Re: stuck spin lock with many concurrent users

> Tatsuo Ishii <t-ishii@sra.co.jp> writes:
> > I have seen problems with extremely many concurrent users.
> > I run pgbench:
> 
> > pgbench -c 1000 -t 1 test
> 
> > And I get stuck spin lock errors. This is 100% reproducable (i.e. I
> > have nerver succeeded in pgbench -c 1000).
> 
> Is it actually stuck, or just timing out due to huge contention?
> You could try increasing the timeout intervals in s_lock.c to
> make sure.  

I believe it's an actual stuck. From s_lock.c:

#define DEFAULT_TIMEOUT (100*1000000)    /* default timeout: 100 sec */

So even if there are 1000 contentions, 100 sec should be enough (100
msec for each backend).

> If it is stuck, on which lock(s)?

How can I check it? In that situation, it's very hard to attacth a
debugger to the backend process. 1000 backends consum all CPU time.
--
Tatsuo Ishii