From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx <Intel-gfx@lists.freedesktop.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
Tvrtko Ursulin <tvrtko.ursulin@intel.com>,
Chris Wilson <chris@chris-wilson.co.uk>,
Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
Matthew Auld <matthew.auld@intel.com>,
Eero Tamminen <eero.t.tamminen@intel.com>,
Rodrigo Vivi <rodrigo.vivi@intel.com>
Subject: Re: [Intel-gfx] [PATCH 2/2] drm/i915: Use Transparent Hugepages when IOMMU is enabled
Date: Fri, 3 Sep 2021 13:47:52 +0100 [thread overview]
Message-ID: <c8aecd1e-f6d6-cec2-3352-e01c9427248b@linux.intel.com> (raw)
In-Reply-To: <CAKMK7uE412nf5RisGBR2GrNsvgPH+omHv4K+m5McJv1t55DQMQ@mail.gmail.com>
On 29/07/2021 15:06, Daniel Vetter wrote:
> On Thu, Jul 29, 2021 at 3:34 PM Tvrtko Ursulin
> <tvrtko.ursulin@linux.intel.com> wrote:
>>
>> 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 just do that.
>>
>> 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% (IOMMU on versus
>> IOMMU off) to ~2% (same comparison but with THP on).
>>
>> v2:
>> * Add Kconfig dependency to transparent hugepages and some help text.
>> * Move to helper for easier handling of kernel build options.
>>
>> v3:
>> * Drop Kconfig. (Daniel)
>>
>> 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>
>> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
>> Cc: Daniel Vetter <daniel@ffwll.ch>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com> # v1
>
> On both patches: Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Eero's testing results at
https://gitlab.freedesktop.org/drm/intel/-/issues/430 are looking good -
seem to show this to be a net win for at least Gen9 and Gen12 platforms.
Is the ack enough to merge in this case or I should look for an r-b as well?
Regards,
Tvrtko
>> ---
>> drivers/gpu/drm/i915/gem/i915_gemfs.c | 22 +++++++++++++++++++---
>> 1 file changed, 19 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gemfs.c b/drivers/gpu/drm/i915/gem/i915_gemfs.c
>> index 5e6e8c91ab38..dbdbdc344d87 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gemfs.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gemfs.c
>> @@ -6,7 +6,6 @@
>>
>> #include <linux/fs.h>
>> #include <linux/mount.h>
>> -#include <linux/pagemap.h>
>>
>> #include "i915_drv.h"
>> #include "i915_gemfs.h"
>> @@ -15,6 +14,7 @@ int i915_gemfs_init(struct drm_i915_private *i915)
>> {
>> struct file_system_type *type;
>> struct vfsmount *gemfs;
>> + char *opts;
>>
>> type = get_fs_type("tmpfs");
>> if (!type)
>> @@ -26,10 +26,26 @@ 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+.
>> */
>>
>> - gemfs = kern_mount(type);
>> + opts = NULL;
>> + if (intel_vtd_active()) {
>> + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
>> + static char huge_opt[] = "huge=within_size"; /* r/w */
>> +
>> + opts = huge_opt;
>> + drm_info(&i915->drm,
>> + "Transparent Hugepage mode '%s'\n",
>> + opts);
>> + } else {
>> + drm_notice(&i915->drm,
>> + "Transparent Hugepage support is recommended for optimal performance when IOMMU is enabled!\n");
>> + }
>> + }
>> +
>> + gemfs = vfs_kern_mount(type, SB_KERNMOUNT, type->name, opts);
>> if (IS_ERR(gemfs))
>> return PTR_ERR(gemfs);
>>
>> --
>> 2.30.2
>>
>
>
next prev parent reply other threads:[~2021-09-03 12:48 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-29 13:34 [Intel-gfx] [PATCH 1/2] drm/i915/selftests: fixup igt_shrink_thp Tvrtko Ursulin
2021-07-29 13:34 ` [Intel-gfx] [PATCH 2/2] drm/i915: Use Transparent Hugepages when IOMMU is enabled Tvrtko Ursulin
2021-07-29 14:06 ` Daniel Vetter
2021-09-03 12:47 ` Tvrtko Ursulin [this message]
2021-09-07 8:42 ` Daniel Vetter
2021-09-07 9:34 ` Tvrtko Ursulin
2021-07-29 14:01 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for series starting with [1/2] drm/i915/selftests: fixup igt_shrink_thp Patchwork
2021-07-29 14:29 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2021-07-29 23:16 ` [Intel-gfx] ✓ Fi.CI.IGT: " Patchwork
-- strict thread matches above, loose matches on Subject: below --
2021-07-29 11:18 [Intel-gfx] [PATCH 1/2] " Tvrtko Ursulin
2021-07-29 11:18 ` [Intel-gfx] [PATCH 2/2] drm/i915: Use Transparent Hugepages when IOMMU is enabled Tvrtko Ursulin
2021-07-29 12:07 ` Daniel Vetter
2021-07-29 12:21 ` Tvrtko Ursulin
2021-07-29 12:28 ` Daniel Vetter
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