On 2020/03/21 3:06, 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 devices'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 other thread 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
>
> Signed-off-by: Alexey Dobriyan (SK hynix) <adobriyan@xxxxxxxxx>
> ---
>
> zbd.c | 35 ++++++++++++++++++++++++++++++-----
> 1 file changed, 30 insertions(+), 5 deletions(-)
>
> --- a/zbd.c
> +++ b/zbd.c
> @@ -969,9 +969,8 @@ static struct fio_zone_info *zbd_convert_to_open_zone(struct thread_data *td,
> * This statement accesses f->zbd_info->open_zones[] on purpose
> * without locking.
> */
> - zone_idx = f->zbd_info->open_zones[(io_u->offset -
> - f->file_offset) *
> - f->zbd_info->num_open_zones / f->io_size];
> + uint32_t tmp = io_u->offset * f->zbd_info->num_open_zones / f->real_file_size;
> + zone_idx = f->zbd_info->open_zones[tmp];
> } else {
> zone_idx = zbd_zone_idx(f, io_u->offset);
> }
> @@ -985,6 +984,8 @@ static struct fio_zone_info *zbd_convert_to_open_zone(struct thread_data *td,
> * has been obtained. Hence the loop.
> */
> for (;;) {
> + uint32_t tmp;
> +
> z = &f->zbd_info->zone_info[zone_idx];
>
> zone_lock(td, z);
> @@ -998,9 +999,33 @@ static struct fio_zone_info *zbd_convert_to_open_zone(struct thread_data *td,
> __func__, f->file_name);
> return NULL;
> }
> - open_zone_idx = (io_u->offset - f->file_offset) *
> - f->zbd_info->num_open_zones / f->io_size;
> + open_zone_idx = io_u->offset * f->zbd_info->num_open_zones / f->real_file_size;
> assert(open_zone_idx < f->zbd_info->num_open_zones);
> +
> + for (tmp = open_zone_idx; tmp < f->zbd_info->num_open_zones; tmp++) {
> + uint32_t tmpz = f->zbd_info->open_zones[tmp];
> + struct fio_zone_info *z = &f->zbd_info->zone_info[tmpz];
> +
> + if (is_valid_offset(f, z->start)) {
> + open_zone_idx = tmp;
> + goto found_candidate_zone;
> + }
> + }
> + for (tmp = 0; tmp < open_zone_idx; tmp++) {
> + uint32_t tmpz = f->zbd_info->open_zones[tmp];
> + struct fio_zone_info *z = &f->zbd_info->zone_info[tmpz];
> +
> + if (is_valid_offset(f, z->start)) {
> + open_zone_idx = tmp;
> + goto found_candidate_zone;
> + }
> +
> + }
Adding a comment above the loop to explain what is being searched for would be
nice. Also, you can combine these 2 loops into one for simplicity, something like:
for (i = 0, tmp = open_zone_idx; i < f->zbd_info->num_open_zones; i++, tmp++) {
unsigned int tmpz;
struct fio_zone_info *z
if (tmp >= f->zbd_info->num_open_zones)
tmp = 0;
tmpz = f->zbd_info->open_zones[tmp];
z = &f->zbd_info->zone_info[tmpz];
if (is_valid_offset(f, z->start)) {
open_zone_idx = tmp;
goto found_candidate_zone;
}
}
> + dprint(FD_ZBD, "%s(%s): no candidate zone\n",
> + __func__, f->file_name);
> + return NULL;
> +
> +found_candidate_zone:
> new_zone_idx = f->zbd_info->open_zones[open_zone_idx];
> if (new_zone_idx == zone_idx)
> break;
>
--
Damien Le Moal
Western Digital Research
