Re: [PATCH v8 20/34] i915: bail out earlier when shrinker cannot acquire mutex

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, May 24, 2013 at 03:59:14PM +0530, Glauber Costa wrote:
> The main shrinker driver will keep trying for a while to free objects if
> the returned value from the shrink scan procedure is 0.  That means "no
> objects now", but a retry could very well succeed.
> 
> A negative value has a different meaning. It means it is impossible to
> shrink, and we would better bail out soon. We find this behavior more
> appropriate for the case where the lock cannot be taken. Specially given
> the hammer behavior of the i915: if another thread is already shrinking,
> we are likely not to be able to shrink anything anyway when we finally
> acquire the mutex.
> 
> Signed-off-by: Glauber Costa <glommer@openvz.org>
> CC: Dave Chinner <dchinner@redhat.com>
> CC: Mel Gorman <mgorman@suse.de>
> CC: Daniel Vetter <daniel.vetter@ffwll.ch>
> CC: Kent Overstreet <koverstreet@google.com>

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/i915/i915_gem.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 6b17122..52b3ac1 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -4448,10 +4448,10 @@ i915_gem_inactive_count(struct shrinker *shrinker, struct shrink_control *sc)
>  
>  	if (!mutex_trylock(&dev->struct_mutex)) {
>  		if (!mutex_is_locked_by(&dev->struct_mutex, current))
> -			return 0;
> +			return -1;
>  
>  		if (dev_priv->mm.shrinker_no_lock_stealing)
> -			return 0;
> +			return -1;
>  
>  		unlock = false;
>  	}
> -- 
> 1.8.1.4
> 

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

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