On Mon, 2019-07-15 at 12:28 +0300, Maxim Levitsky wrote: > > To be honest, the spec explicitly states that minimum submission queue entry > size is 64 > and minimum completion entry size should be is 16 bytes for NVM command set: > > "Bits 3:0 define the required (i.e., minimum) Submission Queue Entry size when > using the NVM Command Set. This is the minimum entry size that may be used. > The value is in bytes and is reported as a power of two (2^n). The required > value > shall be 6, corresponding to 64."
Yes, I saw that :-) Apple seems to ignore this and CC:IOSQES and effectively hard wire a size of 7 (128 bytes) for the IO queue. > "Bits 3:0 define the required (i.e., minimum) Completion Queue entry size > when using > the NVM Command Set. This is the minimum entry size that may be used. The > value > is in bytes and is reported as a power of two (2^n). The required value shall > be 4, > corresponding to 16." > > Pages 136/137, NVME 1.3d. > > In theory the spec allows for non NVM IO command set, and for which the sq/cq > entry sizes can be of any size, > as indicated in SQES/CQES and set in CC.IOCQES/CC.IOSQES, but than most of > the spec won't apply to it. > > > Also FYI, values in CC (IOCQES/IOSQES) are for I/O queues, which kind of > implies that admin queue, > should always use the 64/16 bytes entries, although I haven't found any > explicit mention of that. Right, and it does on the Apple HW as well. Cheers, Ben.
