Massive apache slowdown after high load period

[Robert Watson]

On Thu, 22 Jun 2006, Steven Hartland wrote:

> We've just had a box which was subjected to a large amount of small apache 
> requests once this subsided the response of apache was still very slow. Many 
> seconds between requests showing in tcpdump and response being returned.
>
> Upon investigation it seemed the number of sockets in teardown / mbufs 
> allocated might be the cause has anyone else experienced that?

On 5.x SMP systems, there is a known problem in mbuf memory statistics 
reporting, which has been corrected in 6.x.  The below mbuf counter is 
probably a property of that known problem, and is likely unrelated to the 
slowdown you have experienced.

Robert N M Watson
Computer Laboratory
University of Cambridge

>
> netstat -m
> 4294880568 mbufs in use
> 29885/76800 mbuf clusters in use (current/max)
> 0/5/6656 sfbufs in use (current/peak/max)
> 38088 KBytes allocated to network
> 0 requests for sfbufs denied
> 0 requests for sfbufs delayed
> 0 requests for I/O initiated by sendfile
> 687 calls to protocol drain routines
>
> netstat showed
>  1 CLOSE_WAIT
>  6 LAST_ACK
> 41 FIN_WAIT_1
> 129 FIN_WAIT_2
> 295 ESTABLISHED
> 1083 TIME_WAIT
>
> A restart of apache made no difference a reboot
> of the machine was required to return normal
> performance.
>
> N.B. 5.4-RELEASE-p8 is in use on the machine in
> question.
>
>   Steve
>
>
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