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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 2329CC5ACCC for ; Thu, 18 Oct 2018 08:16:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D653121479 for ; Thu, 18 Oct 2018 08:16:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D653121479 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727722AbeJRQPt (ORCPT ); Thu, 18 Oct 2018 12:15:49 -0400 Received: from mx2.suse.de ([195.135.220.15]:44914 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727376AbeJRQPt (ORCPT ); Thu, 18 Oct 2018 12:15:49 -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 488B5AFD1; Thu, 18 Oct 2018 08:15:57 +0000 (UTC) Date: Thu, 18 Oct 2018 10:15:52 +0200 From: Michal Hocko To: Chris Wilson Cc: Kuo-Hsin Yang , linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org, akpm@linux-foundation.org, peterz@infradead.org, dave.hansen@intel.com, corbet@lwn.net, hughd@google.com, joonas.lahtinen@linux.intel.com, marcheu@chromium.org, hoegsberg@chromium.org Subject: Re: [PATCH 2/2] drm/i915: Mark pinned shmemfs pages as unevictable Message-ID: <20181018081552.GZ18839@dhcp22.suse.cz> References: <20181016174300.197906-1-vovoy@chromium.org> <20181016174300.197906-3-vovoy@chromium.org> <20181016182155.GW18839@dhcp22.suse.cz> <153971466599.22931.16793398326492316920@skylake-alporthouse-com> <153984580501.19935.11456945882099910977@skylake-alporthouse-com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <153984580501.19935.11456945882099910977@skylake-alporthouse-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 Thu 18-10-18 07:56:45, Chris Wilson wrote: > Quoting Chris Wilson (2018-10-16 19:31:06) > > Fwiw, the shmem_unlock_mapping() call feels quite expensive, almost > > nullifying the advantage gained from not walking the lists in reclaim. > > I'll have better numbers in a couple of days. > > Using a test ("igt/benchmarks/gem_syslatency -t 120 -b -m" on kbl) > consisting of cycletest with a background load of trying to allocate + > populate 2MiB (to hit thp) while catting all files to /dev/null, the > result of using mapping_set_unevictable is mixed. I haven't really read through your report completely yet but I wanted to point out that the above test scenario is unlikely show the real effect of the LRU scanning overhead because shmem pages do live on the anonymous LRU list. With a plenty of file page cache available we do not even scan anonymous LRU lists. You would have to generate a swapout workload to test this properly. On the other hand if mapping_set_unevictable has really a measurably bad performance impact then this is probably not worth much because most workloads are swap modest. -- Michal Hocko SUSE Labs