High response time at high concurrent connections

Yichun Zhang (agentzh) agentzh at gmail.com
Tue Oct 1 03:02:34 UTC 2013


On Mon, Sep 30, 2013 at 7:25 AM, laltin wrote:
> But looking at tornado logs I expect around 2000reqs/sec. Assuming that each
> request is handled in 2ms one instance can handle 500reqs/sec and with 4
> instances it sholud be 2000req/sec. But it is stuck at 1200reqs/sec I wonder
> why it is stuck at that point?
> Does increasing the number of instances change the result?

It depends on where the bottleneck really is :)

You can use the on-CPU flamegraph and off-CPU flamegraph tools to
check the on-CPU time and off-CPU time usage by sampling your related
processes under load. In particular, using the following tools on


These tools are very general and not specific to Nginx processes, BTW.

Best regards,

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