Hi Christoph, > Including the one this model causes on at least some SSDs where you now statically allocate resources to a stream that is now not globally available. Sorry but can you please elaborate the issue? I do not get what is being statically allocated which was globally available earlier. If you are referring to nvme driver, available streams at subsystem level are being reflected for all namespaces. This is same as earlier. There is no attempt to explicitly allocate (using dir-receive) or reserve streams for any namespace. Streams will continue to get allocated/released implicitly as and when writes (with stream id) arrive. > All for the little log with very short date lifetime that any half decent hot/cold partitioning algorithm in the SSD should be able to detect. With streams, hot/cold segregation is happening at the time of placement itself, without algorithm; that is a clear win over algorithms which take time/computation to be able to do the same. And infrastructure update (write-hint-to-stream-id conversion in block-layer, in-kernel hints etc.) seems to be required anyway for streams to extend its reach beyond nvme and user-space hints. Thanks, -----Original Message----- From: Christoph Hellwig [mailto:hch@xxxxxxxxxxxxx] Sent: Friday, May 10, 2019 10:33 PM To: Kanchan Joshi <joshi.k@xxxxxxxxxxx> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-block@xxxxxxxxxxxxxxx; linux-nvme@xxxxxxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx; linux-ext4@xxxxxxxxxxxxxxx; prakash.v@xxxxxxxxxxx; anshul@xxxxxxxxxxx Subject: Re: [PATCH v5 0/7] Extend write-hint framework, and add write-hint for Ext4 journal I think this fundamentally goes in the wrong direction. We explicitly designed the block layer infrastructure around life time hints and not the not fish not flesh streams interface, which causes all kinds of problems. Including the one this model causes on at least some SSDs where you now statically allocate resources to a stream that is now not globally available. All for the little log with very short date lifetime that any half decent hot/cold partitioning algorithm in the SSD should be able to detect.
