On Fri, Nov 13, 2015 at 3:46 PM, Christoph Hellwig <hch@xxxxxx> wrote:
The new name is irq_poll as iopoll is already taken. Better suggestions
welcome.
Sagi (or Christoph if you can address that),
@ some pointer over the last 18 months there was a port done at
mellanox for iser to use blk-iopoll and AFAIR it didn't work well or
didn't work at all. Can you tell now what was the problem and how did
you address it at your generalization?
Hi Or,
Sagi mentioned last time he tried a similar approach in iSER he saw
some large latency sparks. We've seen nothing worse than the original
approach. The Flash memory summit slide set has some numbers:
http://www.flashmemorysummit.com/English/Collaterals/Proceedings/2015/20150811_FA11_Bandic.pdf
they aren't quite up to date, but the latency distribution hasn't
really changed.
Or is correct,
I have attempted to convert iser to use blk_iopoll in the past, however
I've seen inconsistent performance and latency skews (comparing to
tasklets iser is using today). This was manifested in IOPs test cases
where I ran multiple threads with higher queue-depth and not in
sanitized pure latency (QD=1) test cases. Unfortunately I didn't have
the time to pick it up since.
I do have every intention of testing it again with this. If it still
exist we will need to find the root-cause of it before converting
drivers to use it.
Sagi.
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