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_HELO_NONE,SPF_PASS,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 E9383C47E49 for ; Tue, 22 Oct 2019 13:49:54 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B0F6121872 for ; Tue, 22 Oct 2019 13:49:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B0F6121872 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 49D0B6B000A; Tue, 22 Oct 2019 09:49:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 426886B000C; Tue, 22 Oct 2019 09:49:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 314A36B000D; Tue, 22 Oct 2019 09:49:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0157.hostedemail.com [216.40.44.157]) by kanga.kvack.org (Postfix) with ESMTP id 0928D6B000A for ; Tue, 22 Oct 2019 09:49:54 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id ADFD4181AF5D3 for ; Tue, 22 Oct 2019 13:49:53 +0000 (UTC) X-FDA: 76071553866.08.wash58_1c2677f9edf48 X-HE-Tag: wash58_1c2677f9edf48 X-Filterd-Recvd-Size: 3234 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf30.hostedemail.com (Postfix) with ESMTP for ; Tue, 22 Oct 2019 13:49:53 +0000 (UTC) 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 6D6D6AFA8; Tue, 22 Oct 2019 13:49:51 +0000 (UTC) Date: Tue, 22 Oct 2019 15:49:50 +0200 From: Michal Hocko To: Dave Hansen Cc: Dave Hansen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, dan.j.williams@intel.com Subject: Re: [PATCH 0/4] [RFC] Migrate Pages in lieu of discard Message-ID: <20191022134950.GQ9379@dhcp22.suse.cz> References: <20191016221148.F9CCD155@viggo.jf.intel.com> <20191018074411.GC5017@dhcp22.suse.cz> <0b05c135-4762-e745-5289-58ee84cc8c3e@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0b05c135-4762-e745-5289-58ee84cc8c3e@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri 18-10-19 07:54:20, Dave Hansen wrote: > On 10/18/19 12:44 AM, Michal Hocko wrote: > > How does this compare to > > http://lkml.kernel.org/r/1560468577-101178-1-git-send-email-yang.shi@linux.alibaba.com > > It's a _bit_ more tied to persistent memory and it appears a bit more > tied to two tiers rather something arbitrarily deep. They're pretty > similar conceptually although there are quite a few differences. > > For instance, what I posted has a static mapping for the migration path. > If node A is in reclaim, we always try to allocate pages on node B. > There are no restrictions on what those nodes can be. In Yang Shi's > apporach, there's a dynamic search for a target migration node on each > migration that follows the normal alloc fallback path. This ends up > making migration nodes special. As we have discussed at LSFMM this year and there seemed to be a goog consensus on that, the resulting implementation should be as pmem neutral as possible. After all node migration mode sounds like a reasonable feature even without pmem. So I would be more inclined to the normal alloc fallback path rather than a very specific and static migration fallback path. If that turns out impractical then sure let's come up with something more specific but I think there is quite a long route there because we do not really have much of an experience with this so far. > There are also some different choices that are pretty arbitrary. For > instance, when you allocation a migration target page, should you cause > memory pressure on the target? Those are details to really sort out and they require some experimentation to. > To be honest, though, I don't see anything fatally flawed with it. It's > probably a useful exercise to factor out the common bits from the two > sets and see what we can agree on being absolutely necessary. Makes sense. What would that be? Is there a real consensus on having the new node_reclaim mode to be the configuration mechanism? Do we want to support generic NUMA without any PMEM in place as well for starter? Thanks! -- Michal Hocko SUSE Labs