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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DF56CDB47E for ; Thu, 12 Oct 2023 13:09:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344016AbjJLNJ3 (ORCPT ); Thu, 12 Oct 2023 09:09:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343765AbjJLNJ1 (ORCPT ); Thu, 12 Oct 2023 09:09:27 -0400 Received: from outbound-smtp60.blacknight.com (outbound-smtp60.blacknight.com [46.22.136.244]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D11DE91 for ; Thu, 12 Oct 2023 06:09:25 -0700 (PDT) Received: from mail.blacknight.com (pemlinmail05.blacknight.ie [81.17.254.26]) by outbound-smtp60.blacknight.com (Postfix) with ESMTPS id 64163FB149 for ; Thu, 12 Oct 2023 14:09:24 +0100 (IST) Received: (qmail 469 invoked from network); 12 Oct 2023 13:09:24 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.197.19]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 12 Oct 2023 13:09:23 -0000 Date: Thu, 12 Oct 2023 14:09:21 +0100 From: Mel Gorman To: Andrew Morton Cc: Huang Ying , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Arjan Van De Ven , Vlastimil Babka , David Hildenbrand , Johannes Weiner , Dave Hansen , Michal Hocko , Pavel Tatashin , Matthew Wilcox , Christoph Lameter Subject: Re: [PATCH 01/10] mm, pcp: avoid to drain PCP when process exit Message-ID: <20231012130921.mkcftgq4njnpl3qy@techsingularity.net> References: <20230920061856.257597-1-ying.huang@intel.com> <20230920061856.257597-2-ying.huang@intel.com> <20231011124610.4punxroovolyvmgr@techsingularity.net> <20231011101617.2f814633defaa13e77308d9b@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20231011101617.2f814633defaa13e77308d9b@linux-foundation.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 11, 2023 at 10:16:17AM -0700, Andrew Morton wrote: > On Wed, 11 Oct 2023 13:46:10 +0100 Mel Gorman wrote: > > > > --- a/include/linux/mmzone.h > > > +++ b/include/linux/mmzone.h > > > @@ -676,12 +676,15 @@ enum zone_watermarks { > > > #define high_wmark_pages(z) (z->_watermark[WMARK_HIGH] + z->watermark_boost) > > > #define wmark_pages(z, i) (z->_watermark[i] + z->watermark_boost) > > > > > > +#define PCPF_PREV_FREE_HIGH_ORDER 0x01 > > > + > > > > The meaning of the flag and its intent should have been documented. > > I need to rebase mm-stable for other reasons. So let's please > decide (soon) whether Mel's review comments can be addressed > via add-on patches or whether I should drop this version of this > series altogether, during that rebase. The cache slice calculation is the only change I think may deserve a respin as it may have a material impact on the performance figures if the "size_data" value changes by too much. Huang, what do you think and how long do you think it would take to update the performance figures? As it may require multiple tests for each patch in the series, I would also be ok with a follow-on patch like "mm: page_alloc: Simply cache size estimation for PCP tuning" that documents the limitation of summing the unified caches and the impact, if any, on performance. It makes for a messy history *but* it would also record the reasons why summing hierarchies is not necessarily the best approach which also has value. I think patch 9 should be dropped as it has no impact on headline performance while adding a relatively tricky heuristic that updates within a fast path. Again, I'd like to give Huang a chance to respond and to evaluate if it materially impacts patch 10 -- I don't think it does but I didn't think very hard about it. Even if patch 9+10 had to be dropped, it would not take much from the overall value of the series. Comments and documentation alone are not grounds for pulling the series but I hope they do get addressed in follow-on patches. I think requiring them for accepting the series is unfair even if the only reason is I took too long to review. -- Mel Gorman SUSE Labs