On 4/2/20 1:21 PM, Alexey Dobriyan wrote: > If thread bumps into "max_open_zones" limit, it tries to close/reopen some > other zone before issuing IO. This scan is done over full list of block device's > opened zones. It means that a zone which doesn't belong to thread's working > area can be altered or IO can be retargeted at such zone. > > If IO is retargeted then it will be dropped by "is_valid_offset()" check. > > What happens with null block device testing is that one thread monopolises > IO and others threads do basically nothing. > > This config will reliably succeed now: > > [global] > zonemode=zbd > zonesize=1M > rw=randwrite > ... > thread > numjobs=2 > offset_increment=128M > > [j] > max_open_zones=2 > size=2M > > Starting 2 threads > zbd 7991 /dev/nullb0: zbd model string: host-managed > zbd 7991 Device /dev/nullb0 has 1024 zones of size 1024 KB > zbd 8009 /dev/nullb0: examining zones 0 .. 2 > zbd 8010 /dev/nullb0: examining zones 128 .. 130 > zbd 8009 /dev/nullb0: opening zone 0 > zbd 8010 /dev/nullb0: opening zone 128 > zbd 8009 /dev/nullb0: queued I/O (0, 4096) for zone 0 > zbd 8009 zbd_convert_to_open_zone(/dev/nullb0): starting from zone 128 (offset 1552384, buflen 4096) > > retargeted for other thread's zone (zone 0 => zone 128) > > zbd 8010 /dev/nullb0: queued I/O (134217728, 4096) for zone 128 > zbd 8009 zbd_convert_to_open_zone(/dev/nullb0): returning zone 128 > zbd 8009 Dropped request with offset 134221824 > > and dropped > > Note: quasi-randomness is kind of necessary to spread I/O. Imagine index 0 > is picked all the time, zone living there will be reopened constantly and > get relatively little I/O. Applied, thanks. -- Jens Axboe
