On Sat 19 Aug 2017 05:23:12 PM CEST, Manos Pitsidianakis wrote:
- /* If the bucket is full then we have to wait */
- extra = bkt->level - bkt->max * bkt->burst_length;
+ if (!bkt->max) {
+ /* If bkt->max is 0 we still want to allow short bursts of I/O
+ * from the guest, otherwise every other request will be throttled
+ * and performance will suffer considerably. */
+ bucket_size = bkt->avg / 10;
+ burst_bucket_size = 0;
Might be wrong, but shouldn't that be
bucket_size = (bkt->avg / 10) * bkt->burst_length?
burst_bucket_size = (bkt->avg / 10) / 10;
if !bkt->max then the user didn't define any bursts, and the I/O is only
throttled to the rate set in bkt->avg.
+ } else {
+ /* If we have a burst limit then we have to wait until all I/O
+ * at burst rate has finished before throttling to bkt->avg */
+ bucket_size = bkt->max * bkt->burst_length;
+ burst_bucket_size = bkt->max / 10;
+ }
+
+ /* If the main bucket is full then we have to wait */
+ extra = bkt->level - bucket_size;
because it used to be that if bkt->max is 0 then
extra = bkt->level - (bkt->avg /10) * bkt->burst_length; //fixed value
and now it's
extra = bkt->level - (bkt->avg / 10);
and
if (extra > 0) {
return throttle_do_compute_wait(bkt->avg, extra);
}
- /* If the bucket is not full yet we have to make sure that we
- * fulfill the goal of bkt->max units per second. */
+ /* If the main bucket is not full yet we still have to check the
+ * burst bucket in order to enforce the burst limit */
if (bkt->burst_length > 1) {
- /* We use 1/10 of the max value to smooth the throttling.
- * See throttle_fix_bucket() for more details. */
- extra = bkt->burst_level - bkt->max / 10;
+ extra = bkt->burst_level - burst_bucket_size;
This used to be
extra = bkt->burst_level - (bkt->avg / 10) / 10;
and now it's
extra = bkt->burst_level - 0;
No, if bkt->burst_length > 1 then bkt->max != 0, and therefore
burst_bucket_size is never 0 either.
Perhaps you missed the ! in the first "if (!bkt->max)" ?
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