[Intel-gfx] [PATCH 0/6] Page faults to help user space debug

[Ben Widawsky]

On Sat, Jun 29, 2013 at 04:38:00PM +0200, Daniel Vetter wrote:
> On Sat, Jun 29, 2013 at 12:23 AM, Ben Widawsky <ben at bwidawsk.net> wrote:
> > 2. echo 2 > /sys/kernel/debug/dri/0/i915_debug_flags
> > Unbind all buffers synchronously, so any batch which has bad code will fault
> > every time and not get lucky by hitting a buffer it bound. This will not catch
> > cases where it accidentally reads/writes someone else's buffer.
> 
> We already have this as the drop_caches debugfs interface. Chris used
> it to reproduce the 3.7 reloc-tree regression, the only downside is
> that no one ever got around to write the respective i-g-t ... :(
> -Daniel

In order to achieve the same behavior, one must instrument every GPU
client to use that interface before, and after every batch (you can skip
one if you're positive all clients have opted in). Also, every client
must be run as root.

This mechanism I've introduced is much simpler to achieve the intended
result.

> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch

-- 
Ben Widawsky, Intel Open Source Technology Center