From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx188.postini.com [74.125.245.188]) by kanga.kvack.org (Postfix) with SMTP id 81EC86B004A for ; Tue, 28 Feb 2012 17:45:09 -0500 (EST) Date: Tue, 28 Feb 2012 14:45:07 -0800 From: Andrew Morton Subject: Re: [PATCH 4/9] memcg: dirty page accounting support routines Message-Id: <20120228144507.acd70d1e.akpm@linux-foundation.org> In-Reply-To: <20120228144747.124608935@intel.com> References: <20120228140022.614718843@intel.com> <20120228144747.124608935@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Fengguang Wu Cc: Greg Thelen , Jan Kara , Ying Han , "hannes@cmpxchg.org" , KAMEZAWA Hiroyuki , Rik van Riel , Linux Memory Management List , LKML On Tue, 28 Feb 2012 22:00:26 +0800 Fengguang Wu wrote: > From: Greg Thelen > > Added memcg dirty page accounting support routines. These routines are > used by later changes to provide memcg aware writeback and dirty page > limiting. A mem_cgroup_dirty_info() tracepoint is is also included to > allow for easier understanding of memcg writeback operation. > > ... > > +/* > + * Return the number of additional pages that the @memcg cgroup could allocate. > + * If use_hierarchy is set, then this involves checking parent mem cgroups to > + * find the cgroup with the smallest free space. > + */ Comment needs revisting - use_hierarchy does not exist. > +static unsigned long > +mem_cgroup_hierarchical_free_pages(struct mem_cgroup *memcg) > +{ > + u64 free; > + unsigned long min_free; > + > + min_free = global_page_state(NR_FREE_PAGES); > + > + while (memcg) { > + free = mem_cgroup_margin(memcg); > + min_free = min_t(u64, min_free, free); > + memcg = parent_mem_cgroup(memcg); > + } > + > + return min_free; > +} > + > +/* > + * mem_cgroup_page_stat() - get memory cgroup file cache statistics > + * @memcg: memory cgroup to query > + * @item: memory statistic item exported to the kernel > + * > + * Return the accounted statistic value. > + */ > +unsigned long mem_cgroup_page_stat(struct mem_cgroup *memcg, > + enum mem_cgroup_page_stat_item item) > +{ > + struct mem_cgroup *iter; > + s64 value; > + > + /* > + * If we're looking for dirtyable pages we need to evaluate free pages > + * depending on the limit and usage of the parents first of all. > + */ > + if (item == MEMCG_NR_DIRTYABLE_PAGES) > + value = mem_cgroup_hierarchical_free_pages(memcg); > + else > + value = 0; > + > + /* > + * Recursively evaluate page statistics against all cgroup under > + * hierarchy tree > + */ > + for_each_mem_cgroup_tree(iter, memcg) > + value += mem_cgroup_local_page_stat(iter, item); What's the locking rule for for_each_mem_cgroup_tree()? It's unobvious from the code and isn't documented? > + /* > + * Summing of unlocked per-cpu counters is racy and may yield a slightly > + * negative value. Zero is the only sensible value in such cases. > + */ > + if (unlikely(value < 0)) > + value = 0; > + > + return value; > +} > + > > ... > -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org