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=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 C26D3C4363A for ; Tue, 20 Oct 2020 20:33:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 66C4A2225F for ; Tue, 20 Oct 2020 20:33:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2438430AbgJTUde (ORCPT ); Tue, 20 Oct 2020 16:33:34 -0400 Received: from mx2.suse.de ([195.135.220.15]:47494 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731214AbgJTUde (ORCPT ); Tue, 20 Oct 2020 16:33:34 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2A927ACDB; Tue, 20 Oct 2020 20:33:33 +0000 (UTC) Date: Tue, 20 Oct 2020 21:33:31 +0100 From: Mel Gorman To: Johannes Weiner Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH] mm: don't wake kswapd prematurely when watermark boosting is disabled Message-ID: <20201020203331.GB32041@suse.de> References: <20201020175833.397286-1-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20201020175833.397286-1-hannes@cmpxchg.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 20, 2020 at 01:58:33PM -0400, Johannes Weiner wrote: > On 2-node NUMA hosts we see bursts of kswapd reclaim and subsequent > pressure spikes and stalls from cache refaults while there is plenty > of free memory in the system. > > Usually, kswapd is woken up when all eligible nodes in an allocation > are full. But the code related to watermark boosting can wake kswapd > on one full node while the other one is mostly empty. This may be > justified to fight fragmentation, but is currently unconditionally > done whether watermark boosting is occurring or not. > > In our case, many of our workloads' throughput scales with available > memory, and pure utilization is a more tangible concern than trends > around longer-term fragmentation. As a result we generally disable > watermark boosting. > > Wake kswapd only woken when watermark boosting is requested. > > Signed-off-by: Johannes Weiner This makes sense to the extent that I would support adding Fixes: 1c30844d2dfe ("mm: reclaim small amounts of memory when an external fragmentation event occurs") With or without that; Acked-by: Mel Gorman -- Mel Gorman SUSE Labs