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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 D24CFC5ACC6 for ; Tue, 16 Oct 2018 23:11:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8CFD92147C for ; Tue, 16 Oct 2018 23:11:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8CFD92147C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1727159AbeJQHEb (ORCPT ); Wed, 17 Oct 2018 03:04:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55574 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726703AbeJQHEa (ORCPT ); Wed, 17 Oct 2018 03:04:30 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id F2016308624E; Tue, 16 Oct 2018 23:11:50 +0000 (UTC) Received: from sky.random (ovpn-120-12.rdu2.redhat.com [10.10.120.12]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5C02060490; Tue, 16 Oct 2018 23:11:50 +0000 (UTC) Date: Tue, 16 Oct 2018 19:11:49 -0400 From: Andrea Arcangeli To: Andrew Morton Cc: Mel Gorman , David Rientjes , Michal Hocko , Vlastimil Babka , Andrea Argangeli , Zi Yan , Stefan Priebe - Profihost AG , "Kirill A. Shutemov" , linux-mm@kvack.org, LKML , Stable tree Subject: Re: [PATCH 1/2] mm: thp: relax __GFP_THISNODE for MADV_HUGEPAGE mappings Message-ID: <20181016231149.GJ30832@redhat.com> References: <20181009094825.GC6931@suse.de> <20181009122745.GN8528@dhcp22.suse.cz> <20181009130034.GD6931@suse.de> <20181009142510.GU8528@dhcp22.suse.cz> <20181009230352.GE9307@redhat.com> <20181015154459.e870c30df5c41966ffb4aed8@linux-foundation.org> <20181016074606.GH6931@suse.de> <20181016153715.b40478ff2eebe8d6cf1aead5@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181016153715.b40478ff2eebe8d6cf1aead5@linux-foundation.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Tue, 16 Oct 2018 23:11:51 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Tue, Oct 16, 2018 at 03:37:15PM -0700, Andrew Morton wrote: > we'll still make it into 4.19.1. Am reluctant to merge this while > discussion, testing and possibly more development are ongoing. I think there can be definitely more developments primarily to make the compact deferred logic NUMA aware. Instead of a global deferred logic, we should split it per zone per node so that it backs off exponentially with an higher cap in remote nodes. The current global "backoff" limit will still apply to the "local" zone compaction. Who would like to work on that? However I don't think it's worth waiting for that, because it's not a trivial change. Certainly we can't ship upstream in production with this bug, so if it doesn't get fixed upstream we'll fix it downstream first until the more developments are production ready. This was a severe regression compared to previous kernels that made important workloads unusable and it starts when __GFP_THISNODE was added to THP allocations under MADV_HUGEPAGE. It is not a significant risk to go to the previous behavior before __GFP_THISNODE was added, it worked like that for years. This was simply an optimization to some lucky workloads that can fit in a single node, but it ended up breaking the VM for others that can't possibly fit in a single node, so going back is safe. Thanks, Andrea