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SubjectRe: [PATCH] ttm: add pool wc/uc page allocator
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On Thu, 2009-07-16 at 18:13 +0200, Jerome Glisse wrote:
> On AGP system we might allocate/free routinely uncached or wc memory,
> changing page from cached (wb) to uc or wc is very expensive and involves
> a lot of flushing. To improve performance this allocator use a pool
> of uc,wc pages.
>
> Currently each pool (wc, uc) is 256 pages big, improvement would be
> to tweak this according to memory pressure so we can give back memory
> to system.
>
> Signed-off-by: Dave Airlie <airlied@redhat.com>
> Signed-off-by: Jerome Glisse <jglisse@redhat.com>
> ---
> drivers/gpu/drm/ttm/Makefile | 2 +-
> drivers/gpu/drm/ttm/ttm_memory.c | 3 +
> drivers/gpu/drm/ttm/ttm_page_alloc.c | 342 ++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/ttm/ttm_page_alloc.h | 36 ++++
> drivers/gpu/drm/ttm/ttm_tt.c | 32 +---
> 5 files changed, 391 insertions(+), 24 deletions(-)
> create mode 100644 drivers/gpu/drm/ttm/ttm_page_alloc.c
> create mode 100644 drivers/gpu/drm/ttm/ttm_page_alloc.h

> +
> +
> +#ifdef CONFIG_X86
> +/* TODO: add this to x86 like _uc, this version here is inefficient */
> +static int set_pages_array_wc(struct page **pages, int addrinarray)
> +{
> + int i;
> +
> + for (i = 0; i < addrinarray; i++) {
> + set_memory_wc((unsigned long)page_address(pages[i]), 1);
> + }
> + return 0;
> +}
> +#else
> +static int set_pages_array_wb(struct page **pages, int addrinarray)
> +{
> +#ifdef TTM_HAS_AGP
> + int i;
> +
> + for (i = 0; i < addrinarray; i++) {
> + unmap_page_from_agp(pages[i]);
> + }
> +#endif
> + return 0;
> +}
> +
> +static int set_pages_array_wc(struct page **pages, int addrinarray)
> +{
> +#ifdef TTM_HAS_AGP
> + int i;
> +
> + for (i = 0; i < addrinarray; i++) {
> + map_page_into_agp(pages[i]);
> + }
> +#endif
> + return 0;
> +}
> +
> +static int set_pages_array_uc(struct page **pages, int addrinarray)
> +{
> +#ifdef TTM_HAS_AGP
> + int i;
> +
> + for (i = 0; i < addrinarray; i++) {
> + map_page_into_agp(pages[i]);
> + }
> +#endif
> + return 0;
> +}
> +#endif
> +
> +
> +void pages_free_locked(void)
> +{
> + int i;
> +
> + set_pages_array_wb(_pages, _npages_to_free);
> + for (i = 0; i < _npages_to_free; i++) {
> + __free_page(_pages[i]);
> + }
> + _npages_to_free = 0;
> +}
> +
> +static void ttm_page_pool_init_locked(struct page_pool *pool)
> +{
> + INIT_LIST_HEAD(&pool->list);
> + pool->npages = 0;
> +}
> +
> +static int page_pool_fill_locked(struct page_pool *pool,
> + enum ttm_caching_state cstate)
> +{
> + struct page *page;
> + int i, cpages;
> +
> + /* We need the _pages table to change page cache status so empty it */
> + if (cstate != tt_cached && _npages_to_free)
> + pages_free_locked();
> +
> + for (i = 0, cpages = 0; i < (NUM_PAGES_TO_ADD - pool->npages); i++) {
> + page = alloc_page(pool->gfp_flags);
> + if (!page) {
> + printk(KERN_ERR "unable to get page %d\n", i);
> + return -ENOMEM;
> + }
> +#ifdef CONFIG_X86
> + /* gfp flags of highmem page should never be dma32 so we
> + * we should be fine in such case
> + */
> + if (PageHighMem(page)) {
> + if (pool->gfp_flags & GFP_DMA32) {
> + list_add(&page->lru, &_hm_pool_dma32.list);
> + _hm_pool_dma32.npages++;
> + } else {
> + list_add(&page->lru, &_hm_pool.list);
> + _hm_pool.npages++;
> + }
> + } else
> +#endif
> + {
> + list_add(&page->lru, &pool->list);
> + pool->npages++;
> + _pages[i] = page;
> + cpages++;
> + }
> + }
> + switch(cstate) {
> + case tt_uncached:
> + set_pages_array_uc(_pages, cpages);
> + break;
> + case tt_wc:
> + set_pages_array_wc(_pages, cpages);
> + break;
> + case tt_cached:
> + default:
> + break;
> + }
> + return 0;
> +}
> +
> +static inline void ttm_page_put_locked(struct page *page)
> +{
> + if (_npages_to_free >= NUM_PAGES_TO_ADD)
> + pages_free_locked();
> + _pages[_npages_to_free++] = page;
> +}
> +
> +static void ttm_page_pool_empty_locked(struct page_pool *pool, bool hm)
> +{
> + struct page *page, *tmp;
> +
> + if (hm) {
> + list_for_each_entry_safe(page, tmp, &pool->list, lru) {
> + list_del(&page->lru);
> + __free_page(page);
> + }
> + } else {
> + list_for_each_entry_safe(page, tmp, &pool->list, lru) {
> + list_del(&page->lru);
> + ttm_page_put_locked(page);
> + }
> + }
> + pool->npages = 0;
> +}
> +
> +
> +struct page *ttm_get_page(int flags, enum ttm_caching_state cstate)
> +{
> + struct page_pool *pool;
> + struct page_pool *hm_pool;
> + struct page *page = NULL;
> + int gfp_flags = GFP_HIGHUSER;
> + int r;
> +
> + hm_pool = &_hm_pool;
> + if (flags & TTM_PAGE_FLAG_ZERO_ALLOC)
> + gfp_flags |= __GFP_ZERO;
> + if (flags & TTM_PAGE_FLAG_DMA32) {
> + gfp_flags |= GFP_DMA32;
> + hm_pool = &_hm_pool_dma32;
> + }

You remove my dma32 changes from my tree to fix this.
>
> -static struct page *ttm_tt_alloc_page(unsigned page_flags)
> -{
> - gfp_t gfp_flags = GFP_USER;
> -
> - if (page_flags & TTM_PAGE_FLAG_ZERO_ALLOC)
> - gfp_flags |= __GFP_ZERO;
> -
> - if (page_flags & TTM_PAGE_FLAG_DMA32)
> - gfp_flags |= __GFP_DMA32;
> - else
> - gfp_flags |= __GFP_HIGHMEM;
> -
> - return alloc_page(gfp_flags);
> -}

Note the differences? you can't say HIGHMEM and DMA32 as the
kernel points out with CONFIG_DEBUG_VM.

Dave.



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