[httperf] fd-unavail non-null

Sylvain Geneves sylvain.geneves at inrialpes.fr
Fri Sep 3 10:09:18 PDT 2010


On 09/02/2010 08:36 PM, Rick Jones wrote:
>> *) I'll try that but i'm not sure how the OS will behave when
>> assigning multiple IPs to a single NIC
>
> It should behave just fine. Support for multiple IPs per NIC has been in
> almost every TCP/IP stack out there for years.
>
>> *) I fear that assigning more than one IP to a single NIC on the
>> server will stress the network load-balancing algorithm of the OS too
>> much
>
> How so?
>
In my previous experience, when using the Linux NIC bonding system to 
assign more than one IP per NIC, we weren't able to achieve full network 
performance.
That's why I think that even if doing this on the clients is fine, it 
could add a significan overload on the server, because it has much more 
networking to deal with.
But that's just thoughts and I haven't tested that configuration in this 
precise case.

>> actually I tuned TCP parameters for my tests, and after chechking that
>> it turns out that TIME_WAIT is dramatically reduced to 1sec in my
>> configuration, so I'm surprised this problem arises this fast (seems
>> to be any rate above 1000sess/sec).
>

come to think of it, it's not surprising at all : since of my client 
machines have eight cores, I naively launched 8 httperf instances on 
each one.
Since I was having fd-unavail errors (EMFILE), which means per-process 
errors instead of ftab-full (ENFILE), which are system-wide, I didn't 
realise it could be the cause of my problems in the first place.

using more machines with 4 httperf instances allows me to bench higher 
rates.

anyway thanks for your help!


> rick jones
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> httperf at linux.hpl.hp.com
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