Lots of CPU going in Channel.write() (Yourkit profile attached)

[Trustin Lee (이희승)]

Hi Utkarsh,

Thanks for reporting this issue.

I've just checked in a tiny modification that reduces the number of
Channel.isConnected() calls.  Could you test the latest build and let
me know how it looks like now?

   http://trustin.dyndns.org/hudson/job/netty-trunk-deploy/111/

— Trustin Lee, http://gleamynode.net/



On Mon, Sep 14, 2009 at 1:30 AM, Utkarsh Srivastava <utkarsh at gmail.com> wrote:
> Retrying ...
> Did anyone get a chance to look at this profile?
> I think there are real opportunities to optimize this code path in netty
> based on the profile attached. Channel.write() should not be taking up so
> much CPU.
> Utkarsh
>
> On Thu, Sep 10, 2009 at 11:37 PM, Utkarsh Srivastava <utkarsh at gmail.com>
> wrote:
>>
>> Hi,
>> I recently rewrote an application that was not using Netty (or even NIO)
>> so as to use Netty. Netty has been great to use, the API, the doc,
>> everything. Thanks for the good work.
>> Using netty 3.1.2.GA, my application basically blasts out messages to 2
>> servers. I would expect to be able to saturate the network pipe. I am able
>> to do so at larger message sizes (e.g. 16K).
>> But for small messages (e.g. 1K), the application doesn't saturate the
>> network but becomes CPU bound. I profiled the application using Yourkit and
>> one place that I noticed that had a high CPU consumption but shouldn't was
>> channel.write().
>> The breakdown of that method is attached. What is strange is 19% of the
>> time going in NioClientSocketPipelineSink.eventSunk() and its own time is
>> nontrivial (170 ms = 7%). Looking at the code, I don't see any place where
>> that CPU can be spent (since NIOWorker.write() and
>> NIOSocketChannel$WriteBuffer.offer() have their own separate contributions
>> of 9 and 3% respectively. So this is extremely puzzling. Anybody have
>> thoughts on this?
>> Also, is it necessary to make that system call every time to check if the
>> channel is connected? That alone is taking up 6%.
>> Thanks
>> Utkarsh
>>
>
>
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