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blockjob: Adhere to rate limit even when reentered early

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When jobs are sleeping, for example to enforce a given rate limit, they
can be reentered early, in particular in order to get paused, to update
the rate limit or to get cancelled.

Before this patch, they behave in this case as if they had fully
completed their rate limiting delay. This means that requests are sped
up beyond their limit, violating the constraints that the user gave us.

Change the block jobs to sleep in a loop until the necessary delay is
completed, while still allowing cancelling them immediately as well
pausing (handled by the pause point in job_sleep_ns()) and updating the
rate limit.

This change is also motivated by iotests cases being prone to fail
because drain operations pause and unpause them so often that block jobs
complete earlier than they are supposed to. In particular, the next
commit would fail iotests 030 without this change.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230510203601.418015-8-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2023-05-10 22:36:00 +02:00
parent 01a10c2433
commit 018e5987b5
5 changed files with 44 additions and 29 deletions
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14
include/block/blockjob_int.h
View file

@ -126,12 +126,18 @@ void block_job_user_resume(Job *job);
*/
/**
* block_job_ratelimit_get_delay:
* block_job_ratelimit_processed_bytes:
*
* Calculate and return delay for the next request in ns. See the documentation
* of ratelimit_calculate_delay() for details.
* To be called after some work has been done. Adjusts the delay for the next
* request. See the documentation of ratelimit_calculate_delay() for details.
*/
int64_t block_job_ratelimit_get_delay(BlockJob *job, uint64_t n);
void block_job_ratelimit_processed_bytes(BlockJob *job, uint64_t n);
/**
* Put the job to sleep (assuming that it wasn't canceled) to throttle it to the
* right speed according to its rate limiting.
*/
void block_job_ratelimit_sleep(BlockJob *job);
/**
* block_job_error_action: