From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756398AbYF3Dm4 (ORCPT ); Sun, 29 Jun 2008 23:42:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752029AbYF3Dms (ORCPT ); Sun, 29 Jun 2008 23:42:48 -0400 Received: from e28smtp04.in.ibm.com ([59.145.155.4]:41434 "EHLO e28esmtp04.in.ibm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751941AbYF3Dms (ORCPT ); Sun, 29 Jun 2008 23:42:48 -0400 Message-ID: <48685640.5080408@linux.vnet.ibm.com> Date: Mon, 30 Jun 2008 09:12:56 +0530 From: Balbir Singh Reply-To: balbir@linux.vnet.ibm.com Organization: IBM User-Agent: Thunderbird 2.0.0.14 (X11/20080505) MIME-Version: 1.0 To: Paul Menage CC: Andrew Morton , YAMAMOTO Takashi , linux-kernel@vger.kernel.org, linux-mm@kvack.org, KAMEZAWA Hiroyuki Subject: Re: [RFC 5/5] Memory controller soft limit reclaim on contention References: <20080627151808.31664.36047.sendpatchset@balbir-laptop> <20080627151906.31664.7247.sendpatchset@balbir-laptop> <6599ad830806270909w6a2c26d8mcf406856c06c5da@mail.gmail.com> In-Reply-To: <6599ad830806270909w6a2c26d8mcf406856c06c5da@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paul Menage wrote: > On Fri, Jun 27, 2008 at 8:19 AM, Balbir Singh wrote: >> +/* >> + * Create a heap of memory controller structures. The heap is reverse >> + * sorted by size. This heap is used for implementing soft limits. Our >> + * current heap implementation does not allow dynamic heap updates, but >> + * eventually, the costliest controller (over it's soft limit should > > it's -> its > Yes >> + old_mem = heap_insert(&mem_cgroup_heap, mem, >> + HEAP_REP_LEAF); >> + mem->on_heap = 1; >> + if (old_mem) >> + old_mem->on_heap = 0; > > Maybe a comment here that mem might == old_mem? > >> + * When the soft limit is exceeded, look through the heap and start >> + * reclaiming from all groups over thier soft limit > > thier -> their > Will fix >> + if (!res_counter_check_under_soft_limit(&mem->res)) { >> + /* >> + * The current task might already be over it's soft >> + * limit and trying to aggressively grow. We check to >> + * see if it the memory group associated with the >> + * current task is on the heap when the current group >> + * is over it's soft limit. If not, we add it >> + */ >> + if (!mem->on_heap) { >> + struct mem_cgroup *old_mem; >> + >> + old_mem = heap_insert(&mem_cgroup_heap, mem, >> + HEAP_REP_LEAF); >> + mem->on_heap = 1; >> + if (old_mem) >> + old_mem->on_heap = 0; >> + } >> + } > > This and the other similar code for adding to the heap should be > refactored into a separate function. > OK, I can look into that. >> +static int mem_cgroup_compare_soft_limits(void *p1, void *p2) >> +{ >> + struct mem_cgroup *mem1 = (struct mem_cgroup *)p1; >> + struct mem_cgroup *mem2 = (struct mem_cgroup *)p2; >> + unsigned long long delta1, delta2; >> + >> + delta1 = res_counter_soft_limit_delta(&mem1->res); >> + delta2 = res_counter_soft_limit_delta(&mem2->res); >> + >> + return delta1 > delta2; >> +} > > This isn't a valid comparator, since it isn't a constant function of > its two input pointers - calling mem_cgroup_compare_soft_limits(m1, > m2) can give different results at different times. So your heap > invariant will become invalid over time. > > I think if you want to do this, you're going to need to periodically > take a snapshot of each cgroup's excess and use that snapshot in the > comparator; whenever you update the snapshots, you'll need to restore > the heap invariant. > I'll fix it by taking snapshots only before inserting an element into the heap (I think I responded to this one in another email, but missed out on the typos). -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL