[PATCH 0/4] TTM unlockable restartable LRU list iteration

[Christian König]

Am 16.02.24 um 15:20 schrieb Thomas Hellström:
[SNIP]
>> My approach was basically to not only lock the current BO, but also
>> the
>> next one. Since only a locked BO can move on the LRU we effectively
>> created an anchor.
>>
>> Before I dig into the code a couple of questions:
> These are described in the patches but brief comments inline.
>
>> 1. How do you distinct BOs and iteration anchors on the LRU?
> Using a struct ttm_lru_item, containing a struct list_head and the
> type. List nodes embeds this instead of a struct list_head. This is
> larger than the list head but makes it explicit what we're doing.

Need to look deeper into the code of this, but it would be nice if we 
could abstract that better somehow.

>> 2. How do you detect that a bulk list moved on the LRU?
> An age u64 counter on the bulk move that we're comparing against. It's
> updated each time it moves.
>
>
>> 3. How do you remove the iteration anchors from the bulk list?
> A function call at the end of iteration, that the function iterating is
> requried to call.

Thinking quite a bit about that in the last week and I came to the 
conclusion that this might be overkill.

All BOs in a bulk share the same reservation object. So when you 
acquired one you can just keep the dma-resv locked even after evicting 
the BO.

Since moving BOs requires locking the dma-resv object the whole problem 
then just boils down to a list_for_each_element_safe().

That's probably a bit simpler than doing the add/remove dance.

Regards,
Christian.

>
>
> /Thomas
>
>> Regards,
>> Christian.
>>
>>> The restartable property is used in patch 4 to restart swapout if
>>> needed, but the main purpose is this paves the way for
>>> shrinker- and exhaustive eviction.
>>>
>>> Cc: Christian König<christian.koenig at amd.com>
>>> Cc:<dri-devel at lists.freedesktop.org>
>>>
>>> Thomas Hellström (4):
>>>     drm/ttm: Allow TTM LRU list nodes of different types
>>>     drm/ttm: Use LRU hitches
>>>     drm/ttm: Consider hitch moves within bulk sublist moves
>>>     drm/ttm: Allow continued swapout after -ENOSPC falure
>>>
>>>    drivers/gpu/drm/ttm/ttm_bo.c       |   1 +
>>>    drivers/gpu/drm/ttm/ttm_device.c   |  33 +++--
>>>    drivers/gpu/drm/ttm/ttm_resource.c | 202 +++++++++++++++++++++++-
>>> -----
>>>    include/drm/ttm/ttm_resource.h     |  91 +++++++++++--
>>>    4 files changed, 267 insertions(+), 60 deletions(-)
>>>
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