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

[Trustin Lee (이희승)]

Hi Utkarsh,

The modification I made is permanent.  I skipped calling isConnected()
because trying to write something on a closed channel raises
ClosedChannelException anyway.  There was no need to double-check - OS
(or JDK) checks before actually writing.

Thanks for suggestion, and it's nice to see better performance. :)

Cheers

— Trustin Lee, http://gleamynode.net/


On Tue, Sep 22, 2009 at 5:01 AM, Utkarsh Srivastava <utkarsh at gmail.com> wrote:
> Hi Trustin,
> I tested the new build and the results are awesome. Throughput is way up (at
> least a 30% jump for 1K messages) and CPU utilization is way down. People
> who have benchmarked Netty previously should re-run their benchmarks.
> On the cautious side, I noticed that in the patch, you just omitted the call
> to channel.isConnected(). Is that a long-term solution or just a stop-gap?
> When are you planning to put this into maven so that our builds can pick it
> up?
> Thanks
> Utkarsh
>
> On Sun, Sep 20, 2009 at 7:11 PM, Trustin Lee (이희승) <trustin at gmail.com>
> wrote:
>>
>> 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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>> >
>>
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