[Intel-gfx] [PATCH v3 0/6] drm/i915: reduce TLB performance regressions
Mauro Carvalho Chehab
mchehab at kernel.org
Wed Jul 27 12:29:50 UTC 2022
Doing TLB invalidation cause performance regressions, like:
[424.370996] i915 0000:00:02.0: [drm] *ERROR* rcs0 TLB invalidation did not complete in 4ms!
As reported at:
https://gitlab.freedesktop.org/drm/intel/-/issues/6424
as this is an expensive operation. So, reduce the need of it by:
- checking if the engine is awake;
- checking if the engine is not wedged;
- batching operations.
Additionally, add a workaround for a known hardware issue on some GPUs.
In order to double-check that this series won't be introducing any regressions,
I used this new IGT test:
https://patchwork.freedesktop.org/patch/495684/?series=106757&rev=1
Checking the results for 3 different patchsets, on Broadwell:
1) On the top of drm-tip (2022y-07m-14d-08h-35m-36) - e. g. with TLB
invalidation and serialization patches:
$ sudo build/tests/gem_exec_tlb|grep Subtest
Subtest close-clear: SUCCESS (10.490s)
Subtest madv-clear: SUCCESS (10.484s)
Subtest u-unmap-clear: SUCCESS (10.527s)
Subtest u-shrink-clear: SUCCESS (10.506s)
Subtest close-dumb: SUCCESS (10.165s)
Subtest madv-dumb: SUCCESS (10.177s)
Subtest u-unmap-dumb: SUCCESS (10.172s)
Subtest u-shrink-dumb: SUCCESS (10.172s)
2) With the new version of the batch TLB invalidation patches from this series:
$ sudo build/tests/gem_exec_tlb|grep Subtest
Subtest close-clear: SUCCESS (10.483s)
Subtest madv-clear: SUCCESS (10.495s)
Subtest u-unmap-clear: SUCCESS (10.545s)
Subtest u-shrink-clear: SUCCESS (10.508s)
Subtest close-dumb: SUCCESS (10.172s)
Subtest madv-dumb: SUCCESS (10.169s)
Subtest u-unmap-dumb: SUCCESS (10.174s)
Subtest u-shrink-dumb: SUCCESS (10.176s)
3) Changing the TLB invalidation routine to do nothing[1]:
$ sudo ~/freedesktop-igt/build/tests/gem_exec_tlb|grep Subtest
(gem_exec_tlb:1958) CRITICAL: Test assertion failure function check_bo, file ../tests/i915/gem_exec_tlb.c:384:
(gem_exec_tlb:1958) CRITICAL: Failed assertion: !sq
(gem_exec_tlb:1958) CRITICAL: Found deadbeef in a new (clear) buffer after 3 tries!
(gem_exec_tlb:1956) CRITICAL: Test assertion failure function check_bo, file ../tests/i915/gem_exec_tlb.c:384:
(gem_exec_tlb:1956) CRITICAL: Failed assertion: !sq
(gem_exec_tlb:1956) CRITICAL: Found deadbeef in a new (clear) buffer after 89 tries!
(gem_exec_tlb:1957) CRITICAL: Test assertion failure function check_bo, file ../tests/i915/gem_exec_tlb.c:384:
(gem_exec_tlb:1957) CRITICAL: Failed assertion: !sq
(gem_exec_tlb:1957) CRITICAL: Found deadbeef in a new (clear) buffer after 256 tries!
(gem_exec_tlb:1960) CRITICAL: Test assertion failure function check_bo, file ../tests/i915/gem_exec_tlb.c:384:
(gem_exec_tlb:1960) CRITICAL: Failed assertion: !sq
(gem_exec_tlb:1960) CRITICAL: Found deadbeef in a new (clear) buffer after 845 tries!
(gem_exec_tlb:1961) CRITICAL: Test assertion failure function check_bo, file ../tests/i915/gem_exec_tlb.c:384:
(gem_exec_tlb:1961) CRITICAL: Failed assertion: !sq
(gem_exec_tlb:1961) CRITICAL: Found deadbeef in a new (clear) buffer after 1138 tries!
(gem_exec_tlb:1954) CRITICAL: Test assertion failure function check_bo, file ../tests/i915/gem_exec_tlb.c:384:
(gem_exec_tlb:1954) CRITICAL: Failed assertion: !sq
(gem_exec_tlb:1954) CRITICAL: Found deadbeef in a new (clear) buffer after 1359 tries!
(gem_exec_tlb:1955) CRITICAL: Test assertion failure function check_bo, file ../tests/i915/gem_exec_tlb.c:384:
(gem_exec_tlb:1955) CRITICAL: Failed assertion: !sq
(gem_exec_tlb:1955) CRITICAL: Found deadbeef in a new (clear) buffer after 1794 tries!
(gem_exec_tlb:1959) CRITICAL: Test assertion failure function check_bo, file ../tests/i915/gem_exec_tlb.c:384:
(gem_exec_tlb:1959) CRITICAL: Failed assertion: !sq
(gem_exec_tlb:1959) CRITICAL: Found deadbeef in a new (clear) buffer after 2139 tries!
Dynamic subtest smem0 failed.
**** DEBUG ****
(gem_exec_tlb:1944) DEBUG: 2M hole:200000 contains poison:6b6b6b6b
(gem_exec_tlb:1944) DEBUG: Running writer for 200000 at 300000 on bcs0
(gem_exec_tlb:1944) DEBUG: Closing hole:200000 on rcs0, sample:deadbeef
(gem_exec_tlb:1944) DEBUG: Rechecking hole:200000, sample:6b6b6b6b
**** END ****
Subtest close-clear: FAIL (10.434s)
Subtest madv-clear: SUCCESS (10.479s)
Subtest u-unmap-clear: SUCCESS (10.512s)
In summary, the test does properly detect fail when TLB cache invalidation doesn't happen,
as shown at result (3). It also shows that both current drm-tip and drm-tip with this series
applied don't have TLB invalidation cache issues.
[1] I applied this patch on the top of drm-tip:
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 68c2b0d8f187..0aefcd7be5e9 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -930,0 +931,3 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
+ // HACK: don't do TLB invalidations!!!
+ return;
+
Regards,
Mauro
Chris Wilson (4):
drm/i915/gt: Ignore TLB invalidations on idle engines
drm/i915/gt: Invalidate TLB of the OA unit at TLB invalidations
drm/i915/gt: Skip TLB invalidations once wedged
drm/i915/gt: Batch TLB invalidations
Mauro Carvalho Chehab (2):
drm/i915/gt: document with_intel_gt_pm_if_awake()
drm/i915/gt: describe the new tlb parameter at i915_vma_resource
.../gpu/drm/i915/gem/i915_gem_object_types.h | 3 +-
drivers/gpu/drm/i915/gem/i915_gem_pages.c | 25 +++---
drivers/gpu/drm/i915/gt/intel_gt.c | 77 +++++++++++++++----
drivers/gpu/drm/i915/gt/intel_gt.h | 12 ++-
drivers/gpu/drm/i915/gt/intel_gt_pm.h | 11 +++
drivers/gpu/drm/i915/gt/intel_gt_types.h | 18 ++++-
drivers/gpu/drm/i915/gt/intel_ppgtt.c | 8 +-
drivers/gpu/drm/i915/i915_vma.c | 33 ++++++--
drivers/gpu/drm/i915/i915_vma.h | 1 +
drivers/gpu/drm/i915/i915_vma_resource.c | 9 ++-
drivers/gpu/drm/i915/i915_vma_resource.h | 6 +-
11 files changed, 163 insertions(+), 40 deletions(-)
--
2.36.1
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