From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f72.google.com (mail-pl0-f72.google.com [209.85.160.72]) by kanga.kvack.org (Postfix) with ESMTP id 4F2FA6B0006 for ; Mon, 21 May 2018 05:17:18 -0400 (EDT) Received: by mail-pl0-f72.google.com with SMTP id a5-v6so9679483plp.8 for ; Mon, 21 May 2018 02:17:18 -0700 (PDT) Received: from EUR01-DB5-obe.outbound.protection.outlook.com (mail-db5eur01on0118.outbound.protection.outlook.com. [104.47.2.118]) by mx.google.com with ESMTPS id y7-v6si10816513pgv.409.2018.05.21.02.17.16 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 21 May 2018 02:17:17 -0700 (PDT) Subject: Re: [PATCH v6 14/17] mm: Iterate only over charged shrinkers during memcg shrink_slab() References: <152663268383.5308.8660992135988724014.stgit@localhost.localdomain> <152663304128.5308.12840831728812876902.stgit@localhost.localdomain> <20180520080003.gfygtb6rloqpjaol@esperanza> From: Kirill Tkhai Message-ID: <9eae0da6-5981-1ab2-af86-0a62ee31ba17@virtuozzo.com> Date: Mon, 21 May 2018 12:17:07 +0300 MIME-Version: 1.0 In-Reply-To: <20180520080003.gfygtb6rloqpjaol@esperanza> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vladimir Davydov Cc: akpm@linux-foundation.org, shakeelb@google.com, viro@zeniv.linux.org.uk, hannes@cmpxchg.org, mhocko@kernel.org, tglx@linutronix.de, pombredanne@nexb.com, stummala@codeaurora.org, gregkh@linuxfoundation.org, sfr@canb.auug.org.au, guro@fb.com, mka@chromium.org, penguin-kernel@I-love.SAKURA.ne.jp, chris@chris-wilson.co.uk, longman@redhat.com, minchan@kernel.org, ying.huang@intel.com, mgorman@techsingularity.net, jbacik@fb.com, linux@roeck-us.net, linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org, lirongqing@baidu.com, aryabinin@virtuozzo.com On 20.05.2018 11:00, Vladimir Davydov wrote: > On Fri, May 18, 2018 at 11:44:01AM +0300, Kirill Tkhai wrote: >> Using the preparations made in previous patches, in case of memcg >> shrink, we may avoid shrinkers, which are not set in memcg's shrinkers >> bitmap. To do that, we separate iterations over memcg-aware and >> !memcg-aware shrinkers, and memcg-aware shrinkers are chosen >> via for_each_set_bit() from the bitmap. In case of big nodes, >> having many isolated environments, this gives significant >> performance growth. See next patches for the details. >> >> Note, that the patch does not respect to empty memcg shrinkers, >> since we never clear the bitmap bits after we set it once. >> Their shrinkers will be called again, with no shrinked objects >> as result. This functionality is provided by next patches. >> >> Signed-off-by: Kirill Tkhai >> --- >> mm/vmscan.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++------ >> 1 file changed, 78 insertions(+), 9 deletions(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index f09ea20d7270..2fbf3b476601 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -373,6 +373,20 @@ int prealloc_shrinker(struct shrinker *shrinker) >> goto free_deferred; >> } >> >> + /* >> + * There is a window between prealloc_shrinker() >> + * and register_shrinker_prepared(). We don't want >> + * to clear bit of a shrinker in such the state >> + * in shrink_slab_memcg(), since this will impose >> + * restrictions on a code registering a shrinker >> + * (they would have to guarantee, their LRU lists >> + * are empty till shrinker is completely registered). >> + * So, we differ the situation, when 1)a shrinker >> + * is semi-registered (id is assigned, but it has >> + * not yet linked to shrinker_list) and 2)shrinker >> + * is not registered (id is not assigned). >> + */ >> + INIT_LIST_HEAD(&shrinker->list); >> return 0; >> >> free_deferred: >> @@ -544,6 +558,67 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, >> return freed; >> } >> >> +#ifdef CONFIG_MEMCG_KMEM >> +static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, >> + struct mem_cgroup *memcg, int priority) >> +{ >> + struct memcg_shrinker_map *map; >> + unsigned long freed = 0; >> + int ret, i; >> + >> + if (!memcg_kmem_enabled() || !mem_cgroup_online(memcg)) >> + return 0; >> + >> + if (!down_read_trylock(&shrinker_rwsem)) >> + return 0; >> + >> + /* >> + * 1) Caller passes only alive memcg, so map can't be NULL. >> + * 2) shrinker_rwsem protects from maps expanding. >> + */ >> + map = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_map, >> + true); >> + BUG_ON(!map); >> + >> + for_each_set_bit(i, map->map, memcg_shrinker_nr_max) { >> + struct shrink_control sc = { >> + .gfp_mask = gfp_mask, >> + .nid = nid, >> + .memcg = memcg, >> + }; >> + struct shrinker *shrinker; >> + >> + shrinker = idr_find(&shrinker_idr, i); >> + if (unlikely(!shrinker)) { > > Nit: I don't think 'unlikely' is required here as this is definitely not > a hot path. In case of big machines with many containers and overcommit, shrink_slab() in general is very hot path. See the patchset description. There are configurations, when only shrink_slab() is executing and occupies cpu for 100%, it's the reason of this patchset is made for. Here is the place we are absolutely sure shrinker is NULL in case if race with parallel registering, so I don't see anything wrong to give compiler some information about branch prediction. >> + clear_bit(i, map->map); >> + continue; >> + } >> + BUG_ON(!(shrinker->flags & SHRINKER_MEMCG_AWARE)); >> + >> + /* See comment in prealloc_shrinker() */ >> + if (unlikely(list_empty(&shrinker->list))) > > Ditto. > >> + continue; >> + >> + ret = do_shrink_slab(&sc, shrinker, priority); >> + freed += ret; >> + >> + if (rwsem_is_contended(&shrinker_rwsem)) { >> + freed = freed ? : 1; >> + break; >> + } >> + } >> + >> + up_read(&shrinker_rwsem); >> + return freed; >> +} >> +#else /* CONFIG_MEMCG_KMEM */ >> +static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, >> + struct mem_cgroup *memcg, int priority) >> +{ >> + return 0; >> +} >> +#endif /* CONFIG_MEMCG_KMEM */ >> + >> /** >> * shrink_slab - shrink slab caches >> * @gfp_mask: allocation context >> @@ -573,8 +648,8 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, >> struct shrinker *shrinker; >> unsigned long freed = 0; >> >> - if (memcg && (!memcg_kmem_enabled() || !mem_cgroup_online(memcg))) >> - return 0; >> + if (memcg && !mem_cgroup_is_root(memcg)) >> + return shrink_slab_memcg(gfp_mask, nid, memcg, priority); >> >> if (!down_read_trylock(&shrinker_rwsem)) >> goto out; >> @@ -586,13 +661,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, >> .memcg = memcg, >> }; >> >> - /* >> - * If kernel memory accounting is disabled, we ignore >> - * SHRINKER_MEMCG_AWARE flag and call all shrinkers >> - * passing NULL for memcg. >> - */ >> - if (memcg_kmem_enabled() && >> - !!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE)) >> + if (!!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE)) >> continue; >> >> if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) >>