AW: Varnish VMods for Version 6.1?

Winkelmann, Thomas (RADIO TELE FFH - Online) t.winkelmann at
Fri Sep 21 11:50:43 UTC 2018

I again did some testing by settings the params to

-p thread_pools=4
-p thread_pool_min=2000
-p thread_pool_max=5000
-p thread_pool_reserve=95

The document says that thread_pool_reserve is a value from 0 to 95. It's working fine on one of our two servers which have less load (300 req/s) than the primaray one (> 800req/s).

On the primary one you can see decreasing the client.req in varnishstat two seconds after restarting hitch with H/2 enabled. It jumps from 100req/s to 1700req/s from one second to the next.

-----Ursprüngliche Nachricht-----
Von: Dridi Boukelmoune [mailto:dridi at]
Gesendet: Freitag, 21. September 2018 10:56
An: Winkelmann, Thomas (RADIO TELE FFH - Online)
Cc: varnish-misc
Betreff: Re: Varnish VMods for Version 6.1?

On Thu, Sep 20, 2018 at 3:51 PM Winkelmann, Thomas (RADIO TELE FFH -
Online) <t.winkelmann at> wrote:
> Just tested these values. Varnish is nearly dead after restarting with these new values. Only a few requests will be served. I think, we have to wait :)

I guess now would be a good time to bring back h2load. If you increase
thread_pool_min to 2000 (a value that shouldn't be unreasonable) that
brings the thread_pool_reserve to 400, so even if I didn't bump it further
to 500 it'd be in the same ballpark. And if that is enough to bring Varnish
to a crawl we may have a deeper problem here.

As a general rule of thumb we recommend a thread_pool_min sized for
high (for a given definition of high, let's say above average) traffic so that
sudden peaks of traffic wouldn't wait too long for threads to be created.

I don't see why that should become a problem with Varnish 6 :-/


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