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

Christoph Hellwig
2015-11-14T07:02:05Z

On Fri, Nov 13, 2015 at 05:23:39PM +0200, Or Gerlitz wrote:
> 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.