[PATCH v2 0/9] TTM shrinker helpers and xe buffer object shrinker

Tue Apr 16 13:24:45 UTC 2024

Am 16.04.24 um 15:08 schrieb Thomas Hellström:
> Hi, Christian,
>
> On Tue, 2024-04-16 at 13:55 +0200, Christian König wrote:
>> While patches 1-4 look good from a high level I still think it needs
>> some prerequisite and re-ordering.
>>
>> First of all make all the cleanups separate patches. In other words
>> that
>> ttm_resource_manager_next() takes only the cursor as argument, adding
>> ttm_resource_cursor_fini()/ttm_resource_cursor_fini_locked() as one
>> patch and then ttm_lru_bulk_move_init()/ttm_lru_bulk_move_fini() as
>> second.
> Yes, I can take a look at that. I think the shortening of the argument
> list of ttm_resource_manager_next() makes sense as a separate cleanup.
>
> The other two are needed because of the changes introduced in the
> respective patches. I could of course add stubs of these functions
> before the patch that currently introduce them if needed, but don't
> really see the point. What do you think.

Na, stubs doesn't make sense.

I was under the expression that you would have something to do for them 
even without the LRU patch. If that's not the case then just skip that.

>
>> With that done I think we should first switch over TTM and all
>> drivers
>> using it to drm_exec as part of it's context object.
> So are you ok with adding an optional drm_exec pointer in the
> ttm_operation_ctx for this? (That was my plan moving forward).

Yeah, perfectly valid. My thinking was just to do that first.

>
> However, when that has been added, I think it makes sense to leave to
> the driver author to port their validation loops and bo allocation over
> to using drm_exec. While we made sure the drm_exec object was indeed
> passed to the validation helper in the drm_gpuvm code, I'm not sure
> everybody actually includes their validation and bo allocation (for
> example page-table-bos) in their drm_exec while_not_all_locked() loop,
> and I think it's reasonable to require the "port the driver over" to be
> an optional but strongly recommended driver effort. If the driver sets
> ctx->drm_exec to NULL, it will fallback to current behaviour.

For the intermediate case I think it makes sense to have this optional, 
but in the long run we should make it mandatory.

>
>> Then I would switch over to using LRU hitches for both swapping and
>> eviction.
>>
>> And when that's finally done we can take a look into the partial
>> shmem
>> swapping :)
>>
>> And Felix is really (and mean *really*) looking forward to the
>> partial
>> shmem swapping as well.
> While the LRU walker helper introduced in patch 8 has drm_exec support,
> shrinkers don't require it, since they are always trylocking. (However
> being able to "evict" system to swap directly in the validation stage
> using drm_exec locking is probably something we should support).
>
> That's why I opted for implementing shrinking before exhaustive
> eviction. But if you insist we can do it the other way around. Most of
> what's needed is already in the patches.

I don't care about the order in which things are implemented, but I 
think we should have at least some eviction prototype as well for testing.

Eviction is just the much easier to exercise use case.

Regards,
Christian.

>
> /Thomas
>
>
>> Regards,
>> Christian.
>>
>> Am 16.04.24 um 12:07 schrieb Thomas Hellström:
>>> This series implements TTM shrinker / eviction helpers and an xe bo
>>> shrinker. It builds on two previous series, *and obsoletes these*.
>>> First
>>>
>>> https://www.mail-archive.com/dri-devel@lists.freedesktop.org/msg484425.html
>>>
>>> for patch 1-4, which IMO still could be reviewed and pushed as a
>>> separate series.
>>>
>>> Second the previous TTM shrinker series
>>>
>>> https://lore.kernel.org/linux-mm/b7491378-defd-4f1c-31e2-29e4c77e2d67@amd.com/T/
>>>
>>> Where the comment about layering
>>> https://lore.kernel.org/linux-mm/b7491378-defd-4f1c-31e2-29e4c77e2d67@amd.com/T/#ma918844aa8a6efe8768fdcda0c6590d5c93850c9
>>>
>>> now addressed, and this version also implements shmem objects for
>>> backup
>>> rather than direct swap-cache insertions, which was used in the
>>> previuos
>>> series. It turns out that with per-page backup / shrinking, shmem
>>> objects
>>> appears to work just as well as direct swap-cache insertions with
>>> the
>>> added benefit that was introduced in the previous TTM shrinker
>>> series to
>>> avoid running out of swap entries isn't really needed.
>>>
>>> In any case, patch 1-4 are better described in their separate
>>> series.
>>> (RFC is removed for those).
>>>
>>> Patch 5 could in theory be skipped but introduces a possibility to
>>> easily
>>> add or test multiple backup backends, like the direct swap-cache
>>> insertion or even files into fast dedicated nvme storage for for
>>> example.
>>>
>>> Patch 6 introduces helpers in the ttm_pool code for page-by-page
>>> shrinking
>>> and recovery. It avoids having to temporarily allocate a huge
>>> amount of
>>> memory to be able to shrink a buffer object. It also introduces the
>>> possibility to immediately write-back pages if needed, since that
>>> tends
>>> to be a bit delayed when left to kswapd.
>>>
>>> Patch 7 Adds a simple error injection to the above code to help
>>> increase
>>> test coverage.
>>>
>>> Patch 8 introduces a LRU walk helper for eviction and shrinking.
>>> It's
>>> currently xe-only but not xe-specific and can easily be moved to
>>> TTM when
>>> used by more than one driver or when eviction is implemented using
>>> it.
>>>
>>> Patch 9 introduces a helper callback for shrinking (Also ready to
>>> be
>>> moved to TTM) and an xe-specific shrinker implementation. It also
>>> adds a kunit test to test the shrinker functionality by trying to
>>> allocate twice the available amount of RAM as buffer objects. If
>>> there
>>> is no swap-space available, the buffer objects are marked
>>> purgeable.
>>>
>>> v2:
>>> - Squash obsolete revision history in the patch commit messages.
>>> - Fix a couple of review comments by Christian
>>> - Don't store the mem_type in the TTM managers but in the
>>>     resource cursor.
>>> - Rename introduced TTM *back_up* function names to *backup*
>>> - Add ttm pool recovery fault injection.
>>> - Shrinker xe kunit test
>>> - Various bugfixes
>>>
>>> Cc: Somalapuram Amaranath <Amaranath.Somalapuram at amd.com>
>>> Cc: Christian König <christian.koenig at amd.com>
>>> Cc: <dri-devel at lists.freedesktop.org>
>>>
>>> Thomas Hellström (8):
>>>     drm/ttm: Allow TTM LRU list nodes of different types
>>>     drm/ttm: Use LRU hitches
>>>     drm/ttm, drm/amdgpu, drm/xe: Consider hitch moves within bulk
>>> sublist
>>>       moves
>>>     drm/ttm: Allow continued swapout after -ENOSPC falure
>>>     drm/ttm: Add a virtual base class for graphics memory backup
>>>     drm/ttm/pool: Provide a helper to shrink pages.
>>>     drm/xe, drm/ttm: Provide a generic LRU walker helper
>>>     drm/xe: Add a shrinker for xe bos
>>>
>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c |   4 +
>>>    drivers/gpu/drm/ttm/Makefile           |   2 +-
>>>    drivers/gpu/drm/ttm/ttm_backup_shmem.c | 137 +++++++++
>>>    drivers/gpu/drm/ttm/ttm_bo.c           |   1 +
>>>    drivers/gpu/drm/ttm/ttm_device.c       |  33 ++-
>>>    drivers/gpu/drm/ttm/ttm_pool.c         | 391
>>> ++++++++++++++++++++++++-
>>>    drivers/gpu/drm/ttm/ttm_resource.c     | 231 ++++++++++++---
>>>    drivers/gpu/drm/ttm/ttm_tt.c           |  34 +++
>>>    drivers/gpu/drm/xe/Makefile            |   2 +
>>>    drivers/gpu/drm/xe/xe_bo.c             | 123 ++++++--
>>>    drivers/gpu/drm/xe/xe_bo.h             |   3 +
>>>    drivers/gpu/drm/xe/xe_device.c         |   8 +
>>>    drivers/gpu/drm/xe/xe_device_types.h   |   2 +
>>>    drivers/gpu/drm/xe/xe_shrinker.c       | 237 +++++++++++++++
>>>    drivers/gpu/drm/xe/xe_shrinker.h       |  18 ++
>>>    drivers/gpu/drm/xe/xe_ttm_helpers.c    | 224 ++++++++++++++
>>>    drivers/gpu/drm/xe/xe_ttm_helpers.h    |  63 ++++
>>>    drivers/gpu/drm/xe/xe_vm.c             |   4 +
>>>    include/drm/ttm/ttm_backup.h           | 136 +++++++++
>>>    include/drm/ttm/ttm_device.h           |   2 +
>>>    include/drm/ttm/ttm_pool.h             |   4 +
>>>    include/drm/ttm/ttm_resource.h         |  96 +++++-
>>>    include/drm/ttm/ttm_tt.h               |  19 ++
>>>    23 files changed, 1683 insertions(+), 91 deletions(-)
>>>    create mode 100644 drivers/gpu/drm/ttm/ttm_backup_shmem.c
>>>    create mode 100644 drivers/gpu/drm/xe/xe_shrinker.c
>>>    create mode 100644 drivers/gpu/drm/xe/xe_shrinker.h
>>>    create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.c
>>>    create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.h
>>>    create mode 100644 include/drm/ttm/ttm_backup.h
>>>