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 EFB47C433EF for ; Wed, 24 Nov 2021 16:32:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7242D6B0075; Wed, 24 Nov 2021 11:32:10 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6D3FC6B0078; Wed, 24 Nov 2021 11:32:10 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5C2466B007B; Wed, 24 Nov 2021 11:32:10 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0071.hostedemail.com [216.40.44.71]) by kanga.kvack.org (Postfix) with ESMTP id 4D4CA6B0075 for ; Wed, 24 Nov 2021 11:32:10 -0500 (EST) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 199DE816C7C4 for ; Wed, 24 Nov 2021 16:32:00 +0000 (UTC) X-FDA: 78844365600.21.7295357 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by imf12.hostedemail.com (Postfix) with ESMTP id 541F810003DD for ; Wed, 24 Nov 2021 16:31:59 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 3367B21954; Wed, 24 Nov 2021 16:31:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1637771518; h=from:from:reply-to: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=4Zlxw+Rp7HNPM08yf9RQ2otAy6kMKKm82h1DuizBhVs=; b=kvlaZyAZtdO4xGJaVhlIbgldeZDe8dWDxYpweto04dNhK1HokcngfkMFYHnNhQ1FIoqcKY czfjxXpIhR8yBj9ho9sTua3vCySoFNJoVI4oj93jjj75cASczmfdA3axwSPaU9Hnz5d/Ed nRrVTk/DxaqY6WuhTRi4RMh5BmMNbTY= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 007D4A3B8A; Wed, 24 Nov 2021 16:31:57 +0000 (UTC) Date: Wed, 24 Nov 2021 17:31:57 +0100 From: Michal Hocko To: Hao Lee Cc: linux-mm@kvack.org, hannes@cmpxchg.org, vdavydov.dev@gmail.com, shakeelb@google.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: reduce spinlock contention in release_pages() Message-ID: References: <20211124151915.GA6163@haolee.io> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211124151915.GA6163@haolee.io> X-Rspamd-Queue-Id: 541F810003DD X-Stat-Signature: 4m78p7i83cqip74nbqktqmcfh6mtzsf6 Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=kvlaZyAZ; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf12.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=mhocko@suse.com X-Rspamd-Server: rspam02 X-HE-Tag: 1637771519-565041 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 Wed 24-11-21 15:19:15, Hao Lee wrote: > When several tasks are terminated simultaneously, lots of pages will be > released, which can cause severe spinlock contention. Other tasks which > are running on the same core will be seriously affected. We can yield > cpu to fix this problem. How does this actually address the problem? You are effectivelly losing fairness completely. We do batch currently so no single task should be able to monopolize the cpu for too long. Why this is not sufficient? > diff --git a/mm/swap.c b/mm/swap.c > index e8c9dc6d0377..91850d51a5a5 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -960,8 +960,14 @@ void release_pages(struct page **pages, int nr) > if (PageLRU(page)) { > struct lruvec *prev_lruvec = lruvec; > > - lruvec = folio_lruvec_relock_irqsave(folio, lruvec, > +retry: > + lruvec = folio_lruvec_tryrelock_irqsave(folio, lruvec, > &flags); > + if (!lruvec) { > + cond_resched(); > + goto retry; > + } > + > if (prev_lruvec != lruvec) > lock_batch = 0; > > -- > 2.31.1 -- Michal Hocko SUSE Labs