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Date: Wed, 25 Oct 2006 16:18:51 -0400
From: Brian Hurt <bhurt@janestcapital.com>
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To: Carlo Stonebanks <stonec.register@sympatico.ca>
Cc: pgsql-performance@postgresql.org
Subject: Re: commit so slow program looks frozen
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Carlo Stonebanks wrote:

>>You may try to figure out what's the process doing (the backend
>>obviously, not the frontend (Tcl) process) by attaching to it with
>>strace.
>>    
>>
>
>It's so sad when us poor Windows guys get helpful hints from people assume 
>that we're smart enough to run *NIX... ;-)
>
>  
>
>>Maybe it's swamped by a context switch storm (but in that case, probably 
>>the other processes would be affected as well).
>>    
>>
>
>What is a context switch storm? (and what a great name for a heavy metal 
>rock band!)
>
>Interestingly enough, last night (after the original post) I watched three 
>of the processes slow down, one after the other - and then stall for so long 
>that I had assumed they had frozen. They were all stalled on a message that 
>I had put in the script that indicated they had never returned from a 
>commit. I have looked into this, and I believe the commits are actually 
>going through.
>  
>
I have a question for you: did you have a long running query keeping 
open a transaction?  I've just noticed the same problem here, but things 
cleaned up immediately when I aborted the long-running transaction.

Note that in my case the long-running transaction wasn't idle in 
transaction, it was just doing a whole lot of work.

Brian


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Carlo Stonebanks wrote:<br>
<blockquote cite="midehog68$19d3$1@news.hub.org" type="cite">
  <blockquote type="cite">
    <pre wrap="">You may try to figure out what's the process doing (the backend
obviously, not the frontend (Tcl) process) by attaching to it with
strace.
    </pre>
  </blockquote>
  <pre wrap=""><!---->
It's so sad when us poor Windows guys get helpful hints from people assume 
that we're smart enough to run *NIX... ;-)

  </pre>
  <blockquote type="cite">
    <pre wrap="">Maybe it's swamped by a context switch storm (but in that case, probably 
the other processes would be affected as well).
    </pre>
  </blockquote>
  <pre wrap=""><!---->
What is a context switch storm? (and what a great name for a heavy metal 
rock band!)

Interestingly enough, last night (after the original post) I watched three 
of the processes slow down, one after the other - and then stall for so long 
that I had assumed they had frozen. They were all stalled on a message that 
I had put in the script that indicated they had never returned from a 
commit. I have looked into this, and I believe the commits are actually 
going through.
  </pre>
</blockquote>
I have a question for you: did you have a long running query keeping
open a transaction?&nbsp; I've just noticed the same problem here, but
things cleaned up immediately when I aborted the long-running
transaction.<br>
<br>
Note that in my case the long-running transaction wasn't idle in
transaction, it was just doing a whole lot of work.<br>
<br>
Brian<br>
<br>
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