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Petersen" , Kanchan Joshi , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v7 0/3] FDP and per-io hints Message-ID: <20241010070736.de32zgad4qmfohhe@ArmHalley.local> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: CAMSVWEXC01.scsc.local (2002:6a01:e347::6a01:e347) To CAMSVWEXC02.scsc.local (2002:6a01:e348::6a01:e348) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrGKsWRmVeSWpSXmKPExsWy7djPc7pWtezpBk9P6FvMWbWN0WL13X42 i65/W1gsXh/+xGgx7cNPZot3Tb9ZLPYsmsRksXL1USaLd63nWCxmT29msniyfhazxaRD1xgt pkxrYrTYe0vbYs/ekywW85c9ZbdYfvwfk8W61+9ZLM7/Pc7qIOxx+Yq3x85Zd9k9zt/byOJx +Wypx6ZVnWwemz5NYvfYvKTeY/fNBjaPj09vsXi833eVzePMgiNA8dPVHp83yXlsevKWKYAv issmJTUnsyy1SN8ugStj2+VnLAXdIhXr515mamBsE+hi5OSQEDCR+HBsG3sXIxeHkMAKRok5 ky6xQThfGCWWfzgO5XxmlLh34QtTFyMHWMu7tSIQ8eWMErPmzmaHK9q06ggjhLOFUWL+s5Ps IEtYBFQlzm2ewQpiswnYS1xadosZxBYRUJa4O38mK0gDs8BBFokDP5aygCSEBQwk3n/vZQOx eQVsJdbM6GOEsAUlTs58AlbDLGAl0fmhiRXkJGYBaYnl/zhAwpwCWhLL2n8xQjynJPH4xVso u1bi1JZbTCC7JAR+cUocmzWFFSLhInFi5iEWCFtY4tXxLewQtozE6ck9UPFqiYaTJ6CaWxgl Wju2skLCwlqi70wORI2jROO8uWwQYT6JG28FIc7kk5i0bTozRJhXoqNNCKJaTWL1vTcsExiV ZyF5bBaSx2YhPLaAkXkVo3hqaXFuemqxcV5quV5xYm5xaV66XnJ+7iZGYNI8/e/41x2MK159 1DvEyMTBeIhRgoNZSYRXdyFruhBvSmJlVWpRfnxRaU5q8SFGaQ4WJXFe1RT5VCGB9MSS1OzU 1ILUIpgsEwenVAOTiaVV1sHXb+s+5+lpbjV7FffTPsj7U5H6V4UV3uWxt5uEPPvn8+3yEj65 c6+dUtOLTRbJ4e+5eyfz/pzg+Es3i110h07rJQ35Kj6dRUd+W3o5T4lx61jgqC3Z8ycjpdXf sO/3qc+rJpsWawad55mp77mz0M/y1Jnw+MM+D6Y+qXrl59lgWel/TWTRCeViLSbzzx/Cblzj 4EhiaCrvVvTIYxX69kS3lf1b6L2ofJW9m7vat5Qln5csmtL5/pXzM4MZz1gE3XbMf3RbZVNI dVmY/O8TbX/73vmYh1XcXyCct+uh8Grp7xW1/05aNOYKnHqx8JbojAVdLeKbMw6+PVd4+pjb yusdFyep3Nt0zkaJpTgj0VCLuag4EQB+kvMICQQAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprCKsWRmVeSWpSXmKPExsVy+t/xe7pWtezpBvvviFnMWbWN0WL13X42 i65/W1gsXh/+xGgx7cNPZot3Tb9ZLPYsmsRksXL1USaLd63nWCxmT29msniyfhazxaRD1xgt pkxrYrTYe0vbYs/ekywW85c9ZbdYfvwfk8W61+9ZLM7/Pc7qIOxx+Yq3x85Zd9k9zt/byOJx +Wypx6ZVnWwemz5NYvfYvKTeY/fNBjaPj09vsXi833eVzePMgiNA8dPVHp83yXlsevKWKYAv Ss+mKL+0JFUhI7+4xFYp2tDCSM/Q0kLPyMRSz9DYPNbKyFRJ384mJTUnsyy1SN8uQS9j2+Vn LAXdIhXr515mamBsE+hi5OCQEDCReLdWpIuRi0NIYCmjxOun21i7GDmB4jISG79chbKFJf5c 62KDKPrIKLH/5nxmCGcLo8SGYxcZQapYBFQlzm2eAdbBJmAvcWnZLWYQW0RAWeLu/JmsIA3M AgdZJKZtP8sGkhAWMJB4/70XzOYVsJVYM6OPEWJqP7PE7HXLWCESghInZz5hAbGZBSwkZs4/ zwhyN7OAtMTyfxwgYU4BLYll7b8YIU5Vknj84i2UXSvx+e8zxgmMwrOQTJqFZNIshEkLGJlX MYqklhbnpucWG+oVJ+YWl+al6yXn525iBCaPbcd+bt7BOO/VR71DjEwcjIcYJTiYlUR4dRey pgvxpiRWVqUW5ccXleakFh9iNAWGxURmKdHkfGD6yiuJNzQzMDU0MbM0MLU0M1YS53W7fD5N SCA9sSQ1OzW1ILUIpo+Jg1OqgWk+c2uQ+evkWxOE3SYdcd77cdH273urez9NmV0auO64m2HV 7FM39e4sZ00+2rzj4Em2Dbs6o2S4+lcUxtrcvHIm8P+OGOMTT/N2zVc63LEzRXAP52LvOU95 xGebSW3qcZ928MjnxtXNuz9+kS0/9Kq5bKVRy/lHu5NsGCc9b4vpXlYxQW3LtUaGREEBg4NL DpyV49BJD21/pPf1cEnQ1ffsM3++DKsqDlW9sUiys89527F05+92Bgut7B8nve82dbhy53Xk BQ21lhxBoIm7DZM23t5y18CvId2D6QbX9JZ+I4NlESc+e/efeX4yJj1K6n3tffXGRvfV396J 2hnNWJumWFjCpXy8W3+PfVv6RiWW4oxEQy3mouJEAHG/Lt2nAwAA X-CMS-MailID: 20241010070738eucas1p2057209e5f669f37ca586ad4a619289ed X-Msg-Generator: CA X-RootMTR: 20241010070738eucas1p2057209e5f669f37ca586ad4a619289ed X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20241010070738eucas1p2057209e5f669f37ca586ad4a619289ed References: <20241004053121.GB14265@lst.de> <20241004061811.hxhzj4n2juqaws7d@ArmHalley.local> <20241004062733.GB14876@lst.de> <20241004065233.oc5gqcq3lyaxzjhz@ArmHalley.local> <20241004123027.GA19168@lst.de> <20241007101011.boufh3tipewgvuao@ArmHalley.local> <20241008122535.GA29639@lst.de> <20241009092828.GA18118@lst.de> On 09.10.2024 09:06, Keith Busch wrote: >On Wed, Oct 09, 2024 at 11:28:28AM +0200, Christoph Hellwig wrote: >> On Tue, Oct 08, 2024 at 08:44:28AM -0600, Keith Busch wrote: >> > Then let's just continue with patches 1 and 2. They introduce no new >> > user or kernel APIs, and people have already reported improvements using >> > it. >> >> They are still not any way actually exposing the FDP functionality >> in the standard though. How is your application going to align >> anything to the reclaim unit? Or is this another of the cases where >> as a hyperscaler you just "know" from the data sheet? > >As far as I know, this is an inconsequential spec detail that is not >being considered by any applications testing this. And yet, the expected >imrpovements are still there, so I don't see a point holding this up for >that reason. I am re-reading the thread to find a common ground. I realize that my last email came sharper than I intended. I apologize for that Christoph. Let me summarize and propose something constructive so that we can move forward. It is clear that you have a lot of insight on how a FS API should look like to unify the different data placement alternatives across protocols. I have not seen code for it, but based on the technical feedback you are providing, it seems to be fairly clear in your mind. I think we should attempt to pursue that with an example in mind. Seems XFS is the clear candidate. You have done work already in enable SMR HDDs; it seems we can get FDP under that umbrella. This will however take time to get right. We can help with development, testing, and experimental evaluation on the WAF benefits for such an interface. However, this work should not block existing hardware enabling an existing use-case. The current patches are not intrusive. They do not make changse to the API and merely wire up what is there to the driver. Anyone using temperaturs will be able to use FDP - this is a win without a maintainance burden attached to it. The change to the FS / application API will not require major changes either; I believe we all agree that we cannot remove the temperatures, so all existing temperature users will be able to continue using them; we will just add an alternative for power users on the side. So the proposal is to merge the patches as they are and commit to work together on a new, better API for in-kernel users (FS), and for applications (syscall, uring). Christoph, would this be a viable way to move forward for you? Thanks, Javier