[Ace-users] [ace-users] Using ACE_Svc_Handler::msg_queue() for buffering is slow
Douglas C. Schmidt
schmidt at dre.vanderbilt.edu
Sun Nov 4 12:30:19 CST 2007
>If I limit the size of the message block to 10 bytes, and I want to
>send 8192 bytes to the server: the send command will be called once
>with 10 bytes, then again pulling the remaining data off the message
>queue to send 8182 bytes.
Ah, it sounds like you're running into Nagel's algorithm. If you
disable this by enabling TCP_NODELAY then your performance should be
much better. Please see chapter 3 of C++NPv1
<www.cs.wustl.edu/~schmidt/ACE/book1/> for details on this.
> (provided the client is ready to receive it
>all, which it almost always is).
>If I comment out the code that uses the message block so it always
>goes to into the queue, send will be called with 8192 bytes.
>If I force the message block to 8192 bytes, send will again be called
>with 8192 bytes.
>The above approaches take the same amount of time, in fact the time
>spent inside the handle_output function for a test run sending
>10megabytes is less than a second. In the first two approahces, the
>entire 10megs will take at least 2 minutes to send. Only in the final
>case, the entire 10 megs will take about 2 seconds to send.
>As far as I can tell profiling the program, next to no time is
>actually being spent inside the code, it seems to be spending most of
>it's time waiting. I almost suspect that putting thins in the Message
>queue is somehow interacting with the reactor in a way to slow down
>event dispatching. My next step is probably going to be putting
>Message Blocks in a std::queue rather than the ACE one.
>On Nov 4, 3:38 pm, schm... at dre.vanderbilt.edu (Douglas C. Schmidt)
>> >None, i.e. ACE_NULL_MUTEX
>> Ok, great. One more question - what's the size of the data that
>> you're sending with each approach, i.e., are you sending an 8k
>> buffer at one time with the first approach and 10 byte buffers at a
>> time with the other? I recommend you use strace or ethereal to see
>> what's going on wrt the data entering/leaving your machine.
>> On Nov 3, 11:59 pm, schm... at dre.vanderbilt.edu (Douglas C. Schmidt)
>> >> Hi,
>> >> > No, it uses the reactor the same amount. The ACE_Message_Queue is
>> >> > used as a fallback if the ACE_Message_Block gets full. If the
>> >> > 'buffer gets full it just puts all the data in the queue, when
>> >> > handle_output is called it sends all the data it can from both the
>> >> > buffer and the queue. handle_output is called the same number of
>> >> > times regardless of method used.
>> >> Ok, so what type of synchronization are you using for the ACE_Message_Queue?
>> >> Thanks,
>> >> Doug
>> >> --
>> >> Dr. Douglas C. Schmidt Professor and Associate Chair
>> >> Electrical Engineering and Computer Science TEL: (615) 343-8197
>> >> Vanderbilt University WEB:www.dre.vanderbilt.edu/~schmidt
>> >> Nashville, TN 37203 NET: d.schm... at vanderbilt.edu
>> Dr. Douglas C. Schmidt Professor and Associate Chair
>> Electrical Engineering and Computer Science TEL: (615) 343-8197
>> Vanderbilt University WEB:www.dre.vanderbilt.edu/~schmidt
>> Nashville, TN 37203 NET: d.schm... at vanderbilt.edu
Dr. Douglas C. Schmidt Professor and Associate Chair
Electrical Engineering and Computer Science TEL: (615) 343-8197
Vanderbilt University WEB: www.dre.vanderbilt.edu/~schmidt
Nashville, TN 37203 NET: d.schmidt at vanderbilt.edu
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