> > > Measurements have shown that for some UFS devices the maximum > > sequential > > I/O throughput is achieved with a transfer size above 512 KiB. Hence > > increase the maximum size of the data buffer associated with a single > > request from SCSI_DEFAULT_MAX_SECTORS (1024) * 512 bytes = 512 KiB > > into > > 1 GiB. > Did you choose 1GB to align with BLK_DEF_MAX_SECTORS? > If so why not just use it? > Can you share those performance measurements? > For some reason, I always thought that SR performance is saturated > somewhere around 1MB. 1GB seems excessive, so I tried to look it up in the UFS spec. There can be at most 255 RTTs per command upiu (bDeviceRTTCap is a single byte - in UFS4.0 as well), Each RTT correspond to a data-out/data-in UPIU which can hold up to 64KB. So at most 255x64KB, Or did I get it wrong? > > Note: the maximum data buffer size supported by the UFSHCI specification > > is 65535 * 256 MiB or about 16 TiB. Can you help me find this limit in UFSHCI? Thanks, Avri
