Re: read() syscall slowing down due to other threads?

From: George Porter
Date: Tue May 15 2012 - 17:08:57 EST

Thanks for the response--we did play around with core affinity, and it
does make a difference for sure. The major thing was turning off HP's
power management stuff, and putting the BIOS into high-performance
mode. That helped a lot.

Thanks, George

On Wed, May 2, 2012 at 11:39 AM, Chris Friesen
<chris.friesen@xxxxxxxxxxx> wrote:
> On 05/01/2012 12:03 AM, George Porter wrote:
>> However, if I start doing more computation on those other threads, the
>> read() syscalls take longer to read the same amount of data,
>> eventually slowing down to 50 MBps (50% slower).  I've used
>> setaffinity() to isolate the Reader threads to one set of cores, and
>> the compute threads to a different set of cores, and so I don't think
>> it is CPU/scheduling interference.
>> Thoughts?  Has anyone run into this before?
> If you're using hyperthreading you may want to try it with either putting
> the computation threads on the siblings of the cpus for the reader threads
> (to share cache) or else not on the siblings of the cpus for the reader
> threads (to minimize contention of cpu resources).
> Similarly, you may want to play with wither or not the threads are on the
> same or different sockets.
> Chris
> --
> Chris Friesen
> Software Developer
> chris.friesen@xxxxxxxxxxx
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