From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id 9E6A5830B2 for ; Sun, 7 Feb 2016 14:23:56 -0500 (EST) Received: by mail-pa0-f53.google.com with SMTP id uo6so63233279pac.1 for ; Sun, 07 Feb 2016 11:23:56 -0800 (PST) Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com. [67.231.145.42]) by mx.google.com with ESMTPS id 10si9039266pfb.71.2016.02.07.11.23.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 07 Feb 2016 11:23:55 -0800 (PST) From: Johannes Weiner Subject: Re: [PATCH 2/2] mm: memcontrol: drop unnecessary lru locking from mem_cgroup_migrate() Date: Sun, 7 Feb 2016 18:57:49 +0000 Message-ID: <28CC6A8F-E642-4DF5-A8E5-DB9BB62DA429@fb.com> References: <1454616467-8994-1-git-send-email-hannes@cmpxchg.org> <1454616467-8994-2-git-send-email-hannes@cmpxchg.org>,<20160207184059.GB19151@esperanza> In-Reply-To: <20160207184059.GB19151@esperanza> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Vladimir Davydov Cc: Johannes Weiner , Andrew Morton , Hugh Dickins , Michal Hocko , Mateusz Guzik , Sergey Senozhatsky , "linux-mm@kvack.org" , "cgroups@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Kernel Team > On Feb 7, 2016, at 1:41 PM, Vladimir Davydov wro= te: >=20 >> On Thu, Feb 04, 2016 at 03:07:47PM -0500, Johannes Weiner wrote: >> Migration accounting in the memory controller used to have to handle >> both oldpage and newpage being on the LRU already; fuse's page cache >> replacement used to pass a recycled newpage that had been uncharged >> but not freed and removed from the LRU, and the memcg migration code >> used to uncharge oldpage to "pass on" the existing charge to newpage. >>=20 >> Nowadays, pages are no longer uncharged when truncated from the page >> cache, but rather only at free time, so if a LRU page is recycled in >> page cache replacement it'll also still be charged. And we bail out of >> the charge transfer altogether in that case. Tell commit_charge() that >> we know newpage is not on the LRU, to avoid taking the zone->lru_lock >> unnecessarily from the migration path. >>=20 >> But also, oldpage is no longer uncharged inside migration. We only use >> oldpage for its page->mem_cgroup and page size, so we don't care about >> its LRU state anymore either. Remove any mention from the kernel doc. >>=20 >> Signed-off-by: Johannes Weiner >> Suggested-by: Hugh Dickins >=20 > Acked-by: Vladimir Davydov Thanks! > @@ -5483,6 +5483,7 @@ void mem_cgroup_migrate(struct page *oldpage, struc= t page *newpage) > unsigned int nr_pages; > bool compound; >=20 > + VM_BUG_ON_PAGE(PageLRU(newpage), newpage); That's actually possible for fuse. But in that case newpage is charged and = we bail.= -- 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