From patchwork Fri Jun 9 08:15:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qi Zheng X-Patchwork-Id: 13273420 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 0639EC83005 for ; Fri, 9 Jun 2023 08:17:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 91D9F8E000F; Fri, 9 Jun 2023 04:17:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8A8058E0003; Fri, 9 Jun 2023 04:17:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 747FA8E000F; Fri, 9 Jun 2023 04:17:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 61C1A8E0003 for ; Fri, 9 Jun 2023 04:17:32 -0400 (EDT) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 3345440173 for ; Fri, 9 Jun 2023 08:17:32 +0000 (UTC) X-FDA: 80882505144.17.8D35FD0 Received: from out-1.mta0.migadu.com (out-1.mta0.migadu.com [91.218.175.1]) by imf22.hostedemail.com (Postfix) with ESMTP id 5B4A4C0015 for ; Fri, 9 Jun 2023 08:17:30 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Hp4UWFqQ; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf22.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.1 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1686298650; 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=B/E+4G7xduNcnh08om90Yauw78sQGFjRZ4mRQx21A2Q=; b=VqijiapVpBPs1ho4J2FBOyhvz3/pezexzZnYcz8o43s4o8MS1AuCDB90McMCB4VhQa0Y+K UuSHpDf3NcKGAEnWeYQgPhwXsd1JzKj74IGzCZ30Pt+0aJ80mUEGjC/Gb4jnUBBMNN5eY0 NW23TdQzlvdpVR1McyYHv0L62UfhBNs= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Hp4UWFqQ; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf22.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.1 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1686298650; a=rsa-sha256; cv=none; b=syiS3x4tckveo6Z+0xWCURu3zrXaoIyfMoxcMbu6SA/sAN7RDX4caa9yfuYKW5w6ATCMd0 bNT1Ukr2T/BtGF2omsQhj6yAWf08QFj2FoyeMMWbVPcBMjpBuz+ltkbwAFigARg/iZ8nT7 Ns7eAZa9ntevd6t2v6wyRK8CaykfclU= 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=1686298649; 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=B/E+4G7xduNcnh08om90Yauw78sQGFjRZ4mRQx21A2Q=; b=Hp4UWFqQJil8Kf9Kbk7PpaCcvuRjBeSALwQccnwRZWKqDBGAxb1HaJdVYPnL+2SqJ79gWL Dvz4OkZmXEAisnQB6TAIkcV1qOdjUk0ksJQqHC9jb/4iwoI78cHfc6hLpTA+6ksOQfKmVx x7esjKuYGnPxyQBoj7U7f+XOMRKIYW8= 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 6/7] Revert "mm: vmscan: make memcg slab shrink lockless" Date: Fri, 9 Jun 2023 08:15:17 +0000 Message-Id: <20230609081518.3039120-7-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: rspam09 X-Rspamd-Queue-Id: 5B4A4C0015 X-Stat-Signature: ktjn5khhax3y6x111mizxzzwjeoozkxw X-Rspam-User: X-HE-Tag: 1686298650-627302 X-HE-Meta: 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 ezptxVLd Z84VzvlJ189Ay9LStKGS9GUvQJyfWtroZajbcBsoaSsCFMrer0xmznPyTYsAejzXyu5oJZ/eCmWvDP536Rfk17KCC0QT1M8rRzlnQ/zmzC1BqLEUlFjkdzLAoxfu7+RAXaEb+5d5epRCsJnJIJhY7oFotXyCISG7WARgqs2iGunHGLf+4tamc89uV9DV6/iKmig54hvu8AOBebbP+l+y5qMkrgODFl2yEfbWb 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 caa05325c9126c77ebf114edce51536a0d0a9a08. 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. After discussion, 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 | 45 +++++++++++++++++++-------------------------- 1 file changed, 19 insertions(+), 26 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 50775b73d0c7..a008d7f2d0fc 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -210,21 +210,8 @@ static inline int shrinker_defer_size(int nr_items) static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg, int nid) { - return srcu_dereference_check(memcg->nodeinfo[nid]->shrinker_info, - &shrinker_srcu, - lockdep_is_held(&shrinker_rwsem)); -} - -static struct shrinker_info *shrinker_info_srcu(struct mem_cgroup *memcg, - int nid) -{ - return srcu_dereference(memcg->nodeinfo[nid]->shrinker_info, - &shrinker_srcu); -} - -static void free_shrinker_info_rcu(struct rcu_head *head) -{ - kvfree(container_of(head, struct shrinker_info, rcu)); + return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info, + lockdep_is_held(&shrinker_rwsem)); } static int expand_one_shrinker_info(struct mem_cgroup *memcg, @@ -265,7 +252,7 @@ static int expand_one_shrinker_info(struct mem_cgroup *memcg, defer_size - old_defer_size); rcu_assign_pointer(pn->shrinker_info, new); - call_srcu(&shrinker_srcu, &old->rcu, free_shrinker_info_rcu); + kvfree_rcu(old, rcu); } return 0; @@ -351,16 +338,15 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) { if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) { struct shrinker_info *info; - int srcu_idx; - srcu_idx = srcu_read_lock(&shrinker_srcu); - info = shrinker_info_srcu(memcg, nid); + rcu_read_lock(); + info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info); if (!WARN_ON_ONCE(shrinker_id >= info->map_nr_max)) { /* Pairs with smp mb in shrink_slab() */ smp_mb__before_atomic(); set_bit(shrinker_id, info->map); } - srcu_read_unlock(&shrinker_srcu, srcu_idx); + rcu_read_unlock(); } } @@ -374,6 +360,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) return -ENOSYS; down_write(&shrinker_rwsem); + /* This may call shrinker, so it must use down_read_trylock() */ id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); if (id < 0) goto unlock; @@ -407,7 +394,7 @@ static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker, { struct shrinker_info *info; - info = shrinker_info_srcu(memcg, nid); + info = shrinker_info_protected(memcg, nid); return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0); } @@ -416,7 +403,7 @@ static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker, { struct shrinker_info *info; - info = shrinker_info_srcu(memcg, nid); + info = shrinker_info_protected(memcg, nid); return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]); } @@ -947,14 +934,15 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, { struct shrinker_info *info; unsigned long ret, freed = 0; - int srcu_idx; int i; if (!mem_cgroup_online(memcg)) return 0; - srcu_idx = srcu_read_lock(&shrinker_srcu); - info = shrinker_info_srcu(memcg, nid); + if (!down_read_trylock(&shrinker_rwsem)) + return 0; + + info = shrinker_info_protected(memcg, nid); if (unlikely(!info)) goto unlock; @@ -1004,9 +992,14 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, set_shrinker_bit(memcg, nid, i); } freed += ret; + + if (rwsem_is_contended(&shrinker_rwsem)) { + freed = freed ? : 1; + break; + } } unlock: - srcu_read_unlock(&shrinker_srcu, srcu_idx); + up_read(&shrinker_rwsem); return freed; } #else /* CONFIG_MEMCG */