| Message ID | 20240722074540.15295-1-david@davidgow.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915: Allow evicting to use the requested placement | expand |
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c index e6f177183c0f..fb848fd8ba15 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c @@ -165,7 +165,6 @@ i915_ttm_placement_from_obj(const struct drm_i915_gem_object *obj, i915_ttm_place_from_region(num_allowed ? obj->mm.placements[0] : obj->mm.region, &places[0], obj->bo_offset, obj->base.size, flags); - places[0].flags |= TTM_PL_FLAG_DESIRED; /* Cache this on object? */ for (i = 0; i < num_allowed; ++i) {
In a78a8da5 ("drm/ttm: replace busy placement with flags v6"), the old system of having a separate placement list (for placements which should be used without eviction) and a 'busy' placement list (for placements which should be attempted if eviction is required) was replaced with a new one where placements could be marked 'FALLBACK' (to be attempted if eviction is required) or 'DESIRED' (to be attempted first, but not if eviction is required). i915 had always included the requested placement in the list of 'busy' placements: i.e., the placement could be used either if eviction is required or not. But when the new system was put in place, the requested (first) placement was marked 'DESIRED', so would never be used if eviction became necessary. While a bug in the original commit prevented this flag from working, when this was fixed in 4a0e7b3c ("drm/i915: fix applying placement flag"), it caused long hangs on DG2 systems with small BAR. Don't mark the requested placement DESIRED (or FALLBACK), allowing it to be used in both situations. This matches the old behaviour, and resolves the hangs. Thanks to Justin Brewer for bisecting the issue. Fixes: a78a8da51b36 ("drm/ttm: replace busy placement with flags v6") Fixes: 4a0e7b3c3753 ("drm/i915: fix applying placement flag") Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11255 Signed-off-by: David Gow <david@davidgow.net> --- I'm not 100% sure I understand exactly what went wrong here: I'm pretty sure the patch is correct, but let me know if the commit description is way off base. My system works much better with this applied, but it's possible that it could work better still with further changes: the buddy allocator is still chewing up a lot of the CPU, and there are still cases where this notably affects performance (though, in my experience, these are now 'hitches' rather than multi-minute hangs). Cheers, -- David --- drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 1 - 1 file changed, 1 deletion(-)