From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from spaceape24.eur.corp.google.com (spaceape24.eur.corp.google.com [172.28.16.76]) by smtp-out.google.com with ESMTP id m5RG9CUv023084 for ; Fri, 27 Jun 2008 17:09:12 +0100 Received: from an-out-0708.google.com (andd30.prod.google.com [10.100.30.30]) by spaceape24.eur.corp.google.com with ESMTP id m5RG9BJG012161 for ; Fri, 27 Jun 2008 17:09:11 +0100 Received: by an-out-0708.google.com with SMTP id d30so114663and.30 for ; Fri, 27 Jun 2008 09:09:11 -0700 (PDT) Message-ID: <6599ad830806270909w6a2c26d8mcf406856c06c5da@mail.gmail.com> Date: Fri, 27 Jun 2008 09:09:10 -0700 From: "Paul Menage" Subject: Re: [RFC 5/5] Memory controller soft limit reclaim on contention In-Reply-To: <20080627151906.31664.7247.sendpatchset@balbir-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080627151808.31664.36047.sendpatchset@balbir-laptop> <20080627151906.31664.7247.sendpatchset@balbir-laptop> Sender: owner-linux-mm@kvack.org Return-Path: To: Balbir Singh Cc: Andrew Morton , YAMAMOTO Takashi , linux-kernel@vger.kernel.org, linux-mm@kvack.org, KAMEZAWA Hiroyuki List-ID: 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 > + 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 > + 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. > > +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. Paul -- 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