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 9D84BEB64DA for ; Mon, 19 Jun 2023 20:20:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230084AbjFSUUn (ORCPT ); Mon, 19 Jun 2023 16:20:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229530AbjFSUUV (ORCPT ); Mon, 19 Jun 2023 16:20:21 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A243010C2 for ; Mon, 19 Jun 2023 13:20:19 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 365BB60E71 for ; Mon, 19 Jun 2023 20:20:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92652C433C0; Mon, 19 Jun 2023 20:20:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1687206018; bh=yfQdtfCJImUG389W9IZc+MJiyHV4JBQUEM3RJRubmLU=; h=Date:To:From:Subject:From; b=bWcLsZRCB2Ppvx+JubXo2/iFeeup8ha96Jx3KOTNie/SrHj97gKGyvK6pdFboPE1Y bJST+wBiN9JAU0UgPpSlOZ2Wd9O+cJaIDPZzBhDiNITayRt9/p8c1lSiieWquNTjTS nkytsVB4Fo8bt7KHkyKG4VzN0DQk+tXrgN7Bu15I= Date: Mon, 19 Jun 2023 13:20:18 -0700 To: mm-commits@vger.kernel.org, yujie.liu@intel.com, vbabka@suse.cz, tkhai@ya.ru, roman.gushchin@linux.dev, muchun.song@linux.dev, david@fromorbit.com, zhengqi.arch@bytedance.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] revert-mm-shrinkers-make-count-and-scan-in-shrinker-debugfs-lockless.patch removed from -mm tree Message-Id: <20230619202018.92652C433C0@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The quilt patch titled Subject: Revert "mm: shrinkers: make count and scan in shrinker debugfs lockless" has been removed from the -mm tree. Its filename was revert-mm-shrinkers-make-count-and-scan-in-shrinker-debugfs-lockless.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Qi Zheng Subject: Revert "mm: shrinkers: make count and scan in shrinker debugfs lockless" Date: Fri, 9 Jun 2023 08:15:15 +0000 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/ Link: https://lkml.kernel.org/r/20230609081518.3039120-5-qi.zheng@linux.dev Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202305230837.db2c233f-yujie.liu@intel.com Signed-off-by: Qi Zheng Cc: Dave Chinner Cc: Kirill Tkhai Cc: Muchun Song Cc: Roman Gushchin Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/shrinker_debug.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) --- a/mm/shrinker_debug.c~revert-mm-shrinkers-make-count-and-scan-in-shrinker-debugfs-lockless +++ a/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(s 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(s } } 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_wri .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_wri 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_wri shrinker->scan_objects(shrinker, &sc); - srcu_read_unlock(&shrinker_srcu, srcu_idx); + up_read(&shrinker_rwsem); mem_cgroup_put(memcg); return size; _ Patches currently in -mm which might be from zhengqi.arch@bytedance.com are