From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id 5472B6B00BF for ; Mon, 2 Mar 2009 00:34:10 -0500 (EST) Received: from m1.gw.fujitsu.co.jp ([10.0.50.71]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n225Y7m7006394 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Mon, 2 Mar 2009 14:34:07 +0900 Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 5742945DD74 for ; Mon, 2 Mar 2009 14:34:07 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 0DF4045DD70 for ; Mon, 2 Mar 2009 14:34:07 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 1FF1BE08004 for ; Mon, 2 Mar 2009 14:34:07 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id B986C1DB803C for ; Mon, 2 Mar 2009 14:34:06 +0900 (JST) Date: Mon, 2 Mar 2009 14:32:50 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH 0/4] Memory controller soft limit patches (v3) Message-Id: <20090302143250.f47758f9.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090302044043.GC11421@balbir.in.ibm.com> References: <20090301062959.31557.31079.sendpatchset@localhost.localdomain> <20090302092404.1439d2a6.kamezawa.hiroyu@jp.fujitsu.com> <20090302044043.GC11421@balbir.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: balbir@linux.vnet.ibm.com Cc: linux-mm@kvack.org, Sudhir Kumar , YAMAMOTO Takashi , Bharata B Rao , Paul Menage , lizf@cn.fujitsu.com, linux-kernel@vger.kernel.org, KOSAKI Motohiro , David Rientjes , Pavel Emelianov , Dhaval Giani , Rik van Riel , Andrew Morton List-ID: On Mon, 2 Mar 2009 10:10:43 +0530 Balbir Singh wrote: > * KAMEZAWA Hiroyuki [2009-03-02 09:24:04]: > > > On Sun, 01 Mar 2009 11:59:59 +0530 > > Balbir Singh wrote: > > > > > > > > From: Balbir Singh > > > > At first, it's said "When cgroup people adds something, the kernel gets slow". > > This is my start point of reviewing. Below is comments to this version of patch. > > > > 1. I think it's bad to add more hooks to res_counter. It's enough slow to give up > > adding more fancy things.. > > res_counters was desgined to be extensible, why is adding anything to > it going to make it slow, unless we turn on soft_limits? > You inserted new "if" logic in the core loop. (What I want to say here is not that this is definitely bad but that "isn't there any alternatives which is less overhead.) > > > > 2. please avoid to add hooks to hot-path. In your patch, especially a hook to > > mem_cgroup_uncharge_common() is annoying me. > > If soft limits are not enabled, the function does a small check and > leaves. > &soft_fail_res is passed always even if memory.soft_limit==ULONG_MAX res_counter_soft_limit_excess() adds one more function call and spinlock, and irq-off. > > > > 3. please avoid to use global spinlock more. > > no lock is best. mutex is better, maybe. > > > > No lock to update a tree which is update concurrently? > Using tree/sort itself is nonsense, I believe. > > 4. RB-tree seems broken. Following is example. (please note you do all ops > > in lazy manner (once in HZ/4.) > > > > i). while running, the tree is constructed as following > > > > R R=exceed=300M > > / \ > > A B A=exceed=200M B=exceed=400M > > ii) A process B exits, but and usage goes down. > > That is why we have the hook in uncharge. Even if we update and the > usage goes down, the tree is ordered by usage_in_excess which is > updated only when the tree is updated. So what you show below does not > occur. I think I should document the design better. > time_check==true. So, update-tree at uncharge() only happens once in HZ/4 == @@ -1422,6 +1520,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) mz = page_cgroup_zoneinfo(pc); unlock_page_cgroup(pc); + mem_cgroup_check_and_update_tree(mem, true); /* at swapout, this memcg will be accessed to record to swap */ if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT) css_put(&mem->css); == Then, not-sorted RB-tree can be there. BTW, time_after(jiffies, 0) is buggy (see definition). If you want make this true always, time_after(jiffies, jiffies +1) Thanks, -Kame -- 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