From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [patch 4/4] mm: memcontrol: remove unnecessary PCG_USED pc->mem_cgroup valid flag Date: Wed, 22 Oct 2014 18:11:40 +0200 Message-ID: <20141022161140.GG30802@dhcp22.suse.cz> References: <1413818532-11042-1-git-send-email-hannes@cmpxchg.org> <1413818532-11042-5-git-send-email-hannes@cmpxchg.org> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <1413818532-11042-5-git-send-email-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Johannes Weiner Cc: Andrew Morton , Hugh Dickins , Vladimir Davydov , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org On Mon 20-10-14 11:22:12, Johannes Weiner wrote: > pc->mem_cgroup had to be left intact after uncharge for the final LRU > removal, and !PCG_USED indicated whether the page was uncharged. But > since 0a31bc97c80c ("mm: memcontrol: rewrite uncharge API") pages are > uncharged after the final LRU removal. Uncharge can simply clear the > pointer and the PCG_USED/PageCgroupUsed sites can test that instead. > > Because this is the last page_cgroup flag, this patch reduces the > memcg per-page overhead to a single pointer. Nice. I have an old patch which stuck this flag into page_cgroup pointer but this is of course much much better! > Signed-off-by: Johannes Weiner Acked-by: Michal Hocko Just a nit below [...] > @@ -2525,9 +2523,10 @@ struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page) memcg = NULL initialization is not needed now > VM_BUG_ON_PAGE(!PageLocked(page), page); > > pc = lookup_page_cgroup(page); > - if (PageCgroupUsed(pc)) { > - memcg = pc->mem_cgroup; > - if (memcg && !css_tryget_online(&memcg->css)) > + memcg = pc->mem_cgroup; > + > + if (memcg) { > + if (!css_tryget_online(&memcg->css)) > memcg = NULL; > } else if (PageSwapCache(page)) { > ent.val = page_private(page); > #else > static inline void memcg_unregister_all_caches(struct mem_cgroup *memcg) [...] -- Michal Hocko SUSE Labs -- 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