEbJL26PLA/tfsxeLdnkEWd3T5glQo8HFJfmfGY9o9 gXv646ILQ8Jh74iFPTRHGKHjucnsuJm/7tKZZY7tRgW1le68i80w2Dk97OYMb/+F7mfJla ccST9fM+YCHlb4Gc0vVwPjznjaCCg5w= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1686298633; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=z1jd6DS57tmtOuv1f+tPHUMa7LOeeEWjdKx6Y4gNtNw=; b=jXFgIXzLdDJojoKAItNEv34otXyCWjyar4fawUm43LXwyCFBcR8kY9Gpt4WbtUzDcH3jkd /70kJs6ZiU9T/QhpzSJOCDGSO1yj+OA/JWTW7Qjwmfr5MuKM15sXtrYty/nAw5lTGHgi5v rbaXvSWMUUp8lu38yF2ylUnJkp1peeY= From: Qi Zheng To: akpm@linux-foundation.org Cc: david@fromorbit.com, tkhai@ya.ru, roman.gushchin@linux.dev, vbabka@suse.cz, muchun.song@linux.dev, yujie.liu@intel.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Qi Zheng Subject: [PATCH 3/7] Revert "mm: vmscan: hold write lock to reparent shrinker nr_deferred" Date: Fri, 9 Jun 2023 08:15:14 +0000 Message-Id: <20230609081518.3039120-4-qi.zheng@linux.dev> In-Reply-To: <20230609081518.3039120-1-qi.zheng@linux.dev> References: <20230609081518.3039120-1-qi.zheng@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 95FAA1C0006 X-Rspam-User: X-Stat-Signature: jeioyo9ywg1qknium6hgnu9areneehuz X-Rspamd-Server: rspam01 X-HE-Tag: 1686298634-597412 X-HE-Meta: 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 tIwy7aaW 92QUx2idjnbqbAq3VJtlVtZ9j5fGjtmBD9WJJg8YQ3ozlHA/VA2ehaA/bze/mVrXro+iNaJY1UypcMVPy7o2mtmeJo7Q/IcV6mWS9Mpj8qbuZgagQd7BEUPyqrNZNtuUeUovY1SO8whkTwi1ugYhL1iDfv7vFncpQC9cVlo5yPhHkoUba/c8DwlHhBOeL1f2GvLTOspFYl+60uHN19KaipulnKjfgJ/Ux/WpgHREi8IyQbC5pRQ/Q1+u7iXqErb4Cx/9akakoMYtKfSc= 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: From: Qi Zheng This reverts commit b3cabea3c9153fd42fe5cb851ac58b51ea2b32b8. Kernel test robot reports -88.8% regression in stress-ng.ramfs.ops_per_sec test case [1], which is caused by commit f95bdb700bc6 ("mm: vmscan: make global slab shrink lockless"). The root cause is that SRCU has to be careful to not frequently check for SRCU read-side critical section exits. Therefore, even if no one is currently in the SRCU read-side critical section, synchronize_srcu() cannot return quickly. That's why unregister_shrinker() has become slower. We will try to use the refcount+RCU method [2] proposed by Dave Chinner to continue to re-implement the lockless slab shrink. Because there will be other readers after reverting the shrinker_srcu related changes, so it is better to restore to hold read lock to reparent shrinker nr_deferred. [1]. https://lore.kernel.org/lkml/202305230837.db2c233f-yujie.liu@intel.com/ [2]. https://lore.kernel.org/lkml/ZIJhou1d55d4H1s0@dread.disaster.area/ Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202305230837.db2c233f-yujie.liu@intel.com Signed-off-by: Qi Zheng --- mm/vmscan.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 0ba0e1180f3f..d1d309fc3212 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -433,7 +433,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg) parent = root_mem_cgroup; /* Prevent from concurrent shrinker_info expand */ - down_write(&shrinker_rwsem); + down_read(&shrinker_rwsem); for_each_node(nid) { child_info = shrinker_info_protected(memcg, nid); parent_info = shrinker_info_protected(parent, nid); @@ -442,7 +442,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg) atomic_long_add(nr, &parent_info->nr_deferred[i]); } } - up_write(&shrinker_rwsem); + up_read(&shrinker_rwsem); } static bool cgroup_reclaim(struct scan_control *sc) -- 2.30.2