Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753956AbZFEBKb (ORCPT ); Thu, 4 Jun 2009 21:10:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752204AbZFEBKY (ORCPT ); Thu, 4 Jun 2009 21:10:24 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:39050 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752138AbZFEBKY (ORCPT ); Thu, 4 Jun 2009 21:10:24 -0400 Date: Fri, 5 Jun 2009 09:10:19 +0800 From: Balbir Singh To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "nishimura@mxp.nes.nec.co.jp" Subject: Re: [PATCH] remove memory.limit v.s. memsw.limit comparison. Message-ID: <20090605011019.GG7504@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20090604141043.9a1064fd.kamezawa.hiroyu@jp.fujitsu.com> <20090604123625.GE7504@balbir.in.ibm.com> <0921392c77890fc84fa69653ae4f31d9.squirrel@webmail-b.css.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <0921392c77890fc84fa69653ae4f31d9.squirrel@webmail-b.css.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2753 Lines: 71 * KAMEZAWA Hiroyuki [2009-06-05 00:45:03]: > Balbir Singh wrote: > > * KAMEZAWA Hiroyuki [2009-06-04 > > 14:10:43]: > > > >> From: KAMEZAWA Hiroyuki > >> > >> Removes memory.limit < memsw.limit at setting limit check completely. > >> > >> The limitation "memory.limit <= memsw.limit" was added just because > >> it seems sane ...if memory.limit > memsw.limit, only memsw.limit works. > >> > >> But To implement this limitation, we needed to use private mutex and > >> make > >> the code a bit complated. > >> As Nishimura pointed out, in real world, there are people who only want > >> to use memsw.limit. > >> > >> Then, this patch removes the check. user-land library or middleware can > >> check > >> this in userland easily if this really concerns. > >> > >> And this is a good change to charge-and-reclaim. > >> > >> Now, memory.limit is always checked before memsw.limit > >> and it may do swap-out. But, if memory.limit == memsw.limit, swap-out is > >> finally no help and hits memsw.limit again. So, let's allow the > >> condition > >> memory.limit > memsw.limit. Then we can skip unnecesary swap-out. > >> > >> Signed-off-by: KAMEZAWA Hiroyuki > >> --- > > > > There is one other option, we could set memory.limit_in_bytes == > > memory.memsw.limit_in_bytes provided it is set to LONG_LONG_MAX. I am > > not convinced that we should allow memsw.limit_in_bytes to be less > > that limit_in_bytes, it will create confusion and the API is already > > exposed. > > > Ahhhh, I get your point. > if memory.memsw.limit_in_bytes < memory.limit_in_bytes, no swap will > be used bacause currnet try_to_free_pages() for memcg skips swap-out. > Then, only global-LRU will use swap. > This behavior is not easy to understand. > > Sorry, I don't push this patch as this is. But adding documentation about > "What happens when you set memory.limit == memsw.limit" will be necessary. > > ...maybe give all jobs to user-land and keep the kernel as it is now > is a good choice. Yes, probably and with libcgroup and configuration, defaults should not be hard to setup. Worst case we can use a script to setup both the values. > > BTW, I'd like to avoid useless swap-out in memory.limit == memsw.limit case. > If someone has good idea, please :( > Are you seeing swap even with memory.limit == memory.memsw.limit? Only global pressure should cause swapout, no? -- Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/