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 X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 115D0C433E0 for ; Mon, 8 Mar 2021 21:12:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D758C64F9C for ; Mon, 8 Mar 2021 21:12:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231263AbhCHVLk (ORCPT ); Mon, 8 Mar 2021 16:11:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60074 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231335AbhCHVLS (ORCPT ); Mon, 8 Mar 2021 16:11:18 -0500 Received: from mail-lj1-x233.google.com (mail-lj1-x233.google.com [IPv6:2a00:1450:4864:20::233]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3EE74C06174A for ; Mon, 8 Mar 2021 13:11:18 -0800 (PST) Received: by mail-lj1-x233.google.com with SMTP id r25so17885447ljk.11 for ; Mon, 08 Mar 2021 13:11:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=fheXQogWNqXPedd/D/bL/IATUJjbirprHsz26R2GGZc=; b=bofYdG2VMHC5QgtWzMDbTmAePkLxuPsokECM19WVof+iphMqmzd7vSq9HGjIDrh4pf tbh+j2rva0fKinU4VXkRHMzlgGGQIiQWLfCXvftrZcXXBKeejE7t9zkGDXJb7uacgNc4 kon4geP0ZOWvx6i3kexK9MJt4qeXlizwYFlWhXzM/q39yj3vjofPQUR4Zth//ZxUE+Jm 6/8VVW+wzjGEOHPrc5h87oFcsdixpA+3ugVP6bJ7PFUo0ayLXGdMGhfkQt3AzjHCOTBN 9clEM0QC/SOvF9avCw71YPcEPIToO9tR1sihtPwkn4ndQBrse85HYp3tVHMarqkovLme O4ig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=fheXQogWNqXPedd/D/bL/IATUJjbirprHsz26R2GGZc=; b=Qc7ZY7429of2dOV4pHofHJhw1nPuTcHvSjUDVGkwYYJYbNrUpUHmL+MgjYgQycRHRE +BP3Q19tkAybDirJeQrEGDwFk7yeL9eKXyCg4hSFUM3eajWyYhUQKdF9D1s6KfUDg3cN uEY4+HoGxdNH2rfKbg+jPb2djxbrxZm1P74EYyCjAOLh54oxBcXm67usBzfnb9c44eE7 ahquAItpvi3cFNjmniLOsQwZqhVlLiIyzVf161+cn09Z/PO/oq6dxpJ2S/UtlWfaGtaR 9pXKVUjf25EXq6gehPXt8oHW3jmTYNJfCKe0xAm49Gk1pi7YzvWRlL8iwUBZjQGDDIVL A4kg== X-Gm-Message-State: AOAM530H9W05L8iXS4vjFmRcPB1RO4u3cB3WdS7CbdecSrKZ6CUVvy25 Thdl11WN1/kewaE6ymvP26/eCAKZ+Hcd3MbROGsnoA== X-Google-Smtp-Source: ABdhPJxDGJH4/+aRGbwOly/sxB5w5c7gW/5b29K8HWw/hVALIBWRe3U68uFXKXg7WZjziaM8XTiS0NtNerqCf0FklDM= X-Received: by 2002:a2e:7d03:: with SMTP id y3mr15321965ljc.0.1615237876494; Mon, 08 Mar 2021 13:11:16 -0800 (PST) MIME-Version: 1.0 References: <20210217001322.2226796-1-shy828301@gmail.com> <20210217001322.2226796-10-shy828301@gmail.com> In-Reply-To: From: Shakeel Butt Date: Mon, 8 Mar 2021 13:11:02 -0800 Message-ID: Subject: Re: [v8 PATCH 09/13] mm: vmscan: add per memcg shrinker nr_deferred To: Yang Shi Cc: Roman Gushchin , Kirill Tkhai , Vlastimil Babka , Dave Chinner , Johannes Weiner , Michal Hocko , Andrew Morton , Linux MM , linux-fsdevel , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 8, 2021 at 12:30 PM Yang Shi wrote: > > On Mon, Mar 8, 2021 at 11:12 AM Shakeel Butt wrote: > > > > On Tue, Feb 16, 2021 at 4:13 PM Yang Shi wrote: > > > > > > Currently the number of deferred objects are per shrinker, but some slabs, for example, > > > vfs inode/dentry cache are per memcg, this would result in poor isolation among memcgs. > > > > > > The deferred objects typically are generated by __GFP_NOFS allocations, one memcg with > > > excessive __GFP_NOFS allocations may blow up deferred objects, then other innocent memcgs > > > may suffer from over shrink, excessive reclaim latency, etc. > > > > > > For example, two workloads run in memcgA and memcgB respectively, workload in B is vfs > > > heavy workload. Workload in A generates excessive deferred objects, then B's vfs cache > > > might be hit heavily (drop half of caches) by B's limit reclaim or global reclaim. > > > > > > We observed this hit in our production environment which was running vfs heavy workload > > > shown as the below tracing log: > > > > > > <...>-409454 [016] .... 28286961.747146: mm_shrink_slab_start: super_cache_scan+0x0/0x1a0 ffff9a83046f3458: > > > nid: 1 objects to shrink 3641681686040 gfp_flags GFP_HIGHUSER_MOVABLE|__GFP_ZERO pgs_scanned 1 lru_pgs 15721 > > > cache items 246404277 delta 31345 total_scan 123202138 > > > <...>-409454 [022] .... 28287105.928018: mm_shrink_slab_end: super_cache_scan+0x0/0x1a0 ffff9a83046f3458: > > > nid: 1 unused scan count 3641681686040 new scan count 3641798379189 total_scan 602 > > > last shrinker return val 123186855 > > > > > > The vfs cache and page cache ratio was 10:1 on this machine, and half of caches were dropped. > > > This also resulted in significant amount of page caches were dropped due to inodes eviction. > > > > > > Make nr_deferred per memcg for memcg aware shrinkers would solve the unfairness and bring > > > better isolation. > > > > > > When memcg is not enabled (!CONFIG_MEMCG or memcg disabled), the shrinker's nr_deferred > > > would be used. And non memcg aware shrinkers use shrinker's nr_deferred all the time. > > > > > > Signed-off-by: Yang Shi > > > --- > > > include/linux/memcontrol.h | 7 +++-- > > > mm/vmscan.c | 60 ++++++++++++++++++++++++++------------ > > > 2 files changed, 46 insertions(+), 21 deletions(-) > > > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > > index 4c9253896e25..c457fc7bc631 100644 > > > --- a/include/linux/memcontrol.h > > > +++ b/include/linux/memcontrol.h > > > @@ -93,12 +93,13 @@ struct lruvec_stat { > > > }; > > > > > > /* > > > - * Bitmap of shrinker::id corresponding to memcg-aware shrinkers, > > > - * which have elements charged to this memcg. > > > + * Bitmap and deferred work of shrinker::id corresponding to memcg-aware > > > + * shrinkers, which have elements charged to this memcg. > > > */ > > > struct shrinker_info { > > > struct rcu_head rcu; > > > - unsigned long map[]; > > > + atomic_long_t *nr_deferred; > > > + unsigned long *map; > > > }; > > > > > > /* > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > > index a1047ea60ecf..fcb399e18fc3 100644 > > > --- a/mm/vmscan.c > > > +++ b/mm/vmscan.c > > > @@ -187,11 +187,17 @@ static DECLARE_RWSEM(shrinker_rwsem); > > > #ifdef CONFIG_MEMCG > > > static int shrinker_nr_max; > > > > > > +/* The shrinker_info is expanded in a batch of BITS_PER_LONG */ > > > static inline int shrinker_map_size(int nr_items) > > > { > > > return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long)); > > > } > > > > > > +static inline int shrinker_defer_size(int nr_items) > > > +{ > > > + return (round_up(nr_items, BITS_PER_LONG) * sizeof(atomic_long_t)); > > > +} > > > + > > > static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg, > > > int nid) > > > { > > > @@ -200,10 +206,12 @@ static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg, > > > } > > > > > > static int expand_one_shrinker_info(struct mem_cgroup *memcg, > > > - int size, int old_size) > > > + int map_size, int defer_size, > > > + int old_map_size, int old_defer_size) > > > { > > > struct shrinker_info *new, *old; > > > int nid; > > > + int size = map_size + defer_size; > > > > > > for_each_node(nid) { > > > old = shrinker_info_protected(memcg, nid); > > > @@ -215,9 +223,16 @@ static int expand_one_shrinker_info(struct mem_cgroup *memcg, > > > if (!new) > > > return -ENOMEM; > > > > > > - /* Set all old bits, clear all new bits */ > > > - memset(new->map, (int)0xff, old_size); > > > - memset((void *)new->map + old_size, 0, size - old_size); > > > + new->nr_deferred = (atomic_long_t *)(new + 1); > > > + new->map = (void *)new->nr_deferred + defer_size; > > > + > > > + /* map: set all old bits, clear all new bits */ > > > + memset(new->map, (int)0xff, old_map_size); > > > + memset((void *)new->map + old_map_size, 0, map_size - old_map_size); > > > + /* nr_deferred: copy old values, clear all new values */ > > > + memcpy(new->nr_deferred, old->nr_deferred, old_defer_size); > > > + memset((void *)new->nr_deferred + old_defer_size, 0, > > > + defer_size - old_defer_size); > > > > > > rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, new); > > > kvfree_rcu(old); > > > @@ -232,9 +247,6 @@ void free_shrinker_info(struct mem_cgroup *memcg) > > > struct shrinker_info *info; > > > int nid; > > > > > > - if (mem_cgroup_is_root(memcg)) > > > - return; > > > - > > > for_each_node(nid) { > > > pn = mem_cgroup_nodeinfo(memcg, nid); > > > info = shrinker_info_protected(memcg, nid); > > > @@ -247,12 +259,12 @@ int alloc_shrinker_info(struct mem_cgroup *memcg) > > > { > > > struct shrinker_info *info; > > > int nid, size, ret = 0; > > > - > > > - if (mem_cgroup_is_root(memcg)) > > > - return 0; > > > > Can you please comment on the consequences on allowing to allocate > > shrinker_info for root memcg? Why didn't we do that before but now it > > is fine (or maybe required)? Please add the explanation in the commit > > message. > > Before the patchset shrinker_info just tracks shrinker_maps which is > not required for root memcg. But the newly added nr_deferred is needed > in root memcg otherwise the nr_deferred work would get lost once the > memcgs are reparented to root. > > How's about adding the below paragraph to the commit log: > > "To preserve nr_deferred when reparenting memcgs to root, root memcg > needs shrinker_info allocated too." > LGTM and you can add: Reviewed-by: Shakeel Butt