Re: [PATCH 18/29] drm/i915: Use new bind/unbind in eviction code

Ben Widawsky
2013-08-07T18:24:29Z

On Wed, Aug 07, 2013 at 01:44:58AM +0200, Daniel Vetter wrote:
> On Wed, Aug 7, 2013 at 1:25 AM, Ben Widawsky <ben@bwidawsk.net> wrote:
> > On Wed, Aug 07, 2013 at 12:59:29AM +0200, Daniel Vetter wrote:
> >> On Wed, Aug 7, 2013 at 12:57 AM, Ben Widawsky <ben@bwidawsk.net> wrote:
> >> >> > We need evict_everything for #1. For #2, we call evict_something already
> >> >> > for the vm when we go through the out of space path. If that failed,
> >> >> > evicting everything for a specific VM is just the same operation. But
> >> >> > maybe I've glossed over something in the details. Please correct if I'm
> >> >> > wrong. Is there a case where evict something might fail with ENOSPC, and
> >> >> > evict everything in a VM would help?
> >> >>
> >> >> Yes, when we've terminally fragmented the gtt we kick out everything and
> >> >> start over. That's the 3rd usecase.
> >> >
> >> > I am not seeing it. To me evict_something is what you want, and the fix
> >> > for wherever the 3rd usecase is (please point it out, I'm dense) is it
> >> > should call evict_something, not evict_everything.
> >>
> >> See the call to evict_everything in
> >> i915_gem_execbuffer.c:i915_gem_execbuffer_reserve
> >>
> >
> > As I was saying in the first response - you only hit this if
> > evict_something() for a vm fails, right? That's the way ret == ENOSPC
> > AFAICT.
>
> Like I've said if we can't fit a batch we do a last ditch effort of
> evicting everything and starting over anew. That's also what the retry
> logic in there is for. This happens after evict_something failed.
> Dunno what exactly isn't clear or what's confusing ...
> -Daniel

Okay, sorted this out on IRC. You'll get a new patch as described with a
new function for per vm eviction (which will just idle, and call
evict_something() with proper args)

--
Ben Widawsky, Intel Open Source Technology Center