March 08, 2010 11:04PM
Again more information:

When my benchmarks aren't running, I can receive via wget a
single file at 50megabyte/s from one of my benchmark clients.
Note this is not part of my nginx benchmark, I am just showing
my nginx server can receive 50mbyte/s throughput no problem.

Now, when my benchmark clients are running httperf against
the server, there is a max of 8megabyte/s throughput and
there is approx. 1500 concurrent connections open:

# cat /proc/net/sockstat
TCP: inuse 1466 orphan 26 tw 0 alloc 1467 mem 12544
UDP: inuse 3
RAW: inuse 0
FRAG: inuse 0 memory 0

This is when nginx (or the OS) becomes slow to start
serving new connections.

I tried just now, downloading the test file to my server while the
benchmark is running. This is the file I can usually receive at
50megabyte/s. I straced wget and it first hangs in poll()
trying to lookup the hostname. It retries a few times and after
about 5-10 seconds it begins downloading but only at 13
kilobyte/s.

So, it's not a problem of throughput saturation. I don't believe
it's because of any limits like file descriptors, somaxconn or
rmem/wmem, as I have maxed those (and tried them at
smaller values too.) CPU is 97-98% idle the entire time and
there is no waiting on disk.

I honestly have no idea what can be causing this! Any advice
would be very much appreciated.

Steve
Subject Author Posted

Performance plateau when keepalives enabled

powderhound March 08, 2010 11:30AM

Re: Performance plateau when keepalives enabled

Maxim Dounin March 08, 2010 05:10PM

Re: Performance plateau when keepalives enabled

powderhound March 08, 2010 05:21PM

Re: Performance plateau when keepalives enabled

powderhound March 08, 2010 06:15PM

Re: Performance plateau when keepalives enabled

powderhound March 08, 2010 06:42PM

Re: Performance plateau when keepalives enabled

powderhound March 08, 2010 09:35PM

Re: Performance plateau when keepalives enabled

powderhound March 08, 2010 11:04PM

Re: Performance plateau when keepalives enabled

James Matthews March 08, 2010 06:10PM

Re: Performance plateau when keepalives enabled

James Matthews March 08, 2010 06:36PM

Re: Performance plateau when keepalives enabled

Momchil Ivanov March 11, 2010 08:28AM

Re: Performance plateau when keepalives enabled

Vinay Y S March 21, 2010 04:30AM



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