many workers threads failed with EAGAIN

Poul-Henning Kamp phk at phk.freebsd.dk
Mon Aug 31 23:41:50 CEST 2009


In message <dcccdf790908310536m155a49cfw770c04657aab1ab6 at mail.gmail.com>, David
 Birdsong writes:
>varnishlog has a lot of these:
> 0 Debug        - "Create worker thread failed 11 Resource temporarily
>unavailable"
>
>sure enough, overflowed and dropped work requests are steadily on the rise
>Hitrate ratio:       10      100     1000
>Hitrate avg:     0.8584   0.8506   0.8581

>        1007          .            .   N worker threads
>        1007         0.00         0.34 N worker threads created
>       12425         4.00         4.20 N worker threads not created
>        2002         1.00         0.68 N queued work requests
>      651706       157.04       220.47 N overflowed work requests
>      460396       262.07       155.75 N dropped work requests

It is not clear to me why you ended up needing so many threads,
but the usualy explanation is comms problems either in client
or backend direction.

If you have not enabled backend probing, you should do so, since that
prevents the threads from getting stuck on a troubled backend.

Poul-Henning

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.



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