Re: Dynamic LWLock tracing via pg_stat_lwlock (proof of concept)

On Fri, Oct 3, 2014 at 5:51 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> I do think that the instrumentation data gathered by LWLOCK_STATS is
> useful - very useful.

Sure, quite useful.

But how about this comment:
   /*    * The LWLock stats will be updated within a critical section, which    * requires allocating new hash entries.
Allocationswithin a critical    * section are normally not allowed because running out of memory would    * lead to a
PANIC,but LWLOCK_STATS is debugging code that's not normally    * turned on in production, so that's an acceptable
risk.The hash entries    * are small, so the risk of running out of memory is minimal in practice.    */
 


> But it does have significant overhead.

I will say that it is a bit more than overhead for production use.




-- 
Ilya Kosmodemiansky,

PostgreSQL-Consulting.com
tel. +14084142500
cell. +4915144336040
ik@postgresql-consulting.com