[Intel-gfx] Regression since 53984635a659e360f206a81ada4ae813152d72f1 (drm/i915: use the complete gtt)

Chris Wilson chris at chris-wilson.co.uk
Tue Nov 9 19:56:40 CET 2010

On Tue, 09 Nov 2010 18:22:48 +0000, Peter Clifton <pcjc2 at 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


> 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 Wilson, Intel Open Source Technology Centre

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