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Re: [PATCH 1/9] move blk_iopoll to limit and make it generally available

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>> On Fri, Nov 13, 2015 at 3:46 PM, Christoph Hellwig <hch@lst.de> 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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Thread

add a proper completion queue abstraction Christoph Hellwig <hch@lst.de> - 2015-11-13 15:00 +0100
  [PATCH 7/9] IB/iser: Use a dedicated descriptor for login Christoph Hellwig <hch@lst.de> - 2015-11-13 15:00 +0100
  [PATCH 1/9] move blk_iopoll to limit and make it generally available Christoph Hellwig <hch@lst.de> - 2015-11-13 15:00 +0100
    Re: [PATCH 1/9] move blk_iopoll to limit and make it generally available Or Gerlitz <gerlitz.or@gmail.com> - 2015-11-13 16:30 +0100
      Re: [PATCH 1/9] move blk_iopoll to limit and make it generally  available Christoph Hellwig <hch@lst.de> - 2015-11-14 08:10 +0100
        Re: [PATCH 1/9] move blk_iopoll to limit and make it generally  available Sagi Grimberg <sagig@dev.mellanox.co.il> - 2015-11-15 09:50 +0100
          Re: [PATCH 1/9] move blk_iopoll to limit and make it generally available Or Gerlitz <gerlitz.or@gmail.com> - 2015-11-15 10:10 +0100
            Re: [PATCH 1/9] move blk_iopoll to limit and make it generally  available Sagi Grimberg <sagig@dev.mellanox.co.il> - 2015-11-15 14:20 +0100
          Re: [PATCH 1/9] move blk_iopoll to limit and make it generally  available Christoph Hellwig <hch@lst.de> - 2015-11-15 14:00 +0100
    Re: [PATCH 1/9] move blk_iopoll to limit and make it generally  available Christoph Hellwig <hch@lst.de> - 2015-11-14 08:10 +0100
      Re: [PATCH 1/9] move blk_iopoll to limit and make it generally  available Christoph Hellwig <hch@lst.de> - 2015-11-18 15:00 +0100
  [PATCH 6/9] srp: use the new CQ API Christoph Hellwig <hch@lst.de> - 2015-11-13 15:00 +0100
    Re: [PATCH 6/9] srp: use the new CQ API Christoph Hellwig <hch@lst.de> - 2015-11-18 15:10 +0100
  [PATCH 4/9] srpt: chain RDMA READ/WRITE requests Christoph Hellwig <hch@lst.de> - 2015-11-13 15:00 +0100
    Re: [PATCH 4/9] srpt: chain RDMA READ/WRITE requests Sagi Grimberg <sagig@dev.mellanox.co.il> - 2015-11-18 10:20 +0100
      Re: [PATCH 4/9] srpt: chain RDMA READ/WRITE requests Christoph Hellwig <hch@lst.de> - 2015-11-20 11:30 +0100
    Re: [PATCH 4/9] srpt: chain RDMA READ/WRITE requests Christoph Hellwig <hch@lst.de> - 2015-11-18 15:10 +0100
  [PATCH 9/9] IB/iser: Convert to CQ abstraction Christoph Hellwig <hch@lst.de> - 2015-11-13 15:00 +0100
  [PATCH 8/9] IB/iser: Use helper for container_of Christoph Hellwig <hch@lst.de> - 2015-11-13 15:00 +0100

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