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

Message ID 20240416100730.6666-1-thomas.hellstrom@linux.intel.com (mailing list archive)
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Series TTM shrinker helpers and xe buffer object shrinker | expand

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Thomas Hellstrom April 16, 2024, 10:07 a.m. UTC
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@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: <dri-devel@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

Comments

Christian König April 16, 2024, 11:55 a.m. UTC | #1
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.

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.

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.

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@amd.com>
> Cc: Christian König <christian.koenig@amd.com>
> Cc: <dri-devel@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
>
Thomas Hellstrom April 16, 2024, 1:08 p.m. UTC | #2
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.

> 
> 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).

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.

> 
> 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.

/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@amd.com>
> > Cc: Christian König <christian.koenig@amd.com>
> > Cc: <dri-devel@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
> > 
>
Christian König April 16, 2024, 1:24 p.m. UTC | #3
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@amd.com>
>>> Cc: Christian König <christian.koenig@amd.com>
>>> Cc: <dri-devel@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
>>>