From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f182.google.com (mail-pd0-f182.google.com [209.85.192.182]) by kanga.kvack.org (Postfix) with ESMTP id 51AFB900002 for ; Thu, 12 Jun 2014 02:49:58 -0400 (EDT) Received: by mail-pd0-f182.google.com with SMTP id y13so653310pdi.13 for ; Wed, 11 Jun 2014 23:49:57 -0700 (PDT) Received: from lgemrelse6q.lge.com (LGEMRELSE6Q.lge.com. [156.147.1.121]) by mx.google.com with ESMTP id tf3si101423pac.14.2014.06.11.23.49.55 for ; Wed, 11 Jun 2014 23:49:57 -0700 (PDT) Date: Thu, 12 Jun 2014 15:53:45 +0900 From: Joonsoo Kim Subject: Re: [PATCH -mm v2 8/8] slab: make dead memcg caches discard free slabs immediately Message-ID: <20140612065345.GD19918@js1304-P5Q-DELUXE> References: <27a202c6084d6bb19cc3e417793f05104b908ded.1402060096.git.vdavydov@parallels.com> <20140610074317.GE19036@js1304-P5Q-DELUXE> <20140610100313.GA6293@esperanza> <20140610151830.GA8692@esperanza> <20140611212431.GA16589@esperanza> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140611212431.GA16589@esperanza> Sender: owner-linux-mm@kvack.org List-ID: To: Vladimir Davydov Cc: Christoph Lameter , akpm@linux-foundation.org, rientjes@google.com, penberg@kernel.org, hannes@cmpxchg.org, mhocko@suse.cz, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Thu, Jun 12, 2014 at 01:24:34AM +0400, Vladimir Davydov wrote: > On Tue, Jun 10, 2014 at 07:18:34PM +0400, Vladimir Davydov wrote: > > On Tue, Jun 10, 2014 at 09:26:19AM -0500, Christoph Lameter wrote: > > > On Tue, 10 Jun 2014, Vladimir Davydov wrote: > > > > > > > Frankly, I incline to shrinking dead SLAB caches periodically from > > > > cache_reap too, because it looks neater and less intrusive to me. Also > > > > it has zero performance impact, which is nice. > > > > > > > > However, Christoph proposed to disable per cpu arrays for dead caches, > > > > similarly to SLUB, and I decided to give it a try, just to see the end > > > > code we'd have with it. > > > > > > > > I'm still not quite sure which way we should choose though... > > > > > > Which one is cleaner? > > > > To shrink dead caches aggressively, we only need to modify cache_reap > > (see https://lkml.org/lkml/2014/5/30/271). > > Hmm, reap_alien, which is called from cache_reap to shrink per node > alien object arrays, only processes one node at a time. That means with > the patch I gave a link to above it will take up to > (REAPTIMEOUT_AC*nr_online_nodes) seconds to destroy a virtually empty > dead cache, which may be quite long on large machines. Of course, we can > make reap_alien walk over all alien caches of the current node, but that > will probably hurt performance... Hmm, maybe we have a few of objects on other node, doesn't it? BTW, I have a question about cache_reap(). If there are many kmemcg users, we would have a lot of slab caches and just to traverse slab cache list could take some times. Is it no problem? Thanks. -- 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