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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 72BEDC433EF for ; Fri, 24 Jun 2022 04:14:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 128378E01C6; Fri, 24 Jun 2022 00:14:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0D6D98E01BF; Fri, 24 Jun 2022 00:14:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EE0718E01C6; Fri, 24 Jun 2022 00:14:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id DB9D48E01BF for ; Fri, 24 Jun 2022 00:14:03 -0400 (EDT) Received: from smtpin31.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 9EADA213E9 for ; Fri, 24 Jun 2022 04:14:03 +0000 (UTC) X-FDA: 79611811566.31.EC9EC9B Received: from mail-yb1-f173.google.com (mail-yb1-f173.google.com [209.85.219.173]) by imf08.hostedemail.com (Postfix) with ESMTP id 484EA160026 for ; Fri, 24 Jun 2022 04:14:03 +0000 (UTC) Received: by mail-yb1-f173.google.com with SMTP id r3so2523416ybr.6 for ; Thu, 23 Jun 2022 21:14:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=1qA3djIvmCXy0qDgHJwJPAvZJI/yB7Iv/v6zV71DlqI=; b=dbZ9+ZC5GXZBRWNne1PZdMvrN9BTVVpQyaGafXlsAtWJeAd9l8oyXDXIqFysIl9GVm N4H+lFbi6/LBOckdOGoUbN7WtfvcNbNBOeOFC7rh5NtINkkrczh+6eZUtMSYo2E3AY9Q KYGicWB9gM91hpq5XTmgvSFGXfHwUfmiFGF4JIDqGyLQZ9Ioy2r1nLhocjJhDW2tTunF +GaqHi5XbJRMj4kjJ73QHO1rFkP1twxXYdL2Vjmx+CyHxUvo5vkbtNGr14PQ0ANIM6bW nq7VV+wsKB9fTNwybydirk3rRQxeekz89JST0ITd5vaJmhm+joNueRsC/J/thMNGvbjz MofQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1qA3djIvmCXy0qDgHJwJPAvZJI/yB7Iv/v6zV71DlqI=; b=OPeK9Ud+7cr99EJPr7Y/XsZKmYPQNjd54WxhNjdq2RaqJ6c8XCTnf4g1hEuGAwpr8f VeZ0LWfzMOmGE++dXMUyOKu6DiCXkb+KPY0qbLLJ/S9GiJxM01yKORzFHvaD3wjx4k5h RZugtivuLkMF5+Tg5apRzrtLYXAg5rVE/lTJqUI3ixiD7nJltmocfK3VxMjw4D34ghHS C60Ve/W1+mkiMJOFBYIkb49Yi1cb/XikhzlHEtLj8s5TDG/9AUgz3oqApNX6kMSBzTwW IIgwSXuwLXP38P/5iTS+2yZsK4nj7GTeiwjJ7knpiJTIHH6uFLEaLNTchCMDzBEDhVld /dsw== X-Gm-Message-State: AJIora+KAwTGl8CWkwp//ImXFWSWcw1yO8m2DXXDNHVL9N6uNkHYhk48 CbYKC3jNF6SLueyE/+34rXGwk59K/YY8mt9Jh3XXuQ== X-Google-Smtp-Source: AGRyM1u5NmicPX8kPXvz1kiPZ+hNXNfnIUMJsLYPxSR6t62siw34qIBUx64zMORNQHZNj8XRPh/W7Dh2yu7XetMiJhw= X-Received: by 2002:a25:6c5:0:b0:669:a17a:2289 with SMTP id 188-20020a2506c5000000b00669a17a2289mr9871960ybg.231.1656044042254; Thu, 23 Jun 2022 21:14:02 -0700 (PDT) MIME-Version: 1.0 References: <20220619150456.GB34471@xsang-OptiPlex-9020> <20220622172857.37db0d29@kernel.org> <20220623185730.25b88096@kernel.org> In-Reply-To: <20220623185730.25b88096@kernel.org> From: Eric Dumazet Date: Fri, 24 Jun 2022 06:13:51 +0200 Message-ID: Subject: Re: [net] 4890b686f4: netperf.Throughput_Mbps -69.4% regression To: Jakub Kicinski Cc: Xin Long , Marcelo Ricardo Leitner , kernel test robot , Shakeel Butt , Soheil Hassas Yeganeh , LKML , Linux Memory Management List , network dev , linux-s390@vger.kernel.org, MPTCP Upstream , "linux-sctp @ vger . kernel . org" , lkp@lists.01.org, kbuild test robot , Huang Ying , "Tang, Feng" , zhengjun.xing@linux.intel.com, fengwei.yin@intel.com, Ying Xu Content-Type: text/plain; charset="UTF-8" ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=dbZ9+ZC5; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf08.hostedemail.com: domain of edumazet@google.com designates 209.85.219.173 as permitted sender) smtp.mailfrom=edumazet@google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656044043; a=rsa-sha256; cv=none; b=6Vu6yyEDDLptLRbkKBCTJ0nkJKnU+DphdjQBdxoAJGdB9aQPXBOlbUuoepMpoQgiKOjLfb 3Pf1NfZZ8FRDXwOB8nnYUbjh77XO9s2eqlUAzdFgVhVDFc9HfFTaDEepnyuzm2X7kKlKKA mZSfi2PkTd0d157bTR+h2wHfUvzTUWw= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656044043; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=1qA3djIvmCXy0qDgHJwJPAvZJI/yB7Iv/v6zV71DlqI=; b=UXD7upHvmZOjPCCJuodVLS256XXTRLi7YVDUnBm/5LjNZKVXRWjD5bjsdKr+GpJahPBGCH 9Vjc78ITNVDz8bGB7zxEjZTpm7lkAKccAzR5Q8m8C8ygkxrXmat8SAoKH+uXqFCKGNlr4D EWekiZE5307F3gc5CCQh+XkSm7ezvFU= X-Stat-Signature: eebzskwn6j19jn9xu8u8ezh96pshzyg8 X-Rspamd-Server: rspam08 X-Rspam-User: X-Rspamd-Queue-Id: 484EA160026 Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=dbZ9+ZC5; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf08.hostedemail.com: domain of edumazet@google.com designates 209.85.219.173 as permitted sender) smtp.mailfrom=edumazet@google.com X-HE-Tag: 1656044043-865328 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 Fri, Jun 24, 2022 at 3:57 AM Jakub Kicinski wrote: > > On Thu, 23 Jun 2022 18:50:07 -0400 Xin Long wrote: > > From the perf data, we can see __sk_mem_reduce_allocated() is the one > > using CPU the most more than before, and mem_cgroup APIs are also > > called in this function. It means the mem cgroup must be enabled in > > the test env, which may explain why I couldn't reproduce it. > > > > The Commit 4890b686f4 ("net: keep sk->sk_forward_alloc as small as > > possible") uses sk_mem_reclaim(checking reclaimable >= PAGE_SIZE) to > > reclaim the memory, which is *more frequent* to call > > __sk_mem_reduce_allocated() than before (checking reclaimable >= > > SK_RECLAIM_THRESHOLD). It might be cheap when > > mem_cgroup_sockets_enabled is false, but I'm not sure if it's still > > cheap when mem_cgroup_sockets_enabled is true. > > > > I think SCTP netperf could trigger this, as the CPU is the bottleneck > > for SCTP netperf testing, which is more sensitive to the extra > > function calls than TCP. > > > > Can we re-run this testing without mem cgroup enabled? > > FWIW I defer to Eric, thanks a lot for double checking the report > and digging in! I did tests with TCP + memcg and noticed a very small additional cost in memcg functions, because of suboptimal layout: Extract of an internal Google bug, update from June 9th: -------------------------------- I have noticed a minor false sharing to fetch (struct mem_cgroup)->css.parent, at offset 0xc0, because it shares the cache line containing struct mem_cgroup.memory, at offset 0xd0 Ideally, memcg->socket_pressure and memcg->parent should sit in a read mostly cache line. ----------------------- But nothing that could explain a "-69.4% regression" memcg has a very similar strategy of per-cpu reserves, with MEMCG_CHARGE_BATCH being 32 pages per cpu. It is not clear why SCTP with 10K writes would overflow this reserve constantly. Presumably memcg experts will have to rework structure alignments to make sure they can cope better with more charge/uncharge operations, because we are not going back to gigantic per-socket reserves, this simply does not scale.