On 7/28/20 4:42 PM, Chris Wilson wrote:
Quoting Thomas Hellström (Intel) (2020-07-23 15:33:20)
On 2020-07-15 13:50, Chris Wilson wrote:
We need to make the DMA allocations used for page directories to be
performed up front so that we can include those allocations in our
memory reservation pass. The downside is that we have to assume the
worst case, even before we know the final layout, and always allocate
enough page directories for this object, even when there will be overlap.
This unfortunately can be quite expensive, especially as we have to
clear/reset the page directories and DMA pages, but it should only be
required during early phases of a workload when new objects are being
discovered, or after memory/eviction pressure when we need to rebind.
Once we reach steady state, the objects should not be moved and we no
longer need to preallocating the pages tables.
It should be noted that the lifetime for the page directories DMA is
more or less decoupled from individual fences as they will be shared
across objects across timelines.
v2: Only allocate enough PD space for the PTE we may use, we do not need
to allocate PD that will be left as scratch.
v3: Store the shift unto the first PD level to encapsulate the different
PTE counts for gen6/gen8.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
---
.../gpu/drm/i915/gem/i915_gem_client_blt.c | 11 +--
drivers/gpu/drm/i915/gt/gen6_ppgtt.c | 40 ++++-----
drivers/gpu/drm/i915/gt/gen8_ppgtt.c | 78 +++++------------
drivers/gpu/drm/i915/gt/intel_ggtt.c | 60 ++++++--------
drivers/gpu/drm/i915/gt/intel_gtt.h | 46 ++++++----
drivers/gpu/drm/i915/gt/intel_ppgtt.c | 83 ++++++++++++++++---
drivers/gpu/drm/i915/i915_vma.c | 27 +++---
drivers/gpu/drm/i915/selftests/i915_gem_gtt.c | 60 ++++++++------
drivers/gpu/drm/i915/selftests/mock_gtt.c | 22 ++---
9 files changed, 237 insertions(+), 190 deletions(-)
Hi, Chris,
Overall looks good, but a question: Why can't we perform page-table
memory allocation on demand when needed?
We need to allocate device memory for the page tables. The intention
here is gather up all the resource requirements for an operation and
reserve them in a single pass.
Are we then under a mutex that we also take during reclaim?
Yes, the vm->mutex is used during the shrinker to revoke the GPU
bindings before returning memory to the system.
-Chris
Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxx>
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