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=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 4B573C433B4 for ; Mon, 12 Apr 2021 23:14:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BCF3C613A9 for ; Mon, 12 Apr 2021 23:14:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BCF3C613A9 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0C00C6B0036; Mon, 12 Apr 2021 19:14:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 049446B006E; Mon, 12 Apr 2021 19:14:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DDDB56B0070; Mon, 12 Apr 2021 19:14:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0116.hostedemail.com [216.40.44.116]) by kanga.kvack.org (Postfix) with ESMTP id BEC916B0036 for ; Mon, 12 Apr 2021 19:14:23 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 7495518026110 for ; Mon, 12 Apr 2021 23:14:23 +0000 (UTC) X-FDA: 78025270806.07.39F9B27 Received: from mail-lf1-f42.google.com (mail-lf1-f42.google.com [209.85.167.42]) by imf21.hostedemail.com (Postfix) with ESMTP id 766A0E000119 for ; Mon, 12 Apr 2021 23:14:21 +0000 (UTC) Received: by mail-lf1-f42.google.com with SMTP id b4so24100001lfi.6 for ; Mon, 12 Apr 2021 16:14:22 -0700 (PDT) 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=/duzMH/OTq6aaOv0cDTj1fS9M5eKwgWI2Ns6h3aePII=; b=NQ1YkeyiLSUMD3jWDiGlc6wYoFZTbrTUVCYIGGrWuZqu87Dn3X0VLGDBLQwLx7pKwu /JEpw2GxwEpZJiN7Q2hten9sbEV8lUkUN+HGTSj6WXhrUuK4B/ihsvysUzvp6jN1jrOT iJOX1wVmhk9ANkOmQy8M20dshGYkGVBzEgfR5cUuHTT4hRCKlNliYyge/CWCKShmjy9/ 0Wj2cykBVj6158M/fVwGueo1LTOzMAieRuPpe9Z2ULeCJfKHVWWN8hSkkaIQr+03gLIi 6bBbSqVV8/rNNlgMQ0QmCKi0Fs1IQQ6y0IbuwxbQbvKveEwvx7N+AQeCyMcOGKq+n/kv uP7Q== 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=/duzMH/OTq6aaOv0cDTj1fS9M5eKwgWI2Ns6h3aePII=; b=CigySYIBlXyDGOgv8s+OfqynxXB4MY/XxbwXT1YtsiJEYJ2gWh6F2aCgMbXc0MWR0C 50wC9/6igyzX6qz2VhSYAKfExF7vweKqbT6SHuZSCnBrYaS8f2QGqmVxHbdhw3K4PZwL kbAeH6yq5Lj4/KXUaruu6dfwHNCgosVi3nUd+X7C92ImScoRMX9dFp2IbfoSRRpqzD5m fdzeB7hxXG784Ecsh8E++6zilROxokqsS5nMZt5OC/n389K6y25COICX8XN/y/XmXYiZ VzLSymkl877rr7y0f/HP1dTAaS+QzUIDl/y6o2iKAMIbtdEPiLEX2HMx00cqpN6n4KaW Aq0g== X-Gm-Message-State: AOAM533jkXEq7wNAwfEiGBCM+6Y3wkuF739wv06FRQWlSN0iUdhSKCpI 9bTMgpWizdRVAU535KrDPJslN0cgTHSKRxgZCSwWPg== X-Google-Smtp-Source: ABdhPJzCyBQTUhS/VAijry16x1b+ynmJqq7HaLNObZMA41fFqdeUQTFoHoDT9JU3LYprSh+tTD9AYd0xB5Q0T/v2HzY= X-Received: by 2002:a05:6512:3703:: with SMTP id z3mr20217180lfr.358.1618269261596; Mon, 12 Apr 2021 16:14:21 -0700 (PDT) MIME-Version: 1.0 References: <20210412225503.15119-1-longman@redhat.com> <20210412225503.15119-6-longman@redhat.com> In-Reply-To: From: Shakeel Butt Date: Mon, 12 Apr 2021 16:14:10 -0700 Message-ID: Subject: Re: [PATCH v2 5/5] mm/memcg: Optimize user context object stock access To: Waiman Long Cc: Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Tejun Heo , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , LKML , Cgroups , Linux MM , Muchun Song , Alex Shi , Chris Down , Yafang Shao , Wei Yang , Masayoshi Mizuma , Xing Zhengjun Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 766A0E000119 X-Stat-Signature: 3yquyrqjcxjrxepg1gpim39hg9fpdkyd X-Rspamd-Server: rspam02 Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf21; identity=mailfrom; envelope-from=""; helo=mail-lf1-f42.google.com; client-ip=209.85.167.42 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618269261-854120 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 Mon, Apr 12, 2021 at 4:10 PM Shakeel Butt wrote: > > On Mon, Apr 12, 2021 at 3:55 PM Waiman Long wrote: > > > > Most kmem_cache_alloc() calls are from user context. With instrumentation > > enabled, the measured amount of kmem_cache_alloc() calls from non-task > > context was about 0.01% of the total. > > > > The irq disable/enable sequence used in this case to access content > > from object stock is slow. To optimize for user context access, there > > are now two object stocks for task context and interrupt context access > > respectively. > > > > The task context object stock can be accessed after disabling preemption > > which is cheap in non-preempt kernel. The interrupt context object stock > > can only be accessed after disabling interrupt. User context code can > > access interrupt object stock, but not vice versa. > > > > The mod_objcg_state() function is also modified to make sure that memcg > > and lruvec stat updates are done with interrupted disabled. > > > > The downside of this change is that there are more data stored in local > > object stocks and not reflected in the charge counter and the vmstat > > arrays. However, this is a small price to pay for better performance. > > > > Signed-off-by: Waiman Long > > Acked-by: Roman Gushchin > > --- > > mm/memcontrol.c | 73 +++++++++++++++++++++++++++++++++++++++---------- > > 1 file changed, 59 insertions(+), 14 deletions(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 69f728383efe..29f2df76644a 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -2229,7 +2229,8 @@ struct obj_stock { > > struct memcg_stock_pcp { > > struct mem_cgroup *cached; /* this never be root cgroup */ > > unsigned int nr_pages; > > - struct obj_stock obj; > > + struct obj_stock task_obj; > > + struct obj_stock irq_obj; > > > > struct work_struct work; > > unsigned long flags; > > @@ -2254,11 +2255,48 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock, > > } > > #endif > > > > +/* > > + * Most kmem_cache_alloc() calls are from user context. The irq disable/enable > > + * sequence used in this case to access content from object stock is slow. > > + * To optimize for user context access, there are now two object stocks for > > + * task context and interrupt context access respectively. > > + * > > + * The task context object stock can be accessed by disabling preemption only > > + * which is cheap in non-preempt kernel. The interrupt context object stock > > + * can only be accessed after disabling interrupt. User context code can > > + * access interrupt object stock, but not vice versa. > > + */ > > static inline struct obj_stock *current_obj_stock(void) > > { > > struct memcg_stock_pcp *stock = this_cpu_ptr(&memcg_stock); > > > > - return &stock->obj; > > + return in_task() ? &stock->task_obj : &stock->irq_obj; > > +} > > + > > +#define get_obj_stock(flags) \ > > +({ \ > > + struct memcg_stock_pcp *stock; \ > > + struct obj_stock *obj_stock; \ > > + \ > > + if (in_task()) { \ > > + preempt_disable(); \ > > + (flags) = -1L; \ > > + stock = this_cpu_ptr(&memcg_stock); \ > > The above line was missing in the previous version. > > > + obj_stock = &stock->task_obj; \ > > + } else { \ > > + local_irq_save(flags); \ > > + stock = this_cpu_ptr(&memcg_stock); \ > > + obj_stock = &stock->irq_obj; \ > > + } \ > > + obj_stock; \ > > +}) > > + > > +static inline void put_obj_stock(unsigned long flags) > > +{ > > + if (flags == -1L) > > + preempt_enable(); > > + else > > + local_irq_restore(flags); > > } > > > > /** > > @@ -2327,7 +2365,9 @@ static void drain_local_stock(struct work_struct *dummy) > > local_irq_save(flags); > > > > stock = this_cpu_ptr(&memcg_stock); > > - drain_obj_stock(&stock->obj); > > + drain_obj_stock(&stock->irq_obj); > > + if (in_task()) > > + drain_obj_stock(&stock->task_obj); > > drain_stock(stock); > > clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); > > > > @@ -3183,7 +3223,7 @@ static inline void mod_objcg_state(struct obj_cgroup *objcg, > > memcg = obj_cgroup_memcg(objcg); > > if (pgdat) > > lruvec = mem_cgroup_lruvec(memcg, pgdat); > > - __mod_memcg_lruvec_state(memcg, lruvec, idx, nr); > > + mod_memcg_lruvec_state(memcg, lruvec, idx, nr); > > rcu_read_unlock(); > > } > > > > @@ -3193,7 +3233,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes) > > unsigned long flags; > > bool ret = false; > > > > - local_irq_save(flags); > > + stock = get_obj_stock(flags); > > > > stock = current_obj_stock(); > > The above is redundant. > After cleanup you can add: Reviewed-by: Shakeel Butt