On Mon, Oct 02, 2023 at 01:37:59PM +0200, Niklas Cassel wrote: > On Wed, Sep 27, 2023 at 03:14:10PM -0400, Martin K. Petersen wrote: > > > > Hi Bart! > > > > > Zoned UFS vendors need the data temperature information. Hence this > > > patch series that restores write hint information in F2FS and in the > > > block layer. The SCSI disk (sd) driver is modified such that it passes > > > write hint information to SCSI devices via the GROUP NUMBER field. > > > > I don't have any particular problems with your implementation, although > > I'm still trying to wrap my head around how to make this coexist with my > > I/O hinting series. But I guess there's probably not going to be a big > > overlap between devices that support both features. > > Hello Bart, Martin, > > I don't know which user facing API Martin's I/O hinting series is intending > to use. > > However, while discussing this series at ALPSS, we did ask ourselves why this > series is not reusing the already existing block layer API for providing I/O > hints: > https://github.com/torvalds/linux/blob/v6.6-rc4/include/uapi/linux/ioprio.h#L83-L103 > > We can have 1023 possible I/O hints, and so far we are only using 7, which > means that there are 1016 possible hints left. > This also enables you to define more than the 4 previous temperature hints > (extreme, long, medium, short), if so desired. > > There is also support in fio for these I/O hints: > https://github.com/axboe/fio/blob/master/HOWTO.rst?plain=1#L2294-L2302 > > When this new I/O hint API has added, there was no other I/O hint API > in the kernel (since the old fcntl() F_GET_FILE_RW_HINT / F_SET_FILE_RW_HINT > API had already been removed when this new API was added). > > So there should probably be a good argument why we would want to introduce > yet another API for providing I/O hints, instead of extending the I/O hint > API that we already have in the kernel right now. > (Especially since it seems fairly easy to modify your patches to reuse the > existing API.) One argument might be that the current I/O hints API does not allow hints to be stacked. So one would not e.g. be able to combine a command duration limit with a temperature hint... Kind regards, Niklas
