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[142.162.115.133]) by smtp.gmail.com with ESMTPSA id j46sm1828038qtk.1.2021.02.10.10.04.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Feb 2021 10:04:06 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1l9tqP-0068Ck-JW; Wed, 10 Feb 2021 14:04:05 -0400 Date: Wed, 10 Feb 2021 14:04:05 -0400 From: Jason Gunthorpe To: "Song Bao Hua (Barry Song)" Cc: David Hildenbrand , "Wangzhou (B)" , "linux-kernel@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "linux-mm@kvack.org" , "linux-arm-kernel@lists.infradead.org" , "linux-api@vger.kernel.org" , Andrew Morton , Alexander Viro , "gregkh@linuxfoundation.org" , "kevin.tian@intel.com" , "jean-philippe@linaro.org" , "eric.auger@redhat.com" , "Liguozhu (Kenneth)" , "zhangfei.gao@linaro.org" , "chensihang (A)" Subject: Re: [RFC PATCH v3 1/2] mempinfd: Add new syscall to provide memory pin Message-ID: <20210210180405.GP4718@ziepe.ca> References: <1612685884-19514-1-git-send-email-wangzhou1@hisilicon.com> <1612685884-19514-2-git-send-email-wangzhou1@hisilicon.com> <20210208183348.GV4718@ziepe.ca> <0dca000a6cd34d8183062466ba7d6eaf@hisilicon.com> <20210208213023.GZ4718@ziepe.ca> <0868d209d7424942a46d1238674cf75d@hisilicon.com> <20210209135331.GF4718@ziepe.ca> <2527b4ac8df14fa1b427bef65dace719@hisilicon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2527b4ac8df14fa1b427bef65dace719@hisilicon.com> 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 Tue, Feb 09, 2021 at 10:22:47PM +0000, Song Bao Hua (Barry Song) wrote: > The problem is that SVA declares we can use any memory of a process > to do I/O. And in real scenarios, we are unable to customize most > applications to make them use the pool. So we are looking for some > extension generically for applications such as Nginx, Ceph. But those applications will suffer jitter even if their are using CPU to do the same work. I fail to see why adding an accelerator suddenly means the application owner will care about jitter introduced by migration/etc. Again in proper SVA it should be quite unlikely to take a fault caused by something like migration, on the same likelyhood as the CPU. If things are faulting so much this is a problem then I think it is a system level problem with doing too much page motion. Jason