Simplify the pool allocation code somewhat by merging loop arguments
used by multiple functions together in a struct and simplifying the
loop. Also add documentation.
This hopefully makes the behaviour of the allocation loop
simplier to understand, but above all paves the way for upcoming
restore-while-allocating functionality.
There are no functional changes, but the "allow_pools" bool
introduced to keep current functionality could be removed as a
follow up, which would enable using write-back cached pools when
allocating memory for other caching modes, rather than to resort
to allocating from the system directly.
v15:
- Introduce this patch to simplify the upcoming patch that introduces
restore while allocating.
Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/ttm/ttm_pool.c | 183 +++++++++++++++++++--------------
1 file changed, 108 insertions(+), 75 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
index 8504dbe19c1a..c9eba76d5143 100644
--- a/drivers/gpu/drm/ttm/ttm_pool.c
+++ b/drivers/gpu/drm/ttm/ttm_pool.c
@@ -58,6 +58,23 @@ struct ttm_pool_dma {
unsigned long vaddr;
};
+/**
+ * struct ttm_pool_alloc_state - Current state of the tt page allocation process
+ * @pages: Pointer to the next tt page pointer to populate.
+ * @caching_divide: Pointer to the first page pointer whose page has a staged but
+ * not committed caching transition from write-back to @tt_caching.
+ * @dma_addr: Pointer to the next tt dma_address entry to populate if any.
+ * @remaining_pages: Remaining pages to populate.
+ * @tt_caching: The requested cpu-caching for the pages allocated.
+ */
+struct ttm_pool_alloc_state {
+ struct page **pages;
+ struct page **caching_divide;
+ dma_addr_t *dma_addr;
+ pgoff_t remaining_pages;
+ enum ttm_caching tt_caching;
+};
+
static unsigned long page_pool_size;
MODULE_PARM_DESC(page_pool_size, "Number of pages in the WC/UC/DMA pool");
@@ -160,25 +177,25 @@ static void ttm_pool_free_page(struct ttm_pool *pool, enum ttm_caching caching,
kfree(dma);
}
-/* Apply a new caching to an array of pages */
-static int ttm_pool_apply_caching(struct page **first, struct page **last,
- enum ttm_caching caching)
+/* Apply any cpu-caching deferred during page allocation */
+static int ttm_pool_apply_caching(struct ttm_pool_alloc_state *alloc)
{
#ifdef CONFIG_X86
- unsigned int num_pages = last - first;
+ unsigned int num_pages = alloc->pages - alloc->caching_divide;
if (!num_pages)
return 0;
- switch (caching) {
+ switch (alloc->tt_caching) {
case ttm_cached:
break;
case ttm_write_combined:
- return set_pages_array_wc(first, num_pages);
+ return set_pages_array_wc(alloc->caching_divide, num_pages);
case ttm_uncached:
- return set_pages_array_uc(first, num_pages);
+ return set_pages_array_uc(alloc->caching_divide, num_pages);
}
#endif
+ alloc->caching_divide = alloc->pages;
return 0;
}
@@ -354,24 +371,41 @@ static unsigned int ttm_pool_page_order(struct ttm_pool *pool, struct page *p)
return p->private;
}
-/* Called when we got a page, either from a pool or newly allocated */
+/*
+ * Called when we got a page, either from a pool or newly allocated.
+ * if needed, dma map the page and populate the dma address array.
+ * Populate the page address array.
+ * If the caching is consistent, update any deferred caching. Otherwise
+ * stage this page for an upcoming deferred caching update.
+ */
static int ttm_pool_page_allocated(struct ttm_pool *pool, unsigned int order,
- struct page *p, dma_addr_t **dma_addr,
- unsigned long *num_pages,
- struct page ***pages)
+ struct page *p, enum ttm_caching page_caching,
+ struct ttm_pool_alloc_state *alloc)
{
- unsigned int i;
- int r;
+ pgoff_t i, nr = 1UL << order;
+ bool caching_consistent;
+ int r = 0;
+
+ caching_consistent = (page_caching == alloc->tt_caching) || PageHighMem(p);
+
+ if (caching_consistent) {
+ r = ttm_pool_apply_caching(alloc);
+ if (r)
+ return r;
+ }
- if (*dma_addr) {
- r = ttm_pool_map(pool, order, p, dma_addr);
+ if (alloc->dma_addr) {
+ r = ttm_pool_map(pool, order, p, &alloc->dma_addr);
if (r)
return r;
}
- *num_pages -= 1 << order;
- for (i = 1 << order; i; --i, ++(*pages), ++p)
- **pages = p;
+ alloc->remaining_pages -= nr;
+ for (i = 0; i < nr; ++i)
+ *alloc->pages++ = p++;
+
+ if (caching_consistent)
+ alloc->caching_divide = alloc->pages;
return 0;
}
@@ -413,6 +447,26 @@ static void ttm_pool_free_range(struct ttm_pool *pool, struct ttm_tt *tt,
}
}
+static void ttm_pool_alloc_state_init(const struct ttm_tt *tt,
+ struct ttm_pool_alloc_state *alloc)
+{
+ alloc->pages = tt->pages;
+ alloc->caching_divide = tt->pages;
+ alloc->dma_addr = tt->dma_address;
+ alloc->remaining_pages = tt->num_pages;
+ alloc->tt_caching = tt->caching;
+}
+
+/*
+ * Find a suitable allocation order based on highest desired order
+ * and number of remaining pages
+ */
+static unsigned int ttm_pool_alloc_find_order(unsigned int highest,
+ const struct ttm_pool_alloc_state *alloc)
+{
+ return min_t(unsigned int, highest, __fls(alloc->remaining_pages));
+}
+
/**
* ttm_pool_alloc - Fill a ttm_tt object
*
@@ -428,19 +482,19 @@ static void ttm_pool_free_range(struct ttm_pool *pool, struct ttm_tt *tt,
int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
struct ttm_operation_ctx *ctx)
{
- pgoff_t num_pages = tt->num_pages;
- dma_addr_t *dma_addr = tt->dma_address;
- struct page **caching = tt->pages;
- struct page **pages = tt->pages;
+ struct ttm_pool_alloc_state alloc;
enum ttm_caching page_caching;
gfp_t gfp_flags = GFP_USER;
pgoff_t caching_divide;
unsigned int order;
+ bool allow_pools;
struct page *p;
int r;
- WARN_ON(!num_pages || ttm_tt_is_populated(tt));
- WARN_ON(dma_addr && !pool->dev);
+ ttm_pool_alloc_state_init(tt, &alloc);
+
+ WARN_ON(!alloc.remaining_pages || ttm_tt_is_populated(tt));
+ WARN_ON(alloc.dma_addr && !pool->dev);
if (tt->page_flags & TTM_TT_FLAG_ZERO_ALLOC)
gfp_flags |= __GFP_ZERO;
@@ -453,67 +507,46 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
else
gfp_flags |= GFP_HIGHUSER;
- for (order = min_t(unsigned int, MAX_PAGE_ORDER, __fls(num_pages));
- num_pages;
- order = min_t(unsigned int, order, __fls(num_pages))) {
+ page_caching = tt->caching;
+ allow_pools = true;
+ for (order = ttm_pool_alloc_find_order(MAX_PAGE_ORDER, &alloc);
+ alloc.remaining_pages;
+ order = ttm_pool_alloc_find_order(order, &alloc)) {
struct ttm_pool_type *pt;
- page_caching = tt->caching;
- pt = ttm_pool_select_type(pool, tt->caching, order);
- p = pt ? ttm_pool_type_take(pt) : NULL;
- if (p) {
- r = ttm_pool_apply_caching(caching, pages,
- tt->caching);
- if (r)
- goto error_free_page;
-
- caching = pages;
- do {
- r = ttm_pool_page_allocated(pool, order, p,
- &dma_addr,
- &num_pages,
- &pages);
- if (r)
- goto error_free_page;
-
- caching = pages;
- if (num_pages < (1 << order))
- break;
-
- p = ttm_pool_type_take(pt);
- } while (p);
- }
-
- page_caching = ttm_cached;
- while (num_pages >= (1 << order) &&
- (p = ttm_pool_alloc_page(pool, gfp_flags, order))) {
-
- if (PageHighMem(p)) {
- r = ttm_pool_apply_caching(caching, pages,
- tt->caching);
- if (r)
- goto error_free_page;
- caching = pages;
- }
- r = ttm_pool_page_allocated(pool, order, p, &dma_addr,
- &num_pages, &pages);
- if (r)
- goto error_free_page;
- if (PageHighMem(p))
- caching = pages;
+ /* First, try to allocate a page from a pool if one exists. */
+ p = NULL;
+ pt = ttm_pool_select_type(pool, page_caching, order);
+ if (pt && allow_pools)
+ p = ttm_pool_type_take(pt);
+ /*
+ * If that fails or previously failed, allocate from system.
+ * Note that this also disallows additional pool allocations using
+ * write-back cached pools of the same order. Consider removing
+ * that behaviour.
+ */
+ if (!p) {
+ page_caching = ttm_cached;
+ allow_pools = false;
+ p = ttm_pool_alloc_page(pool, gfp_flags, order);
}
-
+ /* If that fails, lower the order if possible and retry. */
if (!p) {
if (order) {
--order;
+ page_caching = tt->caching;
+ allow_pools = true;
continue;
}
r = -ENOMEM;
goto error_free_all;
}
+ r = ttm_pool_page_allocated(pool, order, p, page_caching, &alloc);
+ if (r)
+ goto error_free_page;
}
- r = ttm_pool_apply_caching(caching, pages, tt->caching);
+ r = ttm_pool_apply_caching(&alloc);
if (r)
goto error_free_all;
@@ -523,10 +556,10 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
ttm_pool_free_page(pool, page_caching, order, p);
error_free_all:
- num_pages = tt->num_pages - num_pages;
- caching_divide = caching - tt->pages;
+ caching_divide = alloc.caching_divide - tt->pages;
ttm_pool_free_range(pool, tt, tt->caching, 0, caching_divide);
- ttm_pool_free_range(pool, tt, ttm_cached, caching_divide, num_pages);
+ ttm_pool_free_range(pool, tt, ttm_cached, caching_divide,
+ tt->num_pages - alloc.remaining_pages);
return r;
}
--
2.47.1
