From e34f44b3517fe545f7fd45a8c2f6ee1e5e4432d3 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Mon, 3 Dec 2007 14:16:24 -0500 Subject: [PATCH] pool: Improve memory usage for devices which can't cross boundaries The previous implementation simply refused to allocate more than a boundary's worth of data from an entire page. Some users didn't know this, so specified things like SMP_CACHE_BYTES, not realising the horrible waste of memory that this was. It's fairly easy to correct this problem, just by ensuring we don't cross a boundary within a page. This even helps drivers like EHCI (which can't cross a 4k boundary) on machines with larger page sizes. Signed-off-by: Matthew Wilcox Acked-by: David S. Miller --- mm/dmapool.c | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) diff --git a/mm/dmapool.c b/mm/dmapool.c index 72e7ece7ee..34aaac451a 100644 --- a/mm/dmapool.c +++ b/mm/dmapool.c @@ -43,6 +43,7 @@ struct dma_pool { /* the pool */ size_t size; struct device *dev; size_t allocation; + size_t boundary; char name[32]; wait_queue_head_t waitq; struct list_head pools; @@ -107,7 +108,7 @@ static DEVICE_ATTR(pools, S_IRUGO, show_pools, NULL); * @dev: device that will be doing the DMA * @size: size of the blocks in this pool. * @align: alignment requirement for blocks; must be a power of two - * @allocation: returned blocks won't cross this boundary (or zero) + * @boundary: returned blocks won't cross this power of two boundary * Context: !in_interrupt() * * Returns a dma allocation pool with the requested characteristics, or @@ -117,15 +118,16 @@ static DEVICE_ATTR(pools, S_IRUGO, show_pools, NULL); * cache flushing primitives. The actual size of blocks allocated may be * larger than requested because of alignment. * - * If allocation is nonzero, objects returned from dma_pool_alloc() won't + * If @boundary is nonzero, objects returned from dma_pool_alloc() won't * cross that size boundary. This is useful for devices which have * addressing restrictions on individual DMA transfers, such as not crossing * boundaries of 4KBytes. */ struct dma_pool *dma_pool_create(const char *name, struct device *dev, - size_t size, size_t align, size_t allocation) + size_t size, size_t align, size_t boundary) { struct dma_pool *retval; + size_t allocation; if (align == 0) { align = 1; @@ -142,27 +144,26 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev, if ((size % align) != 0) size = ALIGN(size, align); - if (allocation == 0) { - if (PAGE_SIZE < size) - allocation = size; - else - allocation = PAGE_SIZE; - /* FIXME: round up for less fragmentation */ - } else if (allocation < size) + allocation = max_t(size_t, size, PAGE_SIZE); + + if (!boundary) { + boundary = allocation; + } else if ((boundary < size) || (boundary & (boundary - 1))) { return NULL; + } - if (! - (retval = - kmalloc_node(sizeof *retval, GFP_KERNEL, dev_to_node(dev)))) + retval = kmalloc_node(sizeof(*retval), GFP_KERNEL, dev_to_node(dev)); + if (!retval) return retval; - strlcpy(retval->name, name, sizeof retval->name); + strlcpy(retval->name, name, sizeof(retval->name)); retval->dev = dev; INIT_LIST_HEAD(&retval->page_list); spin_lock_init(&retval->lock); retval->size = size; + retval->boundary = boundary; retval->allocation = allocation; init_waitqueue_head(&retval->waitq); @@ -192,11 +193,14 @@ EXPORT_SYMBOL(dma_pool_create); static void pool_initialise_page(struct dma_pool *pool, struct dma_page *page) { unsigned int offset = 0; + unsigned int next_boundary = pool->boundary; do { unsigned int next = offset + pool->size; - if (unlikely((next + pool->size) >= pool->allocation)) - next = pool->allocation; + if (unlikely((next + pool->size) >= next_boundary)) { + next = next_boundary; + next_boundary += pool->boundary; + } *(int *)(page->vaddr + offset) = next; offset = next; } while (offset < pool->allocation); -- 2.39.5