Re: Regression since 53984635a659e360f206a81ada4ae813152d72f1 (drm/i915: use the complete gtt)

[Chris Wilson <chris@chris-wilson.co.uk>]

On Tue, 09 Nov 2010 18:22:48 +0000, Peter Clifton <pcjc2@cam.ac.uk> wrote:
> Since the above commit, my GL app will crash after a period of sustained
> graphics activity. It appears to use quite a lot of small BOs for
> uploading changed VBO data with glBufferSubData, and I don't think these
> are being purged until the GTT is full.
> 
> For some reason, with gtt size != mappable size, the GPU will hang after
> a while. I had thought that we were missing a guard page from
> mappable_size, but subtracting a PAGE_SIZE did not help. Only resetting
> gtt_size to mappable_size (still subtracting a guard page) helped.
> 
> Adding some instrumentation shows:
> 
> Prealloc size 33550336, gtt size 2147479552, mappable size 268435456

/sys/kernel/debug/dri/0/i915_gem_objects

> This is an GM45 on a HP 6730b laptop.
> 
> Any hints as to where to look now?
> 
> Are things being put into unmappable GTT space when they need to be
> mappable?

This is the likely suspect. Check /sys/kernel/debug/dri/0/i915_error_state.

Do you have a test case that I can run? I've been beating upon this using
i945, pnv, q35 and g45 for quite some time and found it to be stable (for
my uses at least).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre