Hi,
sorry for the delay.
On Wed, 29 Jun 2011 20:53:54 -0700, Keith Packard keithp@keithp.com wrote:
On Fri, 24 Jun 2011 17:03:22 +0900, KOSAKI Motohiro kosaki.motohiro@jp.fujitsu.com wrote:
Now, i915_gem_inactive_shrink() should return -1 instead of 0 if it can't take a lock. Otherwise, vmscan is getting a lot of confusing because vmscan can't distinguish "can't take a lock temporary" and "we've shrank all of i915 objects".
This doesn't look like the cleanest change possible. I think it would be better if the shrink function could uniformly return an error indication so that we wouldn't need the weird looking conditional return.
shrink_icache_memory() is good sample code. It doesn't take a lock if sc->nr_to_scan==0. i915_gem_inactive_shrink() should do it too, ideally.
My patch only take a first-aid.
Plus, if I understand correctly, i915_gem_inactive_shrink() have more fundamental issue. actually, shrinker code shouldn't use mutex. Instead, use spinlock. IOW, Don't call kmalloc(GFP_KERNEL) while taking dev->struct_mutex. Otherwise, vmscan in its call path completely fail to shrink i915 cache and it makes big memory reclaim confusing if i915 have a lot of shrinkable pages.
Unless I am mistaken, and there are more patches in flight, the return code from i915_gem_inactive_shrink() is promoted to unsigned long and then used in the calculation of how may objects to evict...
shrinker->shrink has int type value. you can't change i915_gem_inactive_shrink() unless generic shrinker code. Do you really want to change it?