On 2018-01-19 21:58, John Snow wrote: > We're attempting to slacken the mirror loop in three different places, > but we can combine these three attempts. Combine the early loop call to > block_job_pause_point with the two late-loop calls to block_job_sleep_ns. > > When delay_ns is 0 and it has not been SLICE_TIME since the last yield, > block_job_relax is merely a call to block_job_pause_point, so this should > be equivalent with the exception that if we have managed to not yield at > all in the last SLICE_TIME ns, we will now do so. > > I am not sure that condition was possible, > so this loop should be equivalent.
Well, to me it even sounds like a positive change if it was a change.
We want the job to yield after SLICE_TIME ns, after all, and I don't
think it matters where that happens, exactly.
>
> Signed-off-by: John Snow <js...@redhat.com>
> ---
> block/mirror.c | 22 +++++++++++-----------
> block/trace-events | 2 +-
> 2 files changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/block/mirror.c b/block/mirror.c
> index a0e0044de2..192e03694f 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -761,7 +761,7 @@ static void coroutine_fn mirror_run(void *opaque)
> assert(!s->dbi);
> s->dbi = bdrv_dirty_iter_new(s->dirty_bitmap);
> for (;;) {
> - uint64_t delay_ns = 0;
> + static uint64_t delay_ns = 0;
Errr. Are you sure about that?
Now every mirror job in the qeny process will share this single
variable. Was that your intention?
> int64_t cnt, delta;
> bool should_complete;
>
> @@ -770,9 +770,16 @@ static void coroutine_fn mirror_run(void *opaque)
> goto immediate_exit;
> }
>
> - block_job_pause_point(&s->common);
> -
> cnt = bdrv_get_dirty_count(s->dirty_bitmap);
> +
> + trace_mirror_before_relax(s, cnt, s->synced, delay_ns);
> + if (block_job_relax(&s->common, delay_ns)) {
See the reply to <a href="HEAD^^">that patch</a>.
> + if (!s->synced) {
> + goto immediate_exit;
> + }
> + }
> + delay_ns = 0;
> +
> /* s->common.offset contains the number of bytes already processed so
> * far, cnt is the number of dirty bytes remaining and
> * s->bytes_in_flight is the number of bytes currently being
> @@ -849,15 +856,8 @@ static void coroutine_fn mirror_run(void *opaque)
> }
>
> ret = 0;
> - trace_mirror_before_sleep(s, cnt, s->synced, delay_ns);
> - if (!s->synced) {
> - block_job_sleep_ns(&s->common, delay_ns);
> - if (block_job_is_cancelled(&s->common)) {
> - break;
> - }
> - } else if (!should_complete) {
> + if (s->synced && !should_complete) {
> delay_ns = (s->in_flight == 0 && cnt == 0 ? SLICE_TIME : 0);
> - block_job_sleep_ns(&s->common, delay_ns);
> }
> }
Basic idea looks good to me (apart from the static delay_ns), but, well,
block-job-cancel on a busy job still breaks.
Max
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