On 17/05/16 10:22, Tvrtko Ursulin wrote:
On 16/05/16 16:19, Dave Gordon wrote:The recently-added i915_gem_object_pin_map() can be further optimised for "small" objects. To facilitate this, and simplify the error paths before adding the new code, this patch pulls out the "mapping" part of the operation (involving local allocations which must be undone before return) into its own subfunction. The next patch will then insert the new optimisation into the middle of the now-separated subfunction. This reorganisation will probably not affect the generated code, as the compiler will most likely inline it anyway, but it makes the logical structure a bit clearer and easier to modify. v2: Restructure loop-over-pages & error check (Chris Wilson) v3: Add page count to debug messages (Chris Wilson) Convert WARN_ON() to GEM_BUG_ON() Signed-off-by: Dave Gordon <david.s.gordon@xxxxxxxxx> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/i915/i915_gem.c | 59 ++++++++++++++++++++++++++--------------- 1 file changed, 38 insertions(+), 21 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index aff386e..bbec429 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2398,6 +2398,43 @@ static void i915_gem_object_free_mmap_offset(struct drm_i915_gem_object *obj) return 0; } +/* The 'mapping' part of i915_gem_object_pin_map() below */ +static void *i915_gem_object_map(const struct drm_i915_gem_object *obj) +{ + unsigned long n_pages = obj->base.size >> PAGE_SHIFT; + struct sg_table *sgt = obj->pages; + struct sg_page_iter sg_iter; + struct page **pages; + unsigned long i = 0; + void *addr = NULL;Looks like this does not need to be initialized?
OK. BTW the compiler didn't actually generate any code for this :)
+ + /* A single page can always be kmapped */ + if (n_pages == 1) + return kmap(sg_page(sgt->sgl)); + + pages = drm_malloc_gfp(n_pages, sizeof(*pages), GFP_TEMPORARY); + if (pages == NULL) { + DRM_DEBUG_DRIVER("Failed to get space for %lu pointers\n", + n_pages);Not terribly important but I think this is too low level functions to have debug logging. It will not add a lot of useful information, no call stack etc. And the callers are probably handling failures already and they would propagate somewhere from where it is already reported.+ return NULL; + } + + for_each_sg_page(sgt->sgl, &sg_iter, sgt->nents, 0) + pages[i++] = sg_page_iter_page(&sg_iter); + + /* Check that we have the expected number of pages */ + GEM_BUG_ON(i != n_pages); + + addr = vmap(pages, n_pages, 0, PAGE_KERNEL); + if (addr == NULL) + DRM_DEBUG_DRIVER("Failed to vmap %lu pages\n", n_pages);Same here. I mean, the only potential argument could be that this will tell the real reason which is otherwise lost in the NULL return code, but I am not sure it is worth it since it is so unlikely it would happen.
OK, debugging removed, new version posted. .Dave.
+ + drm_free_large(pages); + + return addr; +} + +/* get, pin, and map the pages of the object into kernel space */ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj) { int ret; @@ -2411,27 +2448,7 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj) i915_gem_object_pin_pages(obj); if (obj->mapping == NULL) { - struct page **pages; - - pages = NULL; - if (obj->base.size == PAGE_SIZE) - obj->mapping = kmap(sg_page(obj->pages->sgl)); - else - pages = drm_malloc_gfp(obj->base.size >> PAGE_SHIFT, - sizeof(*pages), - GFP_TEMPORARY); - if (pages != NULL) { - struct sg_page_iter sg_iter; - int n; - - n = 0; - for_each_sg_page(obj->pages->sgl, &sg_iter, - obj->pages->nents, 0) - pages[n++] = sg_page_iter_page(&sg_iter); - - obj->mapping = vmap(pages, n, 0, PAGE_KERNEL); - drm_free_large(pages); - } + obj->mapping = i915_gem_object_map(obj); if (obj->mapping == NULL) { i915_gem_object_unpin_pages(obj); return ERR_PTR(-ENOMEM);Otherwise looks fine to me. Regards, Tvrtko
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