From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx150.postini.com [74.125.245.150]) by kanga.kvack.org (Postfix) with SMTP id 6BF226B006C for ; Mon, 9 Jul 2012 16:38:13 -0400 (EDT) Received: by yhr47 with SMTP id 47so14085591yhr.14 for ; Mon, 09 Jul 2012 13:38:12 -0700 (PDT) Date: Mon, 9 Jul 2012 13:37:39 -0700 (PDT) From: Hugh Dickins Subject: Re: [patch 03/11] mm: shmem: do not try to uncharge known swapcache pages In-Reply-To: <20120709144657.GF4627@tiehlicka.suse.cz> Message-ID: References: <1341449103-1986-1-git-send-email-hannes@cmpxchg.org> <1341449103-1986-4-git-send-email-hannes@cmpxchg.org> <20120709144657.GF4627@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Johannes Weiner , Andrew Morton , KAMEZAWA Hiroyuki , David Rientjes , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org On Mon, 9 Jul 2012, Michal Hocko wrote: > > Maybe I am missing something but who does the uncharge from: > shmem_unuse > mem_cgroup_cache_charge > shmem_unuse_inode > shmem_add_to_page_cache There isn't any special uncharge for shmem_unuse(): once the swapcache page is matched up with its memcg, it will get uncharged by one of the usual routes to swapcache_free() when the page is freed: maybe in the call from __remove_mapping(), maybe when free_page_and_swap_cache() ends up calling it. Perhaps you're worrying about error (or unfound) paths in shmem_unuse()? By the time we make the charge, we know for sure that it's a shmem page, and make the charge appropriately; in racy cases it might get uncharged again in the delete_from_swap_cache(). Can the unfound case occur these days? I'd have to think more deeply to answer that, but the charge will not go missing. Hugh -- 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