From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH v3 1/5] mm: introduce MADV_COLD Date: Thu, 27 Jun 2019 16:53:02 +0200 Message-ID: <20190627145302.GC5303@dhcp22.suse.cz> References: <20190627115405.255259-1-minchan@kernel.org> <20190627115405.255259-2-minchan@kernel.org> <343599f9-3d99-b74f-1732-368e584fa5ef@intel.com> <20190627140203.GB5303@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Dave Hansen Cc: Minchan Kim , Andrew Morton , linux-mm , LKML , linux-api@vger.kernel.org, Johannes Weiner , Tim Murray , Joel Fernandes , Suren Baghdasaryan , Daniel Colascione , Shakeel Butt , Sonny Rao , oleksandr@redhat.com, hdanton@sina.com, lizeb@google.com, "Kirill A . Shutemov" List-Id: linux-api@vger.kernel.org On Thu 27-06-19 07:36:50, Dave Hansen wrote: [...] > For MADV_COLD, if we defined it like this, I think we could use it for > both purposes (demotion and LRU movement): > > Pages in the specified regions will be treated as less-recently- > accessed compared to pages in the system with similar access > frequencies. In contrast to MADV_DONTNEED, the contents of the you meant s@MADV_DONTNEED@MADV_FREE@ I suppose > region are preserved. > > It would be nice not to talk about reclaim at all since we're not > promising reclaim per se. Well, I guess this is just an implementation detail. MADV_FREE is really only about aging. It is up to the kernel what to do during the reclaim and the advice doesn't and shouldn't make any difference here. Now MADV_PAGEOUT would be more tricky in that direction because it defines an immediate action to page out the range. I do understand your argument about NUMA unaware applications which might want to get something like MADV_DEMOTE which would move a page to a secondary memory (whatever that is) but I think this is asking for its own madvise. MADV_PAGEOUT has a quite simple semnatic - move to the backing storage - and I would rather not make it more complex. -- Michal Hocko SUSE Labs