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 A194EC433EF for ; Tue, 8 Mar 2022 04:39:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B65C58D0002; Mon, 7 Mar 2022 23:39:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B15F08D0001; Mon, 7 Mar 2022 23:39:56 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A04448D0002; Mon, 7 Mar 2022 23:39:56 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0193.hostedemail.com [216.40.44.193]) by kanga.kvack.org (Postfix) with ESMTP id 8D30A8D0001 for ; Mon, 7 Mar 2022 23:39:56 -0500 (EST) Received: from smtpin31.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 47C7995B0F for ; Tue, 8 Mar 2022 04:39:56 +0000 (UTC) X-FDA: 79219966392.31.4F17A6B Received: from out0.migadu.com (out0.migadu.com [94.23.1.103]) by imf31.hostedemail.com (Postfix) with ESMTP id 60B7C20008 for ; Tue, 8 Mar 2022 04:39:55 +0000 (UTC) Date: Mon, 7 Mar 2022 20:39:45 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1646714393; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Oqg4FK2E02yUZ3pAW+Qrnt3Pk7Nlrsl6nBcS0deBrTU=; b=mvWpkTv/kqQIyYzCAaonqDgaCKq96kChTppQ73G3QurJrXOGI/FB3nNrkGkSrUV0DFgb9A bTmjAISmYwUgDVuZ9KPXWnq2KH9mWy5kBH7rHjJ2/5+lbBRNsjgy1IgR+io/7uUC5o1jIS T810bTl+7hjhqNkkQYN0VXg43BeliPM= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Roman Gushchin To: Waiman Long Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song Subject: Re: [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node() Message-ID: References: <20220308033009.1400464-1-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220308033009.1400464-1-longman@redhat.com> X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 60B7C20008 X-Rspam-User: Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="mvWpkTv/"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf31.hostedemail.com: domain of roman.gushchin@linux.dev designates 94.23.1.103 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev X-Stat-Signature: oiumrhn3e9gcwi7f75qozic9mxrbre7s X-HE-Tag: 1646714395-83726 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, Mar 07, 2022 at 10:30:09PM -0500, Waiman Long wrote: > Since commit 2c80cd57c743 ("mm/list_lru.c: fix list_lru_count_node() > to be race free"), we are tracking the total number of lru > entries in a list_lru_node in its nr_items field. In the case of > memcg_drain_list_lru_node(), there is nothing to be done if nr_items > is 0. We don't even need to take the nlru->lock as no new lru entry > could be added by a racing list_lru_add() to the draining src_idx memcg > at this point. > > Signed-off-by: Waiman Long Hi Waiman! The patch makes total sense to me, however it needs to be rebased at least on top of "mm: list_lru: rename memcg_drain_all_list_lrus to memcg_reparent_list_lrus". Thanks! > --- > mm/list_lru.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/list_lru.c b/mm/list_lru.c > index 0cd5e89ca063..100ca453e885 100644 > --- a/mm/list_lru.c > +++ b/mm/list_lru.c > @@ -518,6 +518,12 @@ static void memcg_drain_list_lru_node(struct list_lru *lru, int nid, > int dst_idx = dst_memcg->kmemcg_id; > struct list_lru_one *src, *dst; > > + /* > + * If there is no lru entry in this nlru, we can skip it immediately. > + */ > + if (!READ_ONCE(nlru->nr_items)) > + return; > + > /* > * Since list_lru_{add,del} may be called under an IRQ-safe lock, > * we have to use IRQ-safe primitives here to avoid deadlock. > -- > 2.27.0 > >