From patchwork Fri Jun 9 08:15:16 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qi Zheng X-Patchwork-Id: 13273419 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 3B5D6C7EE2E for ; Fri, 9 Jun 2023 08:17:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CA21C8E000E; Fri, 9 Jun 2023 04:17:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C2A848E0003; Fri, 9 Jun 2023 04:17:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ACB208E000E; Fri, 9 Jun 2023 04:17:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 98CA28E0003 for ; Fri, 9 Jun 2023 04:17:28 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 70331AE67A for ; Fri, 9 Jun 2023 08:17:28 +0000 (UTC) X-FDA: 80882504976.11.7F0117A Received: from out-33.mta0.migadu.com (out-33.mta0.migadu.com [91.218.175.33]) by imf05.hostedemail.com (Postfix) with ESMTP id A369C100011 for ; Fri, 9 Jun 2023 08:17:26 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=dUWb27UU; spf=pass (imf05.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=1686298646; a=rsa-sha256; cv=none; b=ayDpNUkPc/8OIsZSn+z+8BlQhXaWMwsobjxt2NyKhsieLG9vbpQgd0KuD9/1RRmjhEwgT0 ywp44iz+9i2MkqYfCFEaIET8STPAezev3OoxchrzIGdgfLXA2ONf9euxStI97kyQxonbVZ rUVkmx5Bbj0XxnS50xXd9sqwWpMpcuA= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=dUWb27UU; spf=pass (imf05.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=1686298646; 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=ptGmpfMk/kHVim/COA1N68hD8MGHSDZD7U0gMdC3pxY=; b=q1CRHfAlqbhEDqFQAuygHB7CqdF3DPIkQUWH5ej2/geJsSVRnQSSFRcM/oI2WzhlBQOFc6 sinImrAVXZ0lAz8xxienyyxLr8SbkrT3vLQKH4M/YYWNxieQ52+z9t4Ib28yXOwCrJyilo OoqBAd1sP09U7zRUM+aKJbe0ws2Plx0= 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=1686298645; 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=ptGmpfMk/kHVim/COA1N68hD8MGHSDZD7U0gMdC3pxY=; b=dUWb27UUXt+8QDbQIc9tustr3Ex0BabLxTJee5D+fXjeHZBQ4qcFjuXfmS9deSWg9pnPCR 9dTR+kP4JvZRsxWTBrikjSS0f2Fm0CUyHJiy5VG+bhRcgClpEyEjDlHhnKlTs1O4PWyCUu 6wpdq+dene7opH5wdk+agSCOHXRmYcg= 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 5/7] Revert "mm: vmscan: add shrinker_srcu_generation" Date: Fri, 9 Jun 2023 08:15:16 +0000 Message-Id: <20230609081518.3039120-6-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 X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A369C100011 X-Stat-Signature: mq8cthua1f7q7opck9tr7o65jwpjmmuu X-Rspam-User: X-HE-Tag: 1686298646-312968 X-HE-Meta: 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 hvnLM9z2 a95BdboFbD+9iEm+A2dkj3XOgpoinBikyIKAuwraKYUm4BipqHAJB/xPHaUH9/h7HG7zgwPg7VN8b/bL5sZcP5Y6BDpf5b8gEG9QelesXtxAwib8UkK+0z2w2JHlhKCZ6f6Z/GAEmHkCIRrM+gvUvuGBjgcNHOv4ThJzm1hE0Q1ng16qwxv9Fw5pSfNkDCFmqJ8clkP1pmjHzVG0aHKO3ysc5VwKClfYIhkO12SL5cFICmc9iJmuhzmka8eyDcZnphtB02eLSCnJggKg= 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 475733dda5aedba9e086379aafe6b5ffd53e8f5e. 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. So revert the shrinker_srcu related changes first. [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 | 24 ++++-------------------- 1 file changed, 4 insertions(+), 20 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index d1d309fc3212..50775b73d0c7 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -192,7 +192,6 @@ int vm_swappiness = 60; LIST_HEAD(shrinker_list); DECLARE_RWSEM(shrinker_rwsem); DEFINE_SRCU(shrinker_srcu); -static atomic_t shrinker_srcu_generation = ATOMIC_INIT(0); #ifdef CONFIG_MEMCG static int shrinker_nr_max; @@ -818,7 +817,6 @@ void unregister_shrinker(struct shrinker *shrinker) debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id); up_write(&shrinker_rwsem); - atomic_inc(&shrinker_srcu_generation); synchronize_srcu(&shrinker_srcu); shrinker_debugfs_remove(debugfs_entry, debugfs_id); @@ -840,7 +838,6 @@ void synchronize_shrinkers(void) { down_write(&shrinker_rwsem); up_write(&shrinker_rwsem); - atomic_inc(&shrinker_srcu_generation); synchronize_srcu(&shrinker_srcu); } EXPORT_SYMBOL(synchronize_shrinkers); @@ -950,20 +947,18 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, { struct shrinker_info *info; unsigned long ret, freed = 0; - int srcu_idx, generation; - int i = 0; + int srcu_idx; + int i; if (!mem_cgroup_online(memcg)) return 0; -again: srcu_idx = srcu_read_lock(&shrinker_srcu); info = shrinker_info_srcu(memcg, nid); if (unlikely(!info)) goto unlock; - generation = atomic_read(&shrinker_srcu_generation); - for_each_set_bit_from(i, info->map, info->map_nr_max) { + for_each_set_bit(i, info->map, info->map_nr_max) { struct shrink_control sc = { .gfp_mask = gfp_mask, .nid = nid, @@ -1009,11 +1004,6 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, set_shrinker_bit(memcg, nid, i); } freed += ret; - if (atomic_read(&shrinker_srcu_generation) != generation) { - srcu_read_unlock(&shrinker_srcu, srcu_idx); - i++; - goto again; - } } unlock: srcu_read_unlock(&shrinker_srcu, srcu_idx); @@ -1053,7 +1043,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, { unsigned long ret, freed = 0; struct shrinker *shrinker; - int srcu_idx, generation; + int srcu_idx; /* * The root memcg might be allocated even though memcg is disabled @@ -1067,7 +1057,6 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, srcu_idx = srcu_read_lock(&shrinker_srcu); - generation = atomic_read(&shrinker_srcu_generation); list_for_each_entry_srcu(shrinker, &shrinker_list, list, srcu_read_lock_held(&shrinker_srcu)) { struct shrink_control sc = { @@ -1080,11 +1069,6 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, if (ret == SHRINK_EMPTY) ret = 0; freed += ret; - - if (atomic_read(&shrinker_srcu_generation) != generation) { - freed = freed ? : 1; - break; - } } srcu_read_unlock(&shrinker_srcu, srcu_idx);