From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 5 Jul 2008 15:11:46 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH] memcg: handle shmem's swap cache (Was 2.6.26-rc8-mm1 Message-Id: <20080705151146.206071a4.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <486F0976.7010104@linux.vnet.ibm.com> References: <20080703020236.adaa51fa.akpm@linux-foundation.org> <20080704180913.bb1a3fc6.kamezawa.hiroyu@jp.fujitsu.com> <486F0976.7010104@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: balbir@linux.vnet.ibm.com Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "hugh@veritas.com" , "nishimura@mxp.nes.nec.co.jp" , "yamamoto@valinux.co.jp" List-ID: On Sat, 05 Jul 2008 11:11:10 +0530 Balbir Singh wrote: > KAMEZAWA Hiroyuki wrote: > > My swapcache accounting under memcg patch failed to catch tmpfs(shmem)'s one. > > Can I test this under -mm tree ? > > (If -mm is busy, I'm not in hurry.) > > This patch works well in my box. > > = > > SwapCache handling fix. > > > > shmem's swapcache behavior is a little different from anonymous's one and > > memcg failed to handle it. This patch tries to fix it. > > > > After this: > > > > Any page marked as SwapCache is not uncharged. (delelte_from_swap_cache() > > delete the SwapCache flag.) > > > > To check a shmem-page-cache is alive or not we use > > page->mapping && !PageAnon(page) instead of > > pc->flags & PAGE_CGROUP_FLAG_CACHE. > > > > Signed-off-by: KAMEZAWA Hiroyuki > > Though I am not opposed to this, I do sit up and think if keeping the reference > count around could avoid this complexity and from my point, the maintenance > overhead of this logic/code (I fear there might be more special cases :( ) yes, to me. but we have to fix.. But I don't like old code's refcnt handling which does - increment - does this increment was really neccesary ? No? ok, decrement it again. This was much more complex to me than current code. And old ones will needs the check at treating swap-cache. (it couldn't but if we want) > > The trade-off is complexity versus the overhead of reference counting. > refcnt was also very complex ;) Thanks, -Kame > -- > Warm Regards, > Balbir Singh > Linux Technology Center > IBM, ISTL > -- 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