Re: Integration of SCST in the mainstream Linux kernel

Bart Van Assche
2008-01-30T16:51:13Z

On Jan 30, 2008 5:34 PM, James Bottomley
<James.Bottomley@hansenpartnership.com> wrote:
>
> On Wed, 2008-01-30 at 09:38 +0100, Bart Van Assche wrote:
> > On Jan 30, 2008 12:32 AM, FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
> > >
> > > iSER has parameters to limit the maximum size of RDMA (it needs to
> > > repeat RDMA with a poor configuration)?
> >
> > Please specify which parameters you are referring to. As you know I
> > had already repeated my tests with ridiculously high values for the
> > following iSER parameters: FirstBurstLength, MaxBurstLength and
> > MaxRecvDataSegmentLength (16 MB, which is more than the 1 MB block
> > size specified to dd).
>
> the 1Mb block size is a bit of a red herring. Unless you've
> specifically increased the max_sector_size and are using an sg_chain
> converted driver, on x86 the maximum possible transfer accumulation is
> 0.5MB.

I did not publish the results, but I have also done tests with other
block sizes. The other sizes I tested were between 0.1MB and 10MB. The
performance difference for these other sizes compared to a block size
of 1MB was small (smaller than the variance between individual tests
results).

Bart.