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

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Message-ID: <CANkdjvYL8cne9xmgjFcFDbn74ss6WzXTDXY34f_MWcsaDKeTDg@mail.gmail.com>
Date:	Tue, 15 May 2012 14:08:42 -0700
From:	George Porter <gmporter@...ucsd.edu>
To:	Chris Friesen <chris.friesen@...band.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: read() syscall slowing down due to other threads?

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@...band.com> 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
> GENBAND
> chris.friesen@...band.com
> www.genband.com
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