#235: Varnish Linux performance
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Reporter: rafaelumann | Owner: phk
Type: defect | Status: new
Priority: high | Milestone:
Component: varnishd | Version: trunk
Severity: normal | Keywords: performance
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Hi,
### Situation:
We are using Quad Xeon 3Ghz HT servers in our production environment, and
one varnish thread makes one CPU usage goes to 0% free.
Process strace repeats:
clock_gettime(CLOCK_MONOTONIC, {431276, 305144924}) = 0
epoll_wait(12, {{EPOLLIN, {u32=1371080556, u64=1371080556}}}, 1, 100) = 1
read(139, "GET /ads//i/bv1024/bv_ml07_v2.pn"..., 4095) = 403
epoll_ctl(12, EPOLL_CTL_DEL, 139, {0, {u32=0, u64=0}}) = 0
write(4002, "\317", 1) = 1
This process seems to be the responsible for distributing connections
between threads and clean the timeout sockets.
The problem possibly happens because this process tries to cleanup the
timeout sockets each new connection.
### Kernel:
Kernel: 2.6.18-53.el5PAE
### Solution:
First we tried to use the same code used in varnish for freebsd (kqueue),
that just searches for sockets with "dotimer=1" to clean timeout sockets,
but it didn't work out because there are too many connections that would
never be cleaned, and so too many sockets stayed opened.
So, as a work around, I annexed a firsthand patch for test, that just add
a "timeout counter" and cleans the timeout sockets every 60 seconds
instead of cleaning it in every new connection received. We are using it
here, and the performance is much better now.
In the trunk or 1.1.2 version varnish doesn't go further than 4000 "Client
requests received" with real traffic, but it goes much longer with Apache
Benchmark traffic. While in our patched version we easily get to "8197.18"
"Client requests received", without AB.
Anyway, we don't think that this should be the final solution. Maybe a new
thread to cleanup the timeout sockets will be a better solution.
[]s,
Rafael Umann
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Ticket URL: <http://varnish.projects.linpro.no/ticket/235>
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