Messages in this thread | | | Subject | Re: Integration of SCST in the mainstream Linux kernel | From | James Bottomley <> | Date | Wed, 30 Jan 2008 10:34:31 -0600 |
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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 certainly don't rule out that increasing the transfer size up from 0.5MB might be the way to improve STGT efficiency, since at an 1GB/s theoretical peak, that's roughly 2000 context switches per I/O; however, It doesn't look like you've done anything that will overcome the block layer limitations.
James
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