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[216.228.112.22]) by smtp.gmail.com with ESMTPSA id v18sm28129738pfm.165.2019.03.27.11.42.36 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 27 Mar 2019 11:42:36 -0700 (PDT) Date: Wed, 27 Mar 2019 11:42:32 -0700 From: Nicolin Chen To: Christoph Hellwig Subject: Re: [PATCH v2 RFC/RFT 0/5] Save single pages from CMA area Message-ID: <20190327184231.GA13287@Asurada-Nvidia> References: <20190326230131.16275-1-nicoleotsuka@gmail.com> <20190327080821.GB20336@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190327080821.GB20336@lst.de> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190327_114238_849957_EC9EB5D2 X-CRM114-Status: GOOD ( 13.97 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: tony@atomide.com, catalin.marinas@arm.com, joro@8bytes.org, will.deacon@arm.com, linux@armlinux.org.uk, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org, m.szyprowski@samsung.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Mar 27, 2019 at 09:08:21AM +0100, Christoph Hellwig wrote: > On Tue, Mar 26, 2019 at 04:01:26PM -0700, Nicolin Chen wrote: > > This series of patches try to save single pages from CMA area bypassing > > all CMA single page alloctions and allocating normal pages instead, as > > all addresses within one single page are contiguous. > > > > We had once applied the PATCH-5 but reverted it as actually not all the > > callers handled the fallback allocations. Per Robin's suggestion, let's > > stuff alloc_pages()/free_page() fallbacks to those callers before having > > PATCH-5. > > Given the problems this has caused so far I'd like to see a good > explanation of why this optimization is so important that all the churn > is even worth it.. With certain downstream user cases, we had run into a CMA exhaustion situation, and this was one of the changes that eased the problem. I have all the reasoning in the PATCH-5 commit message. And what Robin tested can also justify for it: https://lore.kernel.org/patchwork/patch/1004934/#1190139 Thanks _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel