Re: [Intel-gfx] [PATCH v6 7/9] drm/i915: Reduce the number of objects subject to memcpy recover

Thomas Hellström
2021-09-23T09:58:45Z

On 9/23/21 11:44 AM, Matthew Auld wrote:
> On 22/09/2021 07:25, Thomas Hellström wrote:
>> We really only need memcpy restore for objects that affect the
>> operability of the migrate context. That is, primarily the page-table
>> objects of the migrate VM.
>>
>> Add an object flag, I915_BO_ALLOC_PM_EARLY for objects that need early
>> restores using memcpy and a way to assign LMEM page-table object flags
>> to be used by the vms.
>>
>> Restore objects without this flag with the gpu blitter and only objects
>> carrying the flag using TTM memcpy.
>>
>> Initially mark the migrate, gt, gtt and vgpu vms to use this flag, and
>> defer for a later audit which vms actually need it. Most importantly,
>> user-
>> allocated vms with pinned page-table objects can be restored using the
>> blitter.
>>
>> Performance-wise memcpy restore is probably as fast as gpu restore if
>> not
>> faster, but using gpu restore will help tackling future restrictions in
>> mappable LMEM size.
>>
>> v4:
>> - Don't mark the aliasing ppgtt page table flags for early resume, but
>>    rather the ggtt page table flags as intended. (Matthew Auld)
>> - The check for user buffer objects during early resume is pointless,
>> since
>>    they are never marked I915_BO_ALLOC_PM_EARLY. (Matthew Auld)
>> v5:
>> - Mark GuC LMEM objects with I915_BO_ALLOC_PM_EARLY to have them
>> restored
>>    before we fire up the migrate context.
>>
>> Cc: Matthew Brost <matthew.brost@intel.com>
>> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>> Reviewed-by: Matthew Auld <matthew.auld@intel.com>
>> ---
>>   drivers/gpu/drm/i915/gem/i915_gem_context.c      |  4 ++--
>>   drivers/gpu/drm/i915/gem/i915_gem_object_types.h |  9 ++++++---
>>   drivers/gpu/drm/i915/gem/i915_gem_pm.c           |  6 +++++-
>>   drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c       |  5 +++--
>>   drivers/gpu/drm/i915/gem/selftests/huge_pages.c  |  2 +-
>>   drivers/gpu/drm/i915/gt/gen6_ppgtt.c             |  2 +-
>>   drivers/gpu/drm/i915/gt/gen8_ppgtt.c             |  5 +++--
>>   drivers/gpu/drm/i915/gt/gen8_ppgtt.h             |  4 +++-
>>   drivers/gpu/drm/i915/gt/intel_ggtt.c             |  3 ++-
>>   drivers/gpu/drm/i915/gt/intel_gt.c               |  2 +-
>>   drivers/gpu/drm/i915/gt/intel_gtt.c              |  3 ++-
>>   drivers/gpu/drm/i915/gt/intel_gtt.h              |  9 +++++++--
>>   drivers/gpu/drm/i915/gt/intel_migrate.c          |  2 +-
>>   drivers/gpu/drm/i915/gt/intel_ppgtt.c            | 13 ++++++++-----
>>   drivers/gpu/drm/i915/gt/selftest_hangcheck.c     |  2 +-
>>   drivers/gpu/drm/i915/gt/uc/intel_guc.c           |  3 ++-
>>   drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c         |  7 +++++--
>>   drivers/gpu/drm/i915/gvt/scheduler.c             |  2 +-
>>   drivers/gpu/drm/i915/selftests/i915_gem_gtt.c    |  4 ++--
>>   19 files changed, 56 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c
>> b/drivers/gpu/drm/i915/gem/i915_gem_context.c
>> index c2ab0e22db0a..8208fd5b72c3 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
>> @@ -1287,7 +1287,7 @@ i915_gem_create_context(struct drm_i915_private
>> *i915,
>>       } else if (HAS_FULL_PPGTT(i915)) {
>>           struct i915_ppgtt *ppgtt;
>>   -        ppgtt = i915_ppgtt_create(&i915->gt);
>> +        ppgtt = i915_ppgtt_create(&i915->gt, 0);
>>           if (IS_ERR(ppgtt)) {
>>               drm_dbg(&i915->drm, "PPGTT setup failed (%ld)\n",
>>                   PTR_ERR(ppgtt));
>> @@ -1465,7 +1465,7 @@ int i915_gem_vm_create_ioctl(struct drm_device
>> *dev, void *data,
>>       if (args->flags)
>>           return -EINVAL;
>>   -    ppgtt = i915_ppgtt_create(&i915->gt);
>> +    ppgtt = i915_ppgtt_create(&i915->gt, 0);
>>       if (IS_ERR(ppgtt))
>>           return PTR_ERR(ppgtt);
>>   diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>> b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>> index 118691ce81d7..fa2ba9e2a4d0 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>> @@ -294,13 +294,16 @@ struct drm_i915_gem_object {
>>   #define I915_BO_ALLOC_USER        BIT(3)
>>   /* Object is allowed to lose its contents on suspend / resume, even
>> if pinned */
>>   #define I915_BO_ALLOC_PM_VOLATILE BIT(4)
>> +/* Object needs to be restored early using memcpy during resume */
>> +#define I915_BO_ALLOC_PM_EARLY    BIT(5)
>>   #define I915_BO_ALLOC_FLAGS (I915_BO_ALLOC_CONTIGUOUS | \
>>                    I915_BO_ALLOC_VOLATILE | \
>>                    I915_BO_ALLOC_CPU_CLEAR | \
>>                    I915_BO_ALLOC_USER | \
>> -                 I915_BO_ALLOC_PM_VOLATILE)
>> -#define I915_BO_READONLY          BIT(5)
>> -#define I915_TILING_QUIRK_BIT     6 /* unknown swizzling; do not
>> release! */
>> +                 I915_BO_ALLOC_PM_VOLATILE | \
>> +                 I915_BO_ALLOC_PM_EARLY)
>> +#define I915_BO_READONLY          BIT(6)
>> +#define I915_TILING_QUIRK_BIT     7 /* unknown swizzling; do not
>> release! */
>>         /**
>>        * @mem_flags - Mutable placement-related flags
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pm.c
>> b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
>> index 12b37b4c1192..726b40e1fbb0 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_pm.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
>> @@ -97,8 +97,12 @@ int i915_gem_backup_suspend(struct
>> drm_i915_private *i915)
>>        * More objects may have become unpinned as requests were
>>        * retired. Now try to evict again. The gt may be wedged here
>>        * in which case we automatically fall back to memcpy.
>> +     * We allow also backing up pinned objects that have not been
>> +     * marked for early recover, and that may contain, for example,
>> +     * page-tables for the migrate context.
>>        */
>> -    ret = lmem_suspend(i915, I915_TTM_BACKUP_ALLOW_GPU);
>> +    ret = lmem_suspend(i915, I915_TTM_BACKUP_ALLOW_GPU |
>> +               I915_TTM_BACKUP_PINNED);
>>       if (ret)
>>           goto out_recover;
>>   diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
>> b/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
>> index 03a00d193f40..3b6d14b5c604 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
>> @@ -57,7 +57,8 @@ static int i915_ttm_backup(struct
>> i915_gem_apply_to_region *apply,
>>       if (pm_apply->allow_gpu && i915_gem_object_evictable(obj))
>>           return ttm_bo_validate(bo, i915_ttm_sys_placement(), &ctx);
>>   -    if (!pm_apply->backup_pinned)
>> +    if (!pm_apply->backup_pinned ||
>> +        (pm_apply->allow_gpu && (obj->flags & I915_BO_ALLOC_PM_EARLY)))
>>           return 0;
>>         if (obj->flags & I915_BO_ALLOC_PM_VOLATILE)
>> @@ -155,7 +156,7 @@ static int i915_ttm_restore(struct
>> i915_gem_apply_to_region *apply,
>>       if (!backup)
>>           return 0;
>>   -    if (!pm_apply->allow_gpu && (obj->flags & I915_BO_ALLOC_USER))
>> +    if (!pm_apply->allow_gpu && !(obj->flags & I915_BO_ALLOC_PM_EARLY))
>>           return 0;
>>         err = i915_gem_object_lock(backup, apply->ww);
>> diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
>> b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
>> index 0827634c842c..77d84a9e8789 100644
>> --- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
>> +++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
>> @@ -1645,7 +1645,7 @@ int i915_gem_huge_page_mock_selftests(void)
>>       mkwrite_device_info(dev_priv)->ppgtt_type = INTEL_PPGTT_FULL;
>>       mkwrite_device_info(dev_priv)->ppgtt_size = 48;
>>   -    ppgtt = i915_ppgtt_create(&dev_priv->gt);
>> +    ppgtt = i915_ppgtt_create(&dev_priv->gt, 0);
>>       if (IS_ERR(ppgtt)) {
>>           err = PTR_ERR(ppgtt);
>>           goto out_unlock;
>> diff --git a/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
>> b/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
>> index 1aee5e6b1b23..890191f286e3 100644
>> --- a/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
>> +++ b/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
>> @@ -429,7 +429,7 @@ struct i915_ppgtt *gen6_ppgtt_create(struct
>> intel_gt *gt)
>>       mutex_init(&ppgtt->flush);
>>       mutex_init(&ppgtt->pin_mutex);
>>   -    ppgtt_init(&ppgtt->base, gt);
>> +    ppgtt_init(&ppgtt->base, gt, 0);
>>       ppgtt->base.vm.pd_shift = ilog2(SZ_4K * SZ_4K /
>> sizeof(gen6_pte_t));
>>       ppgtt->base.vm.top = 1;
>>   diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
>> b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
>> index 6a5af995f5b1..037a9a6e4889 100644
>> --- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
>> +++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
>> @@ -753,7 +753,8 @@ gen8_alloc_top_pd(struct i915_address_space *vm)
>>    * space.
>>    *
>>    */
>> -struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt)
>> +struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt,
>> +                     unsigned long lmem_pt_obj_flags)
>>   {
>>       struct i915_ppgtt *ppgtt;
>>       int err;
>> @@ -762,7 +763,7 @@ struct i915_ppgtt *gen8_ppgtt_create(struct
>> intel_gt *gt)
>>       if (!ppgtt)
>>           return ERR_PTR(-ENOMEM);
>>   -    ppgtt_init(ppgtt, gt);
>> +    ppgtt_init(ppgtt, gt, lmem_pt_obj_flags);
>>       ppgtt->vm.top = i915_vm_is_4lvl(&ppgtt->vm) ? 3 : 2;
>>       ppgtt->vm.pd_shift = ilog2(SZ_4K * SZ_4K / sizeof(gen8_pte_t));
>>   diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.h
>> b/drivers/gpu/drm/i915/gt/gen8_ppgtt.h
>> index b9028c2ad3c7..f541d19264b4 100644
>> --- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.h
>> +++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.h
>> @@ -12,7 +12,9 @@ struct i915_address_space;
>>   struct intel_gt;
>>   enum i915_cache_level;
>>   -struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt);
>> +struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt,
>> +                     unsigned long lmem_pt_obj_flags);
>> +
>>   u64 gen8_ggtt_pte_encode(dma_addr_t addr,
>>                enum i915_cache_level level,
>>                u32 flags);
>> diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c
>> b/drivers/gpu/drm/i915/gt/intel_ggtt.c
>> index 8d71f67926f1..06576fc1310e 100644
>> --- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
>> +++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
>> @@ -644,7 +644,7 @@ static int init_aliasing_ppgtt(struct i915_ggtt
>> *ggtt)
>>       struct i915_ppgtt *ppgtt;
>>       int err;
>>   -    ppgtt = i915_ppgtt_create(ggtt->vm.gt);
>> +    ppgtt = i915_ppgtt_create(ggtt->vm.gt, 0);
>>       if (IS_ERR(ppgtt))
>>           return PTR_ERR(ppgtt);
>>   @@ -909,6 +909,7 @@ static int gen8_gmch_probe(struct i915_ggtt *ggtt)
>>           size = gen8_get_total_gtt_size(snb_gmch_ctl);
>>         ggtt->vm.alloc_pt_dma = alloc_pt_dma;
>> +    ggtt->vm.lmem_pt_obj_flags = I915_BO_ALLOC_PM_EARLY;
>
> The scratch page is still in system memory for the ggtt, so I guess
> this is not needed? Although maybe that will change, so probably good
> to keep?

Hmm, yes, I guess lets keep this for a possible future audit for now. I
think there are other vms that may not need this flag either.

Thanks for  reviewing!

/Thomas