From mboxrd@z Thu Jan 1 00:00:00 1970 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=fb.com; h=from : to : cc : subject : date : message-id : references : in-reply-to : content-type : content-transfer-encoding : mime-version; s=facebook; bh=Onl8n58+kA3lF51Bl6Lp+FisZnDJcHsQHHzFaQWUvt0=; b=eSYilh++b7B9S7z9cmMDhsElaAN3nIRZXyhOX0tgjDWOGrF2udwmajVrsBS5W8js9QNr s0bh0DbLixAb1tUZStsZFjueamroYVD0cl/lvLW7XdGR7ktqtomEhEbJx+vdixXTiYWM hRp5jnHDjup40tBiNHREN0IyKXbv/z8vVoU= In-Reply-To: <20160207184059.GB19151@esperanza> Content-Language: en-US Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: To: Vladimir Davydov Cc: Johannes Weiner , Andrew Morton , Hugh Dickins , Michal Hocko , Mateusz Guzik , Sergey Senozhatsky , "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org" , "cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Kernel Team > On Feb 7, 2016, at 1:41 PM, Vladimir Davydov wrote: > >> 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. >> >> 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. >> >> 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. >> >> Signed-off-by: Johannes Weiner >> Suggested-by: Hugh Dickins > > Acked-by: Vladimir Davydov Thanks! > @@ -5483,6 +5483,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) > unsigned int nr_pages; > bool compound; > > + 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 from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html