Reducing overflowed and dropped work requests
sime at sime.net.au
Thu Jul 14 14:18:44 CEST 2011
The Varnish munin plugins have alerted me a number of times (say less
then 5) that N dropped work requests (n_wrk_drop) is greater then 1.
According to Kristian Lyngstol's post  this is represents when the
request queue it full. Additionally I believe the overflowed work
requests (n_wrk_overflow) will always be greater then n_wrk_drop.
I think I should be trying to tackle two issues: Limit requests
overflowing, followed by increasing the size of the request queue.
Of the below startup parameters I believe thread_pools should match
the number of cores the server has and increase the maximum number of
threads to possibly double (from 25 to 50?).
DAEMON_OPTS="-a :80 \
-T localhost:6082 \
-f /etc/varnish/default.vcl \
-S /etc/varnish/secret \
-w 10,25,120 \
-p listen_depth=8192 \
-p log_hashstring=off \
-p lru_interval=60 \
-p sess_timeout=10 \
-p shm_workspace=32768 \
-p ping_interval=1 \
-p thread_pools=4 \
Varnish 2.1.5, x86_64, 4 GB, 8 or 16 cores.
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