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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED 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 8FA6FC433E6 for ; Sun, 24 Jan 2021 05:01:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6AC1B227BF for ; Sun, 24 Jan 2021 05:01:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725925AbhAXFBu (ORCPT ); Sun, 24 Jan 2021 00:01:50 -0500 Received: from mail.kernel.org ([198.145.29.99]:46900 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725803AbhAXFBt (ORCPT ); Sun, 24 Jan 2021 00:01:49 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id DD67122CAF; Sun, 24 Jan 2021 05:01:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1611464468; bh=v4lR/kqZFRCCNu+1PsQARvAPeB5fTJSYEm5bicK1Y70=; h=Date:From:To:Subject:In-Reply-To:From; b=Nku7JUjIHcZtLpNBL3Qw20IjwbmS/uNiPl7GkC3yTCjlEfUF51gd3dgSvWrPWvfae gkceWAtj9eZKmPpzBP1jWwVpa1zMN/xeCVlcukJKJdXKo1q7cXJSZQrZrKdOg2e3RT 7Nm1zHW/uR3KWHT3Zp+Jdc3pFXBmCVAkOh5dylPo= Date: Sat, 23 Jan 2021 21:01:07 -0800 From: Andrew Morton To: akpm@linux-foundation.org, guro@fb.com, hannes@cmpxchg.org, imran.f.khan@oracle.com, linux-mm@kvack.org, mkoutny@suse.com, mm-commits@vger.kernel.org, shakeelb@google.com, stable@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 03/19] mm: memcg/slab: optimize objcg stock draining Message-ID: <20210124050107.0rcfKNymq%akpm@linux-foundation.org> In-Reply-To: <20210123210029.a7c704d0cab204683e41ad10@linux-foundation.org> User-Agent: s-nail v14.8.16 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org =46rom: Roman Gushchin Subject: mm: memcg/slab: optimize objcg stock draining Imran Khan reported a 16% regression in hackbench results caused by the commit f2fe7b09a52b ("mm: memcg/slab: charge individual slab objects instead of pages"). The regression is noticeable in the case of a consequent allocation of several relatively large slab objects, e.g.=20 skb's. As soon as the amount of stocked bytes exceeds PAGE_SIZE, drain_obj_stock() and __memcg_kmem_uncharge() are called, and it leads to a number of atomic operations in page_counter_uncharge(). The corresponding call graph is below (provided by Imran Khan): |__alloc_skb | | | |__kmalloc_reserve.isra.61 | | | | | |__kmalloc_node_track_caller | | | | | | | |slab_pre_alloc_hook.constprop.88 | | | obj_cgroup_charge | | | | | | | | | |__memcg_kmem_charge | | | | | | | | | | | |page_counter_try_charge | | | | | | | | | |refill_obj_stock | | | | | | | | | | | |drain_obj_stock.isra.68 | | | | | | | | | | | | | |__memcg_kmem_uncharge | | | | | | | | | | | | | | | |page_counter_uncharge | | | | | | | | | | | | | | | | | |page_counter_cancel | | | | | | | | | | | |__slab_alloc | | | | | | | | | |___slab_alloc | | | | | | | | |slab_post_alloc_hook Instead of directly uncharging the accounted kernel memory, it's possible to refill the generic page-sized per-cpu stock instead. It's a much faster operation, especially on a default hierarchy. As a bonus, __memcg_kmem_uncharge_page() will also get faster, so the freeing of page-sized kernel allocations (e.g. large kmallocs) will become faster. A similar change has been done earlier for the socket memory by the commit 475d0487a2ad ("mm: memcontrol: use per-cpu stocks for socket memory uncharging"). Link: https://lkml.kernel.org/r/20210106042239.2860107-1-guro@fb.com Fixes: f2fe7b09a52b ("mm: memcg/slab: charge individual slab objects instea= d of pages") Signed-off-by: Roman Gushchin Reported-by: Imran Khan Tested-by: Imran Khan Reviewed-by: Shakeel Butt Reviewed-by: Michal Koutn Cc: Michal Koutn=C3=BD Cc: Johannes Weiner Cc: Signed-off-by: Andrew Morton --- mm/memcontrol.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/mm/memcontrol.c~mm-memcg-slab-optimize-objcg-stock-draining +++ a/mm/memcontrol.c @@ -3115,9 +3115,7 @@ void __memcg_kmem_uncharge(struct mem_cg if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) page_counter_uncharge(&memcg->kmem, nr_pages); =20 - page_counter_uncharge(&memcg->memory, nr_pages); - if (do_memsw_account()) - page_counter_uncharge(&memcg->memsw, nr_pages); + refill_stock(memcg, nr_pages); } =20 /** _