On (21/06/17 19:27), Daniel Vetter wrote:
So can all allocations in gen8_init_scratch() use GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN
Yeah that looks all fairly broken tbh. The only thing I didn't know was that GFP_DMA32 wasn't a full gfp mask with reclaim bits set as needed. I guess it would be clearer if we use GFP_KERNEL | __GFP_DMA32 for these.
Looks good.
The commit that introduced a lot of this, including I915_GFP_ALLOW_FAIL seems to be
commit 1abb70f5955d1a9021f96359a2c6502ca569b68d Author: Chris Wilson chris@chris-wilson.co.uk Date: Tue May 22 09:36:43 2018 +0100
drm/i915/gtt: Allow pagedirectory allocations to failwhich used a selftest as justification, not real world workloads, so looks rather dubious.
Exactly, the commit we landed internally partially reverts 1abb70f5955 in 4.19 and 5.4 kernels. I don't mind I915_GFP_ALLOW_FAIL and so on, I kept those bits, but we need reclaim. I can reproduce cases when order:0 allocation fails with __GFP_HIGHMEM|__GFP_RETRY_MAYFAIL but succeeds with GFP_KERNEL|__GFP_HIGHMEM|__GFP_RETRY_MAYFAIL
ON a side note, I'm not very sure if __GFP_RETRY_MAYFAIL is actually needed. Especially seeing it in syscalls is a bit uncommon:
drm_ioctl() i915_gem_context_create_ioctl() i915_gem_create_context() i915_ppgtt_create() setup_scratch_page() // __GFP_RETRY_MAYFAIL
But with GFP_KERNEL at least it tries to make some reclaim progress between retries, so it seems to be good enough.