[Intel-xe] [RFC 03/11] drm: introduce drm evictable LRU

[Christian König]

Am 03.11.23 um 05:04 schrieb Zeng, Oak:[SNIP]
> I also want to have a more advanced iterator at some point where we grab
> the BO lock for keeping a reference into the LRU list. Not sure how to
> do this if we don't have the BO here any more.
>
> Need to think about that further,
> Don't quite get the what you want to do with the advanced iterator. But with this work, the lru entity is a base class of ttm_resource or any other resource struct in hmm/svm. Lru is decoupled from bo concept - this is why this lru can be shared with svm code which is bo-less.

This is just a crazy idea I had because TTM tends to perform bad on 
certain tasks.

When we start to evict something we use a callback which indicates if an 
eviction is valuable or not. So it can happen that we have to skip quite 
a bunch of BOs on the LRU until we found one which is worth evicting.

Not it can be that the first eviction doesn't make enough room to 
fulfill the allocation requirement, in this case we currently start over 
at the beginning searching for some BO to evict.

I want to avoid this by being able to have cursors into the LRU, e.g. 
the next BO which can't move until we have evicted the current one.

BTW: How do you handle eviction here? I mean we can't call the evict 
callback with the spinlock held easily?

Christian.

>
> Oak
>
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