Reducing overflowed and dropped work requests

[Tollef Fog Heen]

]] Simon Males 

| Since this post, I increased the thread_pools to 8, though today I've
| had another spurt of dropped work requests. It's definitely related to
| a sudden rise of traffic, as the dropped requests happen moment after
| sending an E-Mail to our users.
| 
| The servers have 16 cores, so I've increased the thread_pools to 16
| now. With 10 minimum threads per pool, I now have 160 threads waiting
| to serve.

If you're on 2.1 you might want to set thread_pool_add_delay to 2 (ms)
or similar.  It's set a bit too high there, which means it takes a
little while for Varnish to respond to rapid spikes.

-- 
Tollef Fog Heen
Varnish Software
t: +47 21 98 92 64