Re: [PATCH 00/13] Pass data temperature information to zoned UFS devices

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On Tue, Oct 03, 2023 at 10:26:27AM -0700, Bart Van Assche wrote:
> On 10/2/23 18:40, Martin K. Petersen wrote:
> > 
> > Niklas,
> > 
> > > I don't know which user facing API Martin's I/O hinting series is
> > > intending to use.
> > 
> > I'm just using ioprio.
> 
> Hi Martin,
> 
> Do you plan to use existing bits from the ioprio bitmask or new bits? Bits
> 0-2 are used for the priority level. Bits 3-5 are used for CDL. Bits 13-15
> are used for the I/O priority. The SCSI and NVMe standard define 64
> different data lifetimes (six bits). So there are 16 - 3 - 3 - 6 = 4
> remaining bits.

Hello Bart,

I think the math is:

16 - 3 (prio level) - 3 (CDL) - 3 (prio class) = 7

so if we want 64 different values for data lifetimes
(we previously only had 4 different values), that is 6 bits:

16 - 3 (prio level) - 3 (CDL) - 3 (prio class) - 6 (lifetime) = 1

so only one bit left for Martin :)

Not very much room to play with...


Kind regards,
Niklas




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