Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756714Ab2FOKum (ORCPT ); Fri, 15 Jun 2012 06:50:42 -0400 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:48339 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756546Ab2FOKuk (ORCPT ); Fri, 15 Jun 2012 06:50:40 -0400 From: "Aneesh Kumar K.V" To: Michal Hocko Cc: linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com, dhillf@gmail.com, rientjes@google.com, akpm@linux-foundation.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: Re: [PATCH -V9 14/15] hugetlb/cgroup: migrate hugetlb cgroup info from oldpage to new page during migration In-Reply-To: <20120614100454.GL27397@tiehlicka.suse.cz> References: <1339583254-895-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1339583254-895-15-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20120614100454.GL27397@tiehlicka.suse.cz> User-Agent: Notmuch/0.13.2+35~g0ff57e7 (http://notmuchmail.org) Emacs/24.1.50.1 (x86_64-unknown-linux-gnu) Date: Fri, 15 Jun 2012 16:20:31 +0530 Message-ID: <87haucn91k.fsf@skywalker.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain x-cbid: 12061500-1396-0000-0000-000001656A8E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1742 Lines: 51 Michal Hocko writes: > On Wed 13-06-12 15:57:33, Aneesh Kumar K.V wrote: >> From: "Aneesh Kumar K.V" >> >> With HugeTLB pages, hugetlb cgroup is uncharged in compound page destructor. Since >> we are holding a hugepage reference, we can be sure that old page won't >> get uncharged till the last put_page(). >> >> Signed-off-by: Aneesh Kumar K.V > > Reviewed-by: Michal Hocko > > One question below > [...] >> +void hugetlb_cgroup_migrate(struct page *oldhpage, struct page *newhpage) >> +{ >> + struct hugetlb_cgroup *h_cg; >> + >> + if (hugetlb_cgroup_disabled()) >> + return; >> + >> + VM_BUG_ON(!PageHuge(oldhpage)); >> + spin_lock(&hugetlb_lock); >> + h_cg = hugetlb_cgroup_from_page(oldhpage); >> + set_hugetlb_cgroup(oldhpage, NULL); >> + cgroup_exclude_rmdir(&h_cg->css); >> + >> + /* move the h_cg details to new cgroup */ >> + set_hugetlb_cgroup(newhpage, h_cg); >> + spin_unlock(&hugetlb_lock); >> + cgroup_release_and_wakeup_rmdir(&h_cg->css); >> + return; >> +} >> + > > The changelog says that the old page won't get uncharged - which means > that the the cgroup cannot go away (even if we raced with the move > parent, hugetlb_lock makes sure we either see old or new cgroup) so why > do we need to play with css ref. counting? Ok hugetlb_lock should be sufficient here i guess. I will send a patch on top to remove the exclude_rmdir and release_and_wakeup_rmdir -aneesh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/