Re: [9.4 bug] The database server hangs with write-heavy workload on Windows

On 2014-10-09 22:47:48 +0900, MauMau wrote:
> Hello,
>
> One user reported a hang problem with 9.4 beta2 on Windows. The PostgreSQL
> is 64-bit version. I couldn't find the cause, but want to solve the
> problem. Could you help with this?
>
> I heard that the user had run 16 concurrent psql sessions which executes
> INSERT and UPDATE statements, which is a write-intensive stress test. He
> encountered the hang phenomenon twice, one of which occured several hours
> after the start of the test, and the other occured about an hour after the
> test launch.
>
> The user gave me the stack traces, which I attached at the end of this mail.
> The problem appears to be related to the xlog insert scaling. But I can't
> figure out where the root cause lies --- WAL slot handling, spinlock on
> Windows, or PGSemaphoreLock/UnLock on Windows?
>
> The place I suspect is S_UNLOCK(). It doesn't use any memory barrier. Is
> this correct on Intel64 processors?

What precisely do you mean with "Intel64"? 64bit x86 or Itanium?

Also, what's the precise workload? Can you reproduce the problem?

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services