From patchwork Fri Jun 9 08:15:15 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qi Zheng X-Patchwork-Id: 13273418 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 7A3F6C7EE2E for ; Fri, 9 Jun 2023 08:17:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 092958E000D; Fri, 9 Jun 2023 04:17:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 01C158E0003; Fri, 9 Jun 2023 04:17:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DFF058E000D; Fri, 9 Jun 2023 04:17:21 -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 CDC268E0003 for ; Fri, 9 Jun 2023 04:17:21 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 9CECEA0147 for ; Fri, 9 Jun 2023 08:17:21 +0000 (UTC) X-FDA: 80882504682.21.0F3E2CC Received: from out-13.mta0.migadu.com (out-13.mta0.migadu.com [91.218.175.13]) by imf06.hostedemail.com (Postfix) with ESMTP id C6733180005 for ; Fri, 9 Jun 2023 08:17:19 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=tddMOX9h; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf06.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.13 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=1686298640; 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=fW5UuGuy06FRX8Px/N9YG/QTNF0coGlqdNSj4AuBaaM=; b=Hg2YXWSmoFWaxrjVrrB0VQJny2k+PBPUv2ak6n8K2W5kEwiw4Fnj14pNqPXCxQl9E2qiJw 6QXKX4SDDCvhy5gSYVy+WtcSXgI3db1hjy+tsBAUzkvbXEfHc2s8516qbk5ykyonqqNLDq G5Xieoncdrn8MqkU57VT4pbrzeyoKwY= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=tddMOX9h; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf06.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.13 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1686298640; a=rsa-sha256; cv=none; b=dpf9CQvfJAZe6mfG9nDngb6s+W/LTfbbuXN1xyWqiq47C2301lMxVQGqYNvZi94DYO4jAb WC1kwwOIT569Do3/IXKsfIDUpLvEIRMeVytXXR2lpRzZOx5JwzlUu+wYqXlKFkXsyTH9lR WJxK7D00bgt4xJXsXep1UysuvPo58Xo= 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=1686298638; 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=fW5UuGuy06FRX8Px/N9YG/QTNF0coGlqdNSj4AuBaaM=; b=tddMOX9hrmBcUy1TaN6PYmjZr8N6htWv1AKIwBbCiMwwdMPB0GeJMYgG8Z8I93aOe/HBvd 5BXFnyv6bfT5hursOmsbSE208IL5wiQKL+bwZlti5+T99GzbUZ4tm7iuHx6iPsFe8QHCGt jtNfOoIRqSFtiW109WCZ6dTaNr7m36M= 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 4/7] Revert "mm: shrinkers: make count and scan in shrinker debugfs lockless" Date: Fri, 9 Jun 2023 08:15:15 +0000 Message-Id: <20230609081518.3039120-5-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-Queue-Id: C6733180005 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 36dg36no37mjtsw8br36uziu6ruzy9bx X-HE-Tag: 1686298639-478269 X-HE-Meta: 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 BMC3+xTy tGWkRZKGytwS64N8TjpZXr32KlsOpUpF+i4MBbWBUyayEPFunaQNT2tmuVPxLjPl4HlJmhSXAdKXtLUGmICcmwRcp4jelpt3L05gNPx+oI1B9px6Ofl1ymzuiGIm3bhxSm9C6DWEa/7vcm8aR1L1eJubzhifLGYpAe5p/WLPfX+KJanPjG1K3qsNYUMqvLkwsrj4rif7+3IQ+eBc67xGY77CYxzfDpZT5dU3i 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 20cd1892fcc3efc10a7ac327cc3790494bec46b5. 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/shrinker_debug.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c index 2be15b8a6d0b..3ab53fad8876 100644 --- a/mm/shrinker_debug.c +++ b/mm/shrinker_debug.c @@ -5,12 +5,10 @@ #include #include #include -#include /* defined in vmscan.c */ extern struct rw_semaphore shrinker_rwsem; extern struct list_head shrinker_list; -extern struct srcu_struct shrinker_srcu; static DEFINE_IDA(shrinker_debugfs_ida); static struct dentry *shrinker_debugfs_root; @@ -51,13 +49,18 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v) struct mem_cgroup *memcg; unsigned long total; bool memcg_aware; - int ret = 0, nid, srcu_idx; + int ret, nid; count_per_node = kcalloc(nr_node_ids, sizeof(unsigned long), GFP_KERNEL); if (!count_per_node) return -ENOMEM; - srcu_idx = srcu_read_lock(&shrinker_srcu); + ret = down_read_killable(&shrinker_rwsem); + if (ret) { + kfree(count_per_node); + return ret; + } + rcu_read_lock(); memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE; @@ -88,7 +91,8 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v) } } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); - srcu_read_unlock(&shrinker_srcu, srcu_idx); + rcu_read_unlock(); + up_read(&shrinker_rwsem); kfree(count_per_node); return ret; @@ -111,8 +115,9 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file, .gfp_mask = GFP_KERNEL, }; struct mem_cgroup *memcg = NULL; - int nid, srcu_idx; + int nid; char kbuf[72]; + ssize_t ret; read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1); if (copy_from_user(kbuf, buf, read_len)) @@ -141,7 +146,11 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file, return -EINVAL; } - srcu_idx = srcu_read_lock(&shrinker_srcu); + ret = down_read_killable(&shrinker_rwsem); + if (ret) { + mem_cgroup_put(memcg); + return ret; + } sc.nid = nid; sc.memcg = memcg; @@ -150,7 +159,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file, shrinker->scan_objects(shrinker, &sc); - srcu_read_unlock(&shrinker_srcu, srcu_idx); + up_read(&shrinker_rwsem); mem_cgroup_put(memcg); return size;