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Sun, 06 Dec 2020 23:13:01 -0800 (PST) Received: from js1304-desktop ([114.206.198.176]) by smtp.gmail.com with ESMTPSA id g16sm11002537pfh.187.2020.12.06.23.12.55 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sun, 06 Dec 2020 23:13:00 -0800 (PST) Date: Mon, 7 Dec 2020 16:12:50 +0900 From: Joonsoo Kim To: Pavel Tatashin Cc: Jason Gunthorpe , LKML , linux-mm , Andrew Morton , Vlastimil Babka , Michal Hocko , David Hildenbrand , Oscar Salvador , Dan Williams , Sasha Levin , Tyler Hicks , mike.kravetz@oracle.com, Steven Rostedt , Ingo Molnar , Peter Zijlstra , Mel Gorman , Matthew Wilcox , David Rientjes , John Hubbard Subject: Re: [PATCH 0/6] prohibit pinning pages in ZONE_MOVABLE Message-ID: <20201207071238.GA10731@js1304-desktop> References: <20201202052330.474592-1-pasha.tatashin@soleen.com> <20201204035953.GA17056@js1304-desktop> <20201204161005.GD5487@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Dec 04, 2020 at 12:50:56PM -0500, Pavel Tatashin wrote: > > > Yes, this indeed could be a problem for some configurations. I will > > > add your comment to the commit log of one of the patches. > > > > It sounds like there is some inherent tension here, breaking THP's > > when doing pin_user_pages() is a really nasty thing to do. DMA > > benefits greatly from THP. > > > > I know nothing about ZONE_MOVABLE, is this auto-setup or an admin > > option? If the result of this patch is standard systems can no longer > > pin > 80% of their memory I have some regression concerns.. > > ZONE_MOVABLE can be configured via kernel parameter, or when memory > nodes are onlined after hot-add; so this is something that admins > configure. ZONE_MOVABLE is designed to gurantee memory hot-plug Just note, the origin of ZONE_MOVABLE is to provide availability of huge page, especially, hugetlb page. AFAIK, not guarantee memory hot-plug. See following commit that introduces the ZONE_MOVABLE. 2a1e274 Create the ZONE_MOVABLE zone > functionality, and not availability of THP, however, I did not know > about the use case where some admins might configure ZONE_MOVABLE to The usecase is lightly mentioned in previous discussion. http://lkml.kernel.org/r/alpine.DEB.2.23.453.2011221300100.2830030@chino.kir.corp.google.com Anyway, I agree with your other arguments and this patchset. Thanks.