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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 BC18EC4740A for ; Tue, 10 Sep 2019 12:11:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8249E2089F for ; Tue, 10 Sep 2019 12:11:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568117494; bh=9t/uxNlMq1chAbSJNg0XPICF3Vb8vlNP48o5k9NwMds=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=AwYA6m2RHmA3SgPIfdrVXb4zZGL0l4DD0ZLN531dmd5OtbT8IAQKCTAFeZN4b26z7 v21u18/Rc6ghISurtjmJyL/+iIxJpWRiX10fjCTanKzhLlNxZL9uApdBMYcLJeH6B7 haaVMMBo/JZ9n1caxQHMP/kaKyX+vPtDgw/iiWQ8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733303AbfIJMLd (ORCPT ); Tue, 10 Sep 2019 08:11:33 -0400 Received: from mx2.suse.de ([195.135.220.15]:36502 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732482AbfIJMLd (ORCPT ); Tue, 10 Sep 2019 08:11:33 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 668EEB150; Tue, 10 Sep 2019 12:11:31 +0000 (UTC) Date: Tue, 10 Sep 2019 14:11:30 +0200 From: Michal Hocko To: Alexander Duyck Cc: David Hildenbrand , Alexander Duyck , virtio-dev@lists.oasis-open.org, kvm@vger.kernel.org, mst@redhat.com, catalin.marinas@arm.com, dave.hansen@intel.com, linux-kernel@vger.kernel.org, willy@infradead.org, linux-mm@kvack.org, akpm@linux-foundation.org, will@kernel.org, linux-arm-kernel@lists.infradead.org, osalvador@suse.de, yang.zhang.wz@gmail.com, pagupta@redhat.com, konrad.wilk@oracle.com, nitesh@redhat.com, riel@surriel.com, lcapitulino@redhat.com, wei.w.wang@intel.com, aarcange@redhat.com, ying.huang@intel.com, pbonzini@redhat.com, dan.j.williams@intel.com, fengguang.wu@intel.com, kirill.shutemov@linux.intel.com Subject: Re: [PATCH v9 1/8] mm: Add per-cpu logic to page shuffling Message-ID: <20190910121130.GU2063@dhcp22.suse.cz> References: <20190907172225.10910.34302.stgit@localhost.localdomain> <20190907172512.10910.74435.stgit@localhost.localdomain> <0df2e5d0-af92-04b4-aa7d-891387874039@redhat.com> <0ca58fea280b51b83e7b42e2087128789bc9448d.camel@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0ca58fea280b51b83e7b42e2087128789bc9448d.camel@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 09-09-19 08:11:36, Alexander Duyck wrote: > On Mon, 2019-09-09 at 10:14 +0200, David Hildenbrand wrote: > > On 07.09.19 19:25, Alexander Duyck wrote: > > > From: Alexander Duyck > > > > > > Change the logic used to generate randomness in the suffle path so that we > > > can avoid cache line bouncing. The previous logic was sharing the offset > > > and entropy word between all CPUs. As such this can result in cache line > > > bouncing and will ultimately hurt performance when enabled. > > > > So, usually we perform such changes if there is real evidence. Do you > > have any such performance numbers to back your claims? > > I'll have to go rerun the test to get the exact numbers. The reason this > came up is that my original test was spanning NUMA nodes and that made > this more expensive as a result since the memory was both not local to the > CPU and was being updated by multiple sockets. What was the pattern of page freeing in your testing? I am wondering because order 0 pages should be prevailing and those usually go via pcp lists so they do not get shuffled unless the batch is full IIRC. -- Michal Hocko SUSE Labs