Re: [Intel-gfx] [PATCH 5/7] drm/i915/guc: Use streaming loads to speed up dumping the guc log

Teres Alexis, Alan Previn
2022-08-02T18:48:47Z

One concern below. Else, nice, simple yet good optimization here. :)

In the interest of quicker progression, I will provide a conditional R-B if you can either fix the issue raised below on
the way in or provide a reason why that's not an issue:

Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>

On Wed, 2022-07-27 at 19:20 -0700, John.C.Harrison@Intel.com wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
>
> Use a temporary page and mempy_from_wc to reduce the time it takes to
> dump the guc log to debugfs.
>
> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
> Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
> ---
> drivers/gpu/drm/i915/gt/uc/intel_guc_log.c | 24 ++++++++++++++++------
> 1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_log.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_log.c
> index 07d31ae32f765..4722d4b18ed19 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_log.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_log.c
> @@ -750,8 +750,9 @@ int intel_guc_log_dump(struct intel_guc_log *log, struct drm_printer *p,
> struct intel_guc *guc = log_to_guc(log);
> struct intel_uc *uc = container_of(guc, struct intel_uc, guc);
> struct drm_i915_gem_object *obj = NULL;
> - u32 *map;
> - int i = 0;
> + void *map;
> + u32 *page;
> + int i, j;
>
> if (!intel_guc_is_supported(guc))
> return -ENODEV;
> @@ -764,23 +765,34 @@ int intel_guc_log_dump(struct intel_guc_log *log, struct drm_printer *p,
> if (!obj)
> return 0;
>
> + page = (u32 *)__get_free_page(GFP_KERNEL);
> + if (!page)
> + return -ENOMEM;

Alan: although unlikely, its possible that user could trigger debugfs mid of a gt reset - not sure if we need to use the
"uc->reset_in_progress" before calling this allocation and return a different error in that case like EAGAIN or EBUSY or
ECONNRESET.

> +
> intel_guc_dump_time_info(guc, p);
>
> map = i915_gem_object_pin_map_unlocked(obj, I915_MAP_WC);
> if (IS_ERR(map)) {
> DRM_DEBUG("Failed to pin object\n");
> drm_puts(p, "(log data unaccessible)\n");
> + free_page((unsigned long)page);
> return PTR_ERR(map);
> }
>
> - for (i = 0; i < obj->base.size / sizeof(u32); i += 4)
> - drm_printf(p, "0x%08x 0x%08x 0x%08x 0x%08x\n",
> - *(map + i), *(map + i + 1),
> - *(map + i + 2), *(map + i + 3));
> + for (i = 0; i < obj->base.size; i += PAGE_SIZE) {
> + if (!i915_memcpy_from_wc(page, map + i, PAGE_SIZE))
> + memcpy(page, map + i, PAGE_SIZE);
> +
> + for (j = 0; j < PAGE_SIZE / sizeof(u32); j += 4)
> + drm_printf(p, "0x%08x 0x%08x 0x%08x 0x%08x\n",
> + *(page + j + 0), *(page + j + 1),
> + *(page + j + 2), *(page + j + 3));
> + }
>
> drm_puts(p, "\n");
>
> i915_gem_object_unpin_map(obj);
> + free_page((unsigned long)page);
>
> return 0;
> }
> --
> 2.37.1
>