From patchwork Fri Apr 9 23:18:42 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 12195221 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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 E9DA0C43462 for ; Fri, 9 Apr 2021 23:19:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9C3ED610A6 for ; Fri, 9 Apr 2021 23:19:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9C3ED610A6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B05E26B0073; Fri, 9 Apr 2021 19:19:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AB6F76B0074; Fri, 9 Apr 2021 19:19:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 894AC6B0075; Fri, 9 Apr 2021 19:19:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0094.hostedemail.com [216.40.44.94]) by kanga.kvack.org (Postfix) with ESMTP id 2C66A6B0073 for ; Fri, 9 Apr 2021 19:19:42 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id E83E4181D75AB for ; Fri, 9 Apr 2021 23:19:41 +0000 (UTC) X-FDA: 78014397762.18.B325D52 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf08.hostedemail.com (Postfix) with ESMTP id 296E680192D5 for ; Fri, 9 Apr 2021 23:19:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618010381; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:in-reply-to:in-reply-to:references:references; bh=VV6+ghNH1/AQ98hZ8A1K9EsRVAqRThkZsOYM3AOhXtQ=; b=U9P6F80ihpeprx0Kyuq97PW0JAH2Baa5O2x8Wtts6I08aOLBslR/N6he2fTE5NsomHCXaC ylckoa2vW9xE9xucQGGsJtLbpSByDOSx4NXofYBUJVrbEx3F/fKo/bABiAh+Or7ks+fDFh EeP4D35j20p0wWbJ1qcAKChrNc0OtsI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-317-KuKrdhoMNLmBEUiaohrPzA-1; Fri, 09 Apr 2021 19:19:39 -0400 X-MC-Unique: KuKrdhoMNLmBEUiaohrPzA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5D8931020C20; Fri, 9 Apr 2021 23:19:36 +0000 (UTC) Received: from llong.com (ovpn-113-226.rdu2.redhat.com [10.10.113.226]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6B4FC1B400; Fri, 9 Apr 2021 23:19:34 +0000 (UTC) From: Waiman Long To: Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Tejun Heo , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Shakeel Butt , Muchun Song , Alex Shi , Chris Down , Yafang Shao , Alexander Duyck , Wei Yang , Masayoshi Mizuma , Waiman Long Subject: [PATCH 5/5] mm/memcg: Optimize user context object stock access Date: Fri, 9 Apr 2021 19:18:42 -0400 Message-Id: <20210409231842.8840-6-longman@redhat.com> In-Reply-To: <20210409231842.8840-1-longman@redhat.com> References: <20210409231842.8840-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 296E680192D5 X-Stat-Signature: da7w6wjzya9rxnz5ochqu3pjxwyfffuf Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf08; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=216.205.24.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618010372-675554 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: 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 Reported-by: kernel test robot Acked-by: Roman Gushchin --- mm/memcontrol.c | 71 +++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 57 insertions(+), 14 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 69f728383efe..00c9074e42e5 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 +2255,46 @@ 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; \ + obj_stock = &stock->task_obj; \ + } else { \ + local_irq_save(flags); \ + 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 +2363,9 @@ 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 +3221,7 @@ 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 +3231,7 @@ 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(); if (objcg == stock->cached_objcg && stock->nr_bytes >= nr_bytes) { @@ -3201,7 +3239,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes) ret = true; } - local_irq_restore(flags); + put_obj_stock(flags); return ret; } @@ -3254,8 +3292,13 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock, { struct mem_cgroup *memcg; - if (stock->obj.cached_objcg) { - memcg = obj_cgroup_memcg(stock->obj.cached_objcg); + if (in_task() && stock->task_obj.cached_objcg) { + memcg = obj_cgroup_memcg(stock->task_obj.cached_objcg); + if (memcg && mem_cgroup_is_descendant(memcg, root_memcg)) + return true; + } + if (stock->irq_obj.cached_objcg) { + memcg = obj_cgroup_memcg(stock->irq_obj.cached_objcg); if (memcg && mem_cgroup_is_descendant(memcg, root_memcg)) return true; } @@ -3283,9 +3326,9 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes) { unsigned long flags; - local_irq_save(flags); + get_obj_stock(flags); __refill_obj_stock(objcg, nr_bytes); - local_irq_restore(flags); + put_obj_stock(flags); } static void __mod_obj_stock_state(struct obj_cgroup *objcg, @@ -3325,9 +3368,9 @@ void mod_obj_stock_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, { unsigned long flags; - local_irq_save(flags); + get_obj_stock(flags); __mod_obj_stock_state(objcg, pgdat, idx, nr); - local_irq_restore(flags); + put_obj_stock(flags); } int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size) @@ -3380,10 +3423,10 @@ void obj_cgroup_uncharge_mod_state(struct obj_cgroup *objcg, size_t size, { unsigned long flags; - local_irq_save(flags); + get_obj_stock(flags); __refill_obj_stock(objcg, size); __mod_obj_stock_state(objcg, pgdat, idx, -(int)size); - local_irq_restore(flags); + put_obj_stock(flags); } #endif /* CONFIG_MEMCG_KMEM */