On 03/06/2016 01:28 PM, Wouter Verhelst wrote: > Hi all, > > On Fri, Mar 04, 2016 at 03:03:26PM +0100, Paolo Bonzini wrote: >> NBD-wise, I think the TRIM command is good as it is, and >> NBD_CMD_WRITE_ZEROES should be added like Den is doing. >> >> It also makes sense to use trimming to implement NBD_CMD_WRITE_ZEROES, >> but it should be explicitly requested by the user. For this, my >> suggestion is that NBD_CMD_WRITE_ZEROES should have an >> NBD_FLAG_TRY_TRIM flag in bit 16. If specified, the backend can use a >> zero-writing mechanism that trims, _but_ it must ensure that the bytes >> read as zero. If it cannot ensure that, it must not trim and it >> should instead do a full write. This is similar to the SCSI command >> WRITE SAME (when the command payload is all zeroes). Like Kevin said, >> it also happens to map nicely to the QEMU block device layer. > That seems like a sensible approach, yes. > > Would one of you who feels strongly about this be willing to write up a > proposed spec for that? I could do it, but since I'm not 100% sure I > understand all the specific requirements, I'm uncomfortable doing so. > > If that doesn't raise any obvious issues that I'm aware of, I'd be happy > to add it to the "experimental" section of the proto.md file. > > (speaking of which, I notice that the STARTTLS patches got merged into > qemu, so I've moved the description of that to the main body and out of > the "experimental" part of that document) > I am going to send next RFC next Wednesday. Just waited other opinions not from QEMU side.
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