From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH 19/19] mm: memcontrol: update page->mem_cgroup stability rules Date: Thu, 11 Jun 2020 11:40:33 +0200 Message-ID: <20200611094033.GC20450@dhcp22.suse.cz> References: <20200508183105.225460-1-hannes@cmpxchg.org> <20200508183105.225460-20-hannes@cmpxchg.org> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20200508183105.225460-20-hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Johannes Weiner Cc: Andrew Morton , Alex Shi , Joonsoo Kim , Shakeel Butt , Hugh Dickins , "Kirill A. Shutemov" , Roman Gushchin , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org On Fri 08-05-20 14:31:06, Johannes Weiner wrote: > The previous patches have simplified the access rules around > page->mem_cgroup somewhat: > > 1. We never change page->mem_cgroup while the page is isolated by > somebody else. This was by far the biggest exception to our rules > and it didn't stop at lock_page() or lock_page_memcg(). > > 2. We charge pages before they get put into page tables now, so the > somewhat fishy rule about "can be in page table as long as it's > still locked" is now gone and boiled down to having an exclusive > reference to the page. > > Document the new rules. Any of the following will stabilize the > page->mem_cgroup association: > > - the page lock > - LRU isolation > - lock_page_memcg() > - exclusive access to the page > > Signed-off-by: Johannes Weiner > Reviewed-by: Alex Shi > Reviewed-by: Joonsoo Kim Thanks a lot this is a big improvement and simplification. I have gone through the whole series finally. I have followed up where necessary but overall this is really nice! Sorry I couldn't jump in to review in time. -- Michal Hocko SUSE Labs