On Wed, Mar 23, 2016 at 01:55:14PM +0530, Goel, Akash wrote:
>
>
> On 3/23/2016 1:28 PM, Chris Wilson wrote:
> >On Wed, Mar 23, 2016 at 11:39:44AM +0530, akash.g...@intel.com wrote:
> >>+#ifdef CONFIG_MIGRATION
> >>+static int i915_migratepage(struct address_space *mapping,
> >>+ struct page *newpage, struct page *page,
> >>+ enum migrate_mode mode, void *dev_priv_data)
> >
> >If we move this to i915_gem_shrink_migratepage (i.e. i915_gem_shrink),
> >we can
> >
> >>+ /*
> >>+ * Use trylock here, with a timeout, for struct_mutex as
> >>+ * otherwise there is a possibility of deadlock due to lock
> >>+ * inversion. This path, which tries to migrate a particular
> >>+ * page after locking that page, can race with a path which
> >>+ * truncate/purge pages of the corresponding object (after
> >>+ * acquiring struct_mutex). Since page truncation will also
> >>+ * try to lock the page, a scenario of deadlock can arise.
> >>+ */
> >>+ while (!mutex_trylock(&dev->struct_mutex) && --timeout)
> >>+ schedule_timeout_killable(1);
> >
> >replace this with i915_gem_shrinker_lock() and like constructs with the
> >other shrinkers.
>
> fine, will rename the function to gem_shrink_migratepage, move it
> inside the gem_shrinker.c file, and use the existing constructs.
>
> > Any reason for dropping the early
> > if (!page_private(obj)) skip?
> >
>
> Would this sequence be fine ?
>
> if (!page_private(page))
> goto migrate; /*skip */
>
> Loop for locking mutex
>
> obj = (struct drm_i915_gem_object *)page_private(page);
>
> if (!PageSwapCache(page) && obj) {
Yes.
> >Similarly there are other patterns here that would benefit from
> >integration with existing shrinker logic. However, things like tidying
> >up the pin_display, unbinding, rpm lock inversion are still only on
> >list.
>
> Tidying, like split that one single if condition into multiple if,
> else if blocks ?
Just outstanding patches that simplify the condition and work we have to
do here.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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