Re: BUG: Slowdown on 3000 socket-machines tracked down

[Ben Greear <greearb@candelatech.com>]

Nick Piggin wrote:
> Ben Greear wrote:
> 
>> Christian Schmid wrote:
>>
>>> Ben Greear wrote:
> 
> 
>>>> How many bytes are you sending with each call to write()/sendto() 
>>>> whatever?
>>>
>>>
>>>  
>>> I am using sendfile-call every 100 ms per socket with the poll-api. 
>>> So basically around 40 kb per round.
>>
>>
>>
>> My application is single-threaded, uses non-blocking IO, and 
>> sends/rcvs from/to memory.
>> It will be a good test of the TCP stack, but will not use the sendfile 
>> logic,
>> nor will it touch the HD.
>>
> 
> I think you would have better luck in reproducing this problem if you
> did the full sendfile thing.
> 
> I think it is becoming disk bound due to page reclaim problems, which
> is causing the slowdown.
> 
> In that case, writing the network only test would help to confirm the
> problem is not a networking one - so not useless by any means.

It's not trivial to write something like this :)

I'll be using something I already have.  If I can't reproduce the problem,
then perhaps it is due to sendfile and someone can write a customized
test.  The main reason I offered is because people are ignoring the
bug report for the most part and asking for a test case.  I may be able
to offer an independent verification of the problem which might convince
someone to write up a dedicated test case...

Ben


-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com