On 2018/10/12 16:33, Hannes Reinecke wrote: > On 10/12/18 4:30 AM, Damien Le Moal wrote: >> Handling checks of ZBC device capacity using the max_lba field of the >> REPORT ZONES command reply for disks with rc_basis == 0 can be done >> using the same report zones command reply used to check the "same" >> field. >> >> Avoid executing a report zones command solely to check the disk capacity >> by merging sd_zbc_check_capacity() into sd_zbc_check_zone_size() and >> renaming that function to sd_zbc_check_zones(). This removes a costly >> execution of a full report zones command and so reduces device scan >> duration at boot time as well as the duration of disk revalidate calls. >> >> Furthermore, setting the partial report bit in the REPORT ZONES command >> cdb can significantly reduce this command execution time as the device >> does not have to count and report the total number of zones that could >> be reported assuming a large enough reply buffer. A non-partial zone >> report is necessary only for the first execution of report zones used to >> check the same field value (to ensure that this value applies to all >> zones of the disk). All other calls to sd_zbc_report_zones() can use a >> partial report to reduce execution time. >> >> Using a 14 TB ZBC disk, these simple changes reduce device scan time at >> boot from about 3.5s down to about 900ms. Disk revalidate times are also >> reduced from about 450ms down to 230ms. >> >> Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx> >> Reviewed-by: Christoph Hellwig <hch@xxxxxx> >> --- >> drivers/scsi/sd_zbc.c | 94 ++++++++++++++++++------------------------- >> 1 file changed, 40 insertions(+), 54 deletions(-) >> > Reviewed-by: Hannes Reinecke <hare@xxxxxxxx> > > ... and it'll be your fault if there are drives which do not support the > 'partial' bit :) The partial bit definition is in the ZBC/ZAC specs and it is not optional. If a drive does not support it, it would be out of specs :) > > Cheers, > > Hannes > -- Damien Le Moal Western Digital Research
