From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754897Ab2BULBa (ORCPT ); Tue, 21 Feb 2012 06:01:30 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:37045 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751567Ab2BULB3 (ORCPT ); Tue, 21 Feb 2012 06:01:29 -0500 Message-ID: <4F437985.7060005@openvz.org> Date: Tue, 21 Feb 2012 15:01:25 +0400 From: Konstantin Khlebnikov User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.19) Gecko/20120201 Iceape/2.0.14 MIME-Version: 1.0 To: Johannes Weiner CC: "linux-mm@kvack.org" , Andrew Morton , KAMEZAWA Hiroyuki , "cgroups@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] memcg: rework inactive_ratio logic References: <20120215162442.13588.21790.stgit@zurg> <20120221101825.GA1676@cmpxchg.org> In-Reply-To: <20120221101825.GA1676@cmpxchg.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Johannes Weiner wrote: > On Wed, Feb 15, 2012 at 08:24:42PM +0400, Konstantin Khlebnikov wrote: >> This patch adds mem_cgroup->inactive_ratio calculated from hierarchical memory limit. >> It updated at each limit change before shrinking cgroup to this new limit. >> Ratios for all child cgroups are updated too, because parent limit can affect them. >> Update precedure can be greatly optimized if its performance becomes the problem. >> Inactive ratio for unlimited or huge limit does not matter, because we'll never hit it. >> >> At global reclaim always use global ratio from zone->inactive_ratio. >> At mem-cgroup reclaim use inactive_ratio from target memory cgroup, >> this is cgroup which hit its limit and cause this reclaimer invocation. >> >> Thus, global memory reclaimer will try to keep ratio for all lru lists in zone >> above one mark, this guarantee that total ratio in this zone will be above too. >> Meanwhile mem-cgroup will do the same thing for its lru lists in all zones, and >> for all lru lists in all sub-cgroups in hierarchy. >> >> Also this patch removes some redundant code. >> >> Signed-off-by: Konstantin Khlebnikov > > I don't think we should take the zone ratio when we then proceed to > scan a bunch of LRU lists that could individually be much smaller than > the zone. Especially since the ratio function is not a linear one. > > Otherwise the target ratios can be way too big for small lists, see > the comment above mm/page_alloc.c::calculate_zone_inactive_ratio(). > > Consequently, I also disagree on using sc->target_mem_cgroup. > > This whole mechanism is about balancing one specific pair of inactive > vs. an active list according their size. We shouldn't derive policy > from numbers that are not correlated to this size. Ok, maybe then we can move this inactive_ratio calculation right into inactive_anon_is_low(). Then we can kill precalculated zone->inactive_ratio and calculate it every time, even in non-memcg case, because zone-size also not always correlate with anon lru size. Looks like int_sqrt() is fast enough for this.