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[5.186.124.214]) by smtp.gmail.com with ESMTPSA id j20sm874968ejy.124.2020.12.09.01.17.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Dec 2020 01:17:06 -0800 (PST) Date: Wed, 9 Dec 2020 10:17:05 +0100 From: Javier =?utf-8?B?R29uesOhbGV6?= To: Johannes Thumshirn Cc: Hannes Reinecke , Christoph Hellwig , SelvaKumar S , "linux-nvme@lists.infradead.org" , "kbusch@kernel.org" , "axboe@kernel.dk" , Damien Le Moal , "sagi@grimberg.me" , "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "dm-devel@redhat.com" , "snitzer@redhat.com" , "selvajove@gmail.com" , "nj.shetty@samsung.com" , "joshi.k@samsung.com" , "Martin K. Petersen" , Bart Van Assche , Mikulas Patocka , "linux-scsi@vger.kernel.org" Subject: Re: [RFC PATCH v2 0/2] add simple copy support Message-ID: <20201209091705.brzbbqedavtxvhms@mpHalley> References: <20201204094659.12732-1-selvakuma.s1@samsung.com> <20201207141123.GC31159@lst.de> <01fe46ac-16a5-d4db-f23d-07a03d3935f3@suse.de> <20201207192453.vc6clbdhz73hzs7l@mpHalley> <20201208122248.utv7pqthmmn6uwv6@mpHalley> <20201208131333.xoxincxcnh7iz33z@mpHalley> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08.12.2020 13:24, Johannes Thumshirn wrote: >On 08/12/2020 14:13, Javier González wrote: >> On 08.12.2020 12:37, Johannes Thumshirn wrote: >>> On 08/12/2020 13:22, Javier González wrote: >>>> Good idea. Are you thinking of a sysfs entry to select the backend? >>> >>> Not sure on this one, initially I thought of a sysfs file, but then >>> how would you do it. One "global" sysfs entry is probably a bad idea. >>> Having one per block device to select native vs emulation maybe? And >>> a good way to benchmark. >> >> I was thinking a per block device to target the use case where a certain >> implementation / workload is better one way or the other. > >Yes something along those lines. > >>> >>> The other idea would be a benchmark loop on boot like the raid library >>> does. >>> >>> Then on the other hand, there might be workloads that run faster with >>> the emulation and some that run faster with the hardware acceleration. >>> >>> I think these points are the reason the last attempts got stuck. >> >> Yes. I believe that any benchmark we run would be biased in a certain >> way. If we can move forward with a sysfs entry and default to legacy >> path, we would not alter current behavior and enable NVMe copy offload >> (for now) for those that want to use it. We can then build on top of it. >> >> Does this sound like a reasonable approach? >> > >Yes this sounds like a reasonable approach to me. Cool. We will add this to the V3 then. Thanks Johannes!