Conditional locking in pgaio_worker_submit_internal With io_method=worker, there's a single I/O submission queue. With enough workers, the backends and workers may end up spending a lot of time competing for the AioWorkerSubmissionQueueLock lock. This can happen with workloads that keep the queue full, in which case it's impossible to add requests to the queue. Increasing the number of I/O workers increases the pressure on the lock, worsening the issue.
This change improves the situation in two ways: * If AioWorkerSubmissionQueueLock can't be acquired without waiting, the I/O is performed synchronously (as if the queue was full). * When an entry can't be added to a full queue, stop trying to add more entries. All remaining entries are handled as synchronous I/O. The regression was reported by Alexandre Felipe. Investigation and patch by me, based on an idea by Andres Freund. Reported-by: Alexandre Felipe <[email protected]> Author: Tomas Vondra <[email protected]> Reviewed-by: Andres Freund <[email protected]> Discussion: https://postgr.es/m/cae8jnxon4+xuance+m7lfzwoqfrmmxasmaemskwikbqtzr6...@mail.gmail.com Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/29a0fb215779d10fae0cbeb8ce57805f244bad9b Modified Files -------------- src/backend/storage/aio/method_worker.c | 57 ++++++++++++++++++++------------- 1 file changed, 34 insertions(+), 23 deletions(-)
