Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756225AbZFDPpS (ORCPT ); Thu, 4 Jun 2009 11:45:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753330AbZFDPpG (ORCPT ); Thu, 4 Jun 2009 11:45:06 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:37744 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753151AbZFDPpF (ORCPT ); Thu, 4 Jun 2009 11:45:05 -0400 Message-ID: <0921392c77890fc84fa69653ae4f31d9.squirrel@webmail-b.css.fujitsu.com> In-Reply-To: <20090604123625.GE7504@balbir.in.ibm.com> References: <20090604141043.9a1064fd.kamezawa.hiroyu@jp.fujitsu.com> <20090604123625.GE7504@balbir.in.ibm.com> Date: Fri, 5 Jun 2009 00:45:03 +0900 (JST) Subject: Re: [PATCH] remove memory.limit v.s. memsw.limit comparison. From: "KAMEZAWA Hiroyuki" To: balbir@linux.vnet.ibm.com Cc: "KAMEZAWA Hiroyuki" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "nishimura@mxp.nes.nec.co.jp" User-Agent: SquirrelMail/1.4.16 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-2022-jp Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) Importance: Normal Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2310 Lines: 62 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. BTW, I'd like to avoid useless swap-out in memory.limit == memsw.limit case. If someone has good idea, please :( Thanks, -Kame -- 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/