[Intel-gfx] Fwd: __i915_gem_shrink / mm_find_pmd hogging CPU, then out of memory

[Chris Wilson]

On Mon, Jun 02, 2014 at 02:18:14PM +0100, Sam Jansen wrote:
>    Hello intel-gfx,
>    I'm working on an application using VA-API for H264 encode+decode, and
>    JPEG decode on an Atom E3815. Unfortunately we've hit what I believe is a
>    kernel bug, and the "perf top" output is pointing at i915 DRM code.
>    After some amount of time running my application, the system will become
>    unresponsive (userspace applications get very little CPU, system CPU will
>    go up to 80+%), and sometimes the system will appear out of memory for a
>    period (the OOM killer is sometimes invoked), even though there is a lot
>    of free memory on the system. I noticed this first on kernel 3.14.5, so I
>    moved to "drm-intel-nightly", built on Friday (2014-05-30), from
>    [1]http://cgit.freedesktop.org/drm-intel. The results are the same.
>    Using "perf top", I have gathered the following traces showing high system
>    CPU at the time when the system was encountering this problem:

It's a buffer leak in the userspace va-api application. The buffers
appear as cached memory, they are not yet accounted against the
applications that have a reference to them. Look at
/sys/kernel/debug/dri/0/i915_gem_objects for a breakdown of users.
-Chris


-- 
Chris Wilson, Intel Open Source Technology Centre