From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f173.google.com (mail-wi0-f173.google.com [209.85.212.173]) by kanga.kvack.org (Postfix) with ESMTP id 5D3186B0253 for ; Mon, 24 Aug 2015 16:53:41 -0400 (EDT) Received: by wicja10 with SMTP id ja10so83001728wic.1 for ; Mon, 24 Aug 2015 13:53:40 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id cj8si34520451wjc.164.2015.08.24.13.53.38 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 24 Aug 2015 13:53:39 -0700 (PDT) Subject: Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled References: <1440418191-10894-1-git-send-email-mgorman@techsingularity.net> <1440418191-10894-5-git-send-email-mgorman@techsingularity.net> <55DB1015.4080103@suse.cz> <20150824131616.GK12432@techsingularity.net> From: Vlastimil Babka Message-ID: <55DB8451.4000102@suse.cz> Date: Mon, 24 Aug 2015 22:53:37 +0200 MIME-Version: 1.0 In-Reply-To: <20150824131616.GK12432@techsingularity.net> Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Andrew Morton , Johannes Weiner , Rik van Riel , David Rientjes , Joonsoo Kim , Michal Hocko , Linux-MM , LKML On 24.8.2015 15:16, Mel Gorman wrote: >>> >>> return read_seqcount_retry(¤t->mems_allowed_seq, seq); >>> @@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask) >>> >>> #else /* !CONFIG_CPUSETS */ >>> >>> -static inline bool cpusets_enabled(void) { return false; } >>> +static inline bool cpusets_mems_enabled(void) { return false; } >>> >>> static inline int cpuset_init(void) { return 0; } >>> static inline void cpuset_init_smp(void) {} >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index 62ae28d8ae8d..2c1c3bf54d15 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, >>> if (IS_ENABLED(CONFIG_NUMA) && zlc_active && >>> !zlc_zone_worth_trying(zonelist, z, allowednodes)) >>> continue; >>> - if (cpusets_enabled() && >>> + if (cpusets_mems_enabled() && >>> (alloc_flags & ALLOC_CPUSET) && >>> !cpuset_zone_allowed(zone, gfp_mask)) >>> continue; >> >> Here the benefits are less clear. I guess cpuset_zone_allowed() is >> potentially costly... >> >> Heck, shouldn't we just start the static key on -1 (if possible), so that >> it's enabled only when there's 2+ cpusets? Hm wait a minute, that's what already happens: static inline int nr_cpusets(void) { /* jump label reference count + the top-level cpuset */ return static_key_count(&cpusets_enabled_key) + 1; } I.e. if there's only the root cpuset, static key is disabled, so I think this patch is moot after all? > It's overkill for the amount of benefit. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org