From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Aneesh Kumar K.V" Subject: Re: [PATCH -V8 14/16] hugetlb/cgroup: add charge/uncharge calls for HugeTLB alloc/free Date: Sat, 09 Jun 2012 18:39:06 +0530 Message-ID: <87pq98ljil.fsf@skywalker.in.ibm.com> References: <1339232401-14392-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1339232401-14392-15-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20120609092301.GF1761@cmpxchg.org>User-Agent: Notmuch/0.11.1+346~g13d19c3 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) Mime-Version: 1.0 Return-path: In-Reply-To: <20120609092301.GF1761@cmpxchg.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Johannes Weiner Cc: linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com, dhillf@gmail.com, rientjes@google.com, mhocko@suse.cz, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Johannes Weiner writes: > On Sat, Jun 09, 2012 at 02:29:59PM +0530, Aneesh Kumar K.V wrote: >> From: "Aneesh Kumar K.V" >> >> This adds necessary charge/uncharge calls in the HugeTLB code. We do >> hugetlb cgroup charge in page alloc and uncharge in compound page destructor. >> >> Signed-off-by: Aneesh Kumar K.V >> --- >> mm/hugetlb.c | 16 +++++++++++++++- >> mm/hugetlb_cgroup.c | 7 +------ >> 2 files changed, 16 insertions(+), 7 deletions(-) >> >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index bf79131..4ca92a9 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -628,6 +628,8 @@ static void free_huge_page(struct page *page) >> BUG_ON(page_mapcount(page)); >> >> spin_lock(&hugetlb_lock); >> + hugetlb_cgroup_uncharge_page(hstate_index(h), >> + pages_per_huge_page(h), page); > > hugetlb_cgroup_uncharge_page() takes the hugetlb_lock, no? Yes, But this patch also modifies it to not take the lock, because we hold spin_lock just below in the call site. I didn't want to drop the lock and take it again. > > It's quite hard to review code that is split up like this. Please > always keep the introduction of new functions in the same patch that > adds the callsite(s). One of the reason I split the charge/uncharge routines and the callers in separate patches is to make it easier for review. Irrespective of the call site charge/uncharge routines should be correct with respect to locking and other details. What I did in this patch is a small optimization of avoiding dropping and taking the lock again. May be the right approach would have been to name it __hugetlb_cgroup_uncharge_page and make sure the hugetlb_cgroup_uncharge_page still takes spin_lock. But then we don't have any callers for that. -aneesh