[Intel-gfx] [PATCH] RFC drm/i915: Slaughter the thundering i915_wait_request herd

[Gong, Zhipeng]

It seems that there are some gaps in the patch and first patch. 
Like there is no this line in the first patch. 
      if (req->ring->seqno_barrier)

I have tried to apply this patch. And here is the cpu utilization and perf data on BDW

CPU util      |	w/o patch  |   w/ patch
----------------------------------------------------------
BDW async 1   |   116%     |     95%
BDW async 5   |   111%     |     91%

> -----Original Message-----
> From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
> Sent: Tuesday, November 03, 2015 4:59 AM
> To: Gong, Zhipeng; intel-gfx at lists.freedesktop.org; Rogozhkin, Dmitry V
> Subject: Re: [Intel-gfx] [PATCH] RFC drm/i915: Slaughter the thundering
> i915_wait_request herd
> 
> On Mon, Nov 02, 2015 at 03:28:22PM +0000, Chris Wilson wrote:
> > That should keep the worker alive for a further 10 jiffies, hopefully
> > long enough for the next wait to occur. The cost is that it keeps the
> > interrupt asserted (and to avoid that requires a little rearrangment
> > and probably a dedicated kthread for each ring).
> 
> Slightly better version that avoids keeping the interrupt active when not
> required:
> 
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