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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 4D9BBC433E0 for ; Fri, 29 Jan 2021 14:46:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A3D5764E03 for ; Fri, 29 Jan 2021 14:46:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A3D5764E03 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=virtuozzo.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2805B6B0005; Fri, 29 Jan 2021 09:46:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 230FB6B0006; Fri, 29 Jan 2021 09:46:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 16EE36B006C; Fri, 29 Jan 2021 09:46:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id F2A326B0005 for ; Fri, 29 Jan 2021 09:46:40 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id AC365181AEF2A for ; Fri, 29 Jan 2021 14:46:40 +0000 (UTC) X-FDA: 77759088960.27.berry27_2f0920c275a9 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 8945C3D669 for ; Fri, 29 Jan 2021 14:46:40 +0000 (UTC) X-HE-Tag: berry27_2f0920c275a9 X-Filterd-Recvd-Size: 9209 Received: from relay.sw.ru (relay.sw.ru [185.231.240.75]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Fri, 29 Jan 2021 14:46:39 +0000 (UTC) Received: from [192.168.15.12] by relay.sw.ru with esmtp (Exim 4.94) (envelope-from ) id 1l5V2H-0017Ta-7n; Fri, 29 Jan 2021 17:46:09 +0300 Subject: Re: [v5 PATCH 07/11] mm: vmscan: add per memcg shrinker nr_deferred To: Vlastimil Babka , Yang Shi , guro@fb.com, shakeelb@google.com, david@fromorbit.com, hannes@cmpxchg.org, mhocko@suse.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210127233345.339910-1-shy828301@gmail.com> <20210127233345.339910-8-shy828301@gmail.com> <6b0638ba-2513-67f5-8ef1-9e60a7d9ded6@suse.cz> From: Kirill Tkhai Message-ID: Date: Fri, 29 Jan 2021 17:46:10 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <6b0638ba-2513-67f5-8ef1-9e60a7d9ded6@suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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: On 29.01.2021 16:00, Vlastimil Babka wrote: > On 1/28/21 12:33 AM, 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 ration 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 | 48 +++++++++++++++++++++++++------------- >> 2 files changed, 36 insertions(+), 19 deletions(-) >> >> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h >> index 62b888b88a5f..e0384367e07d 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[]; >> + unsigned long *map; >> + atomic_long_t *nr_deferred; >> }; >> >> /* >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 256896d157d4..20be0db291fe 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -187,16 +187,21 @@ static DECLARE_RWSEM(shrinker_rwsem); >> #ifdef CONFIG_MEMCG >> static int shrinker_nr_max; >> >> +#define NR_MAX_TO_SHR_MAP_SIZE(nr_max) \ >> + ((nr_max / BITS_PER_LONG + 1) * sizeof(unsigned long)) > > Could have been part of patch 4 already. And yeah, using DIV_ROUND_UP(), as > being hidden in a macro makes the "shorter statement" benefit disappear :) This was requested by me, and I am agree with Vlastimil using DIV_ROUND_UP() is OK. >> + >> static void free_shrinker_info_rcu(struct rcu_head *head) >> { >> kvfree(container_of(head, struct shrinker_info, rcu)); >> } >> >> static int expand_one_shrinker_info(struct mem_cgroup *memcg, >> - int size, int old_size) >> + int m_size, int d_size, >> + int old_m_size, int old_d_size) >> { >> struct shrinker_info *new, *old; >> int nid; >> + int size = m_size + d_size; >> >> for_each_node(nid) { >> old = rcu_dereference_protected( >> @@ -209,9 +214,15 @@ 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->map = (unsigned long *)(new + 1); >> + new->nr_deferred = (void *)new->map + m_size; > > This better be aligned to sizeof(atomic_long_t). Can we be sure about that? > Also it's all quite ugly and complex. Is it worth it? What about just leaving > map as it is and allocating a nr_deferred array separately, i.e.: > > struct shrinker_info { > struct rcu_head rcu; > atomic_long_t *nr_deferred; // allocated separately > unsigned long map[]; > }; Hm, don't two kvmalloc()'ed areas placed together occupy less memory?! nr_deferred easily can occupy n pages + small tail bytes since 4096/8 is just 512 shrinkers. >> + /* map: set all old bits, clear all new bits */ >> + memset(new->map, (int)0xff, old_m_size); >> + memset((void *)new->map + old_m_size, 0, m_size - old_m_size); >> + /* nr_deferred: copy old values, clear all new values */ >> + memcpy(new->nr_deferred, old->nr_deferred, old_d_size); >> + memset((void *)new->nr_deferred + old_d_size, 0, d_size - old_d_size); >> >> rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, new); >> call_rcu(&old->rcu, free_shrinker_info_rcu); >> @@ -226,9 +237,6 @@ 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 = rcu_dereference_protected(pn->shrinker_info, true); >> @@ -242,12 +250,13 @@ 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; >> + int m_size, d_size = 0; >> >> down_write(&shrinker_rwsem); >> - size = (shrinker_nr_max / BITS_PER_LONG + 1) * sizeof(unsigned long); >> + m_size = NR_MAX_TO_SHR_MAP_SIZE(shrinker_nr_max); >> + d_size = shrinker_nr_max * sizeof(atomic_long_t); >> + size = m_size + d_size; >> + >> for_each_node(nid) { >> info = kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid); >> if (!info) { >> @@ -255,6 +264,8 @@ int alloc_shrinker_info(struct mem_cgroup *memcg) >> ret = -ENOMEM; >> break; >> } >> + info->map = (unsigned long *)(info + 1); >> + info->nr_deferred = (void *)info->map + m_size; >> rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info); >> } >> up_write(&shrinker_rwsem); >> @@ -266,10 +277,16 @@ static int expand_shrinker_info(int new_id) >> { >> int size, old_size, ret = 0; >> int new_nr_max = new_id + 1; >> + int m_size, d_size = 0; >> + int old_m_size, old_d_size = 0; >> struct mem_cgroup *memcg; >> >> - size = (new_nr_max / BITS_PER_LONG + 1) * sizeof(unsigned long); >> - old_size = (shrinker_nr_max / BITS_PER_LONG + 1) * sizeof(unsigned long); >> + m_size = NR_MAX_TO_SHR_MAP_SIZE(new_nr_max); >> + d_size = new_nr_max * sizeof(atomic_long_t); >> + size = m_size + d_size; >> + old_m_size = NR_MAX_TO_SHR_MAP_SIZE(shrinker_nr_max); >> + old_d_size = shrinker_nr_max * sizeof(atomic_long_t); >> + old_size = old_m_size + old_d_size; >> if (size <= old_size) >> goto out; >> >> @@ -278,9 +295,8 @@ static int expand_shrinker_info(int new_id) >> >> memcg = mem_cgroup_iter(NULL, NULL, NULL); >> do { >> - if (mem_cgroup_is_root(memcg)) >> - continue; >> - ret = expand_one_shrinker_info(memcg, size, old_size); >> + ret = expand_one_shrinker_info(memcg, m_size, d_size, >> + old_m_size, old_d_size); >> if (ret) { >> mem_cgroup_iter_break(NULL, memcg); >> goto out; >> >