From: Tvrtko Ursulin tvrtko.ursulin@intel.com
Usage of Transparent Hugepages was disabled in 9987da4b5dcf ("drm/i915: Disable THP until we have a GPU read BW W/A"), but since it appears majority of performance regressions reported with an enabled IOMMU can be almost eliminated by turning them on, lets do that by adding a couple of Kconfig options.
To err on the side of safety we keep the current default in cases where IOMMU is not active, and only when it is default to the "huge=within_size" mode. Although there probably would be wins to enable them throughout, more extensive testing across benchmarks and platforms would need to be done.
With the patch and IOMMU enabled my local testing on a small Skylake part shows OglVSTangent regression being reduced from ~14% to ~2%.
References: b901bb89324a ("drm/i915/gemfs: enable THP") References: 9987da4b5dcf ("drm/i915: Disable THP until we have a GPU read BW W/A") References: https://gitlab.freedesktop.org/drm/intel/-/issues/430 Co-developed-by: Chris Wilson chris@chris-wilson.co.uk Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Joonas Lahtinen joonas.lahtinen@linux.intel.com Cc: Matthew Auld matthew.auld@intel.com Cc: Eero Tamminen eero.t.tamminen@intel.com Cc: Tvrtko Ursulin tvrtko.ursulin@intel.com Signed-off-by: Tvrtko Ursulin tvrtko.ursulin@intel.com --- drivers/gpu/drm/i915/Kconfig.profile | 46 +++++++++++++++++++++++++++ drivers/gpu/drm/i915/gem/i915_gemfs.c | 11 +++++-- 2 files changed, 55 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile index 39328567c200..c64c3d39a0f9 100644 --- a/drivers/gpu/drm/i915/Kconfig.profile +++ b/drivers/gpu/drm/i915/Kconfig.profile @@ -119,3 +119,49 @@ config DRM_I915_TIMESLICE_DURATION /sys/class/drm/card?/engine/*/timeslice_duration_ms
May be 0 to disable timeslicing. + +choice + prompt "Transparent Hugepage Support (native)" + default DRM_I915_THP_NATIVE_NEVER + help + Select the preferred method for allocating from Transparent Hugepages + when IOMMU is not enabled. + + config DRM_I915_THP_NATIVE_NEVER + bool "Never" + + config DRM_I915_THP_NATIVE_WITHIN + bool "Within" + + config DRM_I915_THP_NATIVE_ALWAYS + bool "Always" +endchoice + +config DRM_I915_THP_NATIVE + string + default "always" if DRM_I915_THP_NATIVE_ALWAYS + default "within_size" if DRM_I915_THP_NATIVE_WITHIN + default "never" if DRM_I915_THP_NATIVE_NEVER + +choice + prompt "Transparent Hugepage Support (IOMMU)" + default DRM_I915_THP_IOMMU_WITHIN + help + Select the preferred method for allocating from Transparent Hugepages + with IOMMU active. + + config DRM_I915_THP_IOMMU_NEVER + bool "Never" + + config DRM_I915_THP_IOMMU_WITHIN + bool "Within" + + config DRM_I915_THP_IOMMU_ALWAYS + bool "Always" +endchoice + +config DRM_I915_THP_IOMMU + string + default "always" if DRM_I915_THP_IOMMU_ALWAYS + default "within_size" if DRM_I915_THP_IOMMU_WITHIN + default "never" if DRM_I915_THP_IOMMU_NEVER diff --git a/drivers/gpu/drm/i915/gem/i915_gemfs.c b/drivers/gpu/drm/i915/gem/i915_gemfs.c index 5e6e8c91ab38..b71d2b2d2ada 100644 --- a/drivers/gpu/drm/i915/gem/i915_gemfs.c +++ b/drivers/gpu/drm/i915/gem/i915_gemfs.c @@ -13,8 +13,11 @@
int i915_gemfs_init(struct drm_i915_private *i915) { + char thp_native[] = "huge=" CONFIG_DRM_I915_THP_NATIVE; + char thp_iommu[] = "huge=" CONFIG_DRM_I915_THP_IOMMU; struct file_system_type *type; struct vfsmount *gemfs; + char *opts;
type = get_fs_type("tmpfs"); if (!type) @@ -26,15 +29,19 @@ int i915_gemfs_init(struct drm_i915_private *i915) * * One example, although it is probably better with a per-file * control, is selecting huge page allocations ("huge=within_size"). - * Currently unused due to bandwidth issues (slow reads) on Broadwell+. + * However, we only do so to offset the overhead of iommu lookups + * due to bandwidth issues (slow reads) on Broadwell+. */ + opts = intel_vtd_active() ? thp_iommu : thp_native;
- gemfs = kern_mount(type); + gemfs = vfs_kern_mount(type, SB_KERNMOUNT, type->name, opts); if (IS_ERR(gemfs)) return PTR_ERR(gemfs);
i915->mm.gemfs = gemfs;
+ drm_info(&i915->drm, "Transparent Hugepage mode '%s'", opts); + return 0; }