Re: stuck spin lock with many concurrent users - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: stuck spin lock with many concurrent users
Date
Msg-id 200107040104.f6414Oc09400@candle.pha.pa.us
Whole thread Raw
In response to Re: stuck spin lock with many concurrent users  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: stuck spin lock with many concurrent users  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
> Yes, it sure is, but remember that the guy getting useful work done
> (DeadLockCheck) is having to share the CPU with 999 other processes
> that are waking up on every clock tick for just long enough to fail
> to get the spinlock.  I think it's those useless process wakeups that
> are causing the problem.
> 
> If you estimate that a process dispatch cycle is ~ 10 microseconds,
> then waking 999 useless processes every 10 msec is just about enough
> to consume 100% of the CPU doing nothing useful... so what should be
> a few-millisecond check takes a long time, which makes things worse
> because the 999 wannabees are spinning for that much more time.

Don't we back off the sleeps or was that code removed?

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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