[ofa-general] RE: [Scst-devel] SRP aggregate bandwidth decreasing as threads increase

[Bart Van Assche]

On Mon, May 18, 2009 at 6:52 PM, Sufficool, Stanley
<ssufficool at rov.sbcounty.gov> wrote:
> IIRC, The SRP Target code has many context switches that throttle
> performance at higher thread counts.

Depends on which version of ib_srpt you are using. The ib_srpt kernel
module has a parameter called "thread" which allows to control whether
disk I/O is handled in another thread than the one that communicates
over InfiniBand (thread=1) or in the same thread (thread=0). For older
versions of the ib_srpt kernel module the default was thread=1, which
caused indeed a lot of context switches. On December 3, 2008 (SCST
Subversion revision 594) the default has been changed from thread=1 to
thread=0 because the latter results in better performance.

Bart.