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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 035C4C433EF for ; Wed, 24 Nov 2021 16:32:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348994AbhKXQfL (ORCPT ); Wed, 24 Nov 2021 11:35:11 -0500 Received: from smtp-out1.suse.de ([195.135.220.28]:54254 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348973AbhKXQfI (ORCPT ); Wed, 24 Nov 2021 11:35:08 -0500 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> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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