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 502EFC43441 for ; Tue, 9 Oct 2018 23:03:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0BA6D2087D for ; Tue, 9 Oct 2018 23:03:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0BA6D2087D 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 S1726741AbeJJGXI (ORCPT ); Wed, 10 Oct 2018 02:23:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46374 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725827AbeJJGXI (ORCPT ); Wed, 10 Oct 2018 02:23:08 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E14D2307D861; Tue, 9 Oct 2018 23:03:53 +0000 (UTC) Received: from sky.random (ovpn-120-22.rdu2.redhat.com [10.10.120.22]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AD2F27C81E; Tue, 9 Oct 2018 23:03:53 +0000 (UTC) Date: Tue, 9 Oct 2018 19:03:52 -0400 From: Andrea Arcangeli To: Michal Hocko Cc: Mel Gorman , David Rientjes , Andrew Morton , 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: <20181009230352.GE9307@redhat.com> References: <20180925120326.24392-2-mhocko@kernel.org> <20181005073854.GB6931@suse.de> <20181005232155.GA2298@redhat.com> <20181009094825.GC6931@suse.de> <20181009122745.GN8528@dhcp22.suse.cz> <20181009130034.GD6931@suse.de> <20181009142510.GU8528@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181009142510.GU8528@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.48]); Tue, 09 Oct 2018 23:03:54 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 09, 2018 at 04:25:10PM +0200, Michal Hocko wrote: > On Tue 09-10-18 14:00:34, Mel Gorman wrote: > > On Tue, Oct 09, 2018 at 02:27:45PM +0200, Michal Hocko wrote: > > > [Sorry for being slow in responding but I was mostly offline last few > > > days] > > > > > > On Tue 09-10-18 10:48:25, Mel Gorman wrote: > > > [...] > > > > This goes back to my point that the MADV_HUGEPAGE hint should not make > > > > promises about locality and that introducing MADV_LOCAL for specialised > > > > libraries may be more appropriate with the initial semantic being how it > > > > treats MADV_HUGEPAGE regions. > > > > > > I agree with your other points and not going to repeat them. I am not > > > sure madvise s the best API for the purpose though. We are talking about > > > memory policy here and there is an existing api for that so I would > > > _prefer_ to reuse it for this purpose. > > > > > > > I flip-flopped on that one in my head multiple times on the basis of > > how strict it should be. Memory policies tend to be black or white -- > > bind here, interleave there, etc. It wasn't clear to me what the best > > policy would be to describe "allocate local as best as you can but allow > > fallbacks if necessary". MPOL_PREFERRED is not black and white. In fact I asked David earlier if MPOL_PREFERRED could check if it would already be a good fit for this. Still the point is it requires privilege (and for a good reason). > I was thinking about MPOL_NODE_PROXIMITY with the following semantic: > - try hard to allocate from a local or very close numa node(s) even when > that requires expensive operations like the memory reclaim/compaction > before falling back to other more distant numa nodes. If MPOL_PREFERRED can't work something like this could be added. I think "madvise vs mbind" is more an issue of "no-permission vs permission" required. And if the processes ends up swapping out all other process with their memory already allocated in the node, I think some permission is correct to be required, in which case an mbind looks a better fit. MPOL_PREFERRED also looks a first candidate for investigation as it's already not black and white and allows spillover and may already do the right thing in fact if set on top of MADV_HUGEPAGE. Thanks, Andrea