From fa23f56d90ed7bd760ae2aea6dfb2f501a099e90 Mon Sep 17 00:00:00 2001 From: "Sean O. Stalley" Date: Tue, 8 Sep 2015 15:02:24 -0700 Subject: [PATCH] mm: add support for __GFP_ZERO flag to dma_pool_alloc() Currently a call to dma_pool_alloc() with a ___GFP_ZERO flag returns a non-zeroed memory region. This patchset adds support for the __GFP_ZERO flag to dma_pool_alloc(), adds 2 wrapper functions for allocing zeroed memory from a pool, and provides a coccinelle script for finding & replacing instances of dma_pool_alloc() followed by memset(0) with a single dma_pool_zalloc() call. There was some concern that this always calls memset() to zero, instead of passing __GFP_ZERO into the page allocator. [https://lkml.org/lkml/2015/7/15/881] I ran a test on my system to get an idea of how often dma_pool_alloc() calls into pool_alloc_page(). After Boot: [ 30.119863] alloc_calls:541, page_allocs:7 After an hour: [ 3600.951031] alloc_calls:9566, page_allocs:12 After copying 1GB file onto a USB drive: [ 4260.657148] alloc_calls:17225, page_allocs:12 It doesn't look like dma_pool_alloc() calls down to the page allocator very often (at least on my system). This patch (of 4): Currently the __GFP_ZERO flag is ignored by dma_pool_alloc(). Make dma_pool_alloc() zero the memory if this flag is set. Signed-off-by: Sean O. Stalley Acked-by: David Rientjes Cc: Vinod Koul Cc: Bjorn Helgaas Cc: Gilles Muller Cc: Nicolas Palix Cc: Michal Marek Cc: Sebastian Andrzej Siewior Cc: Jonathan Corbet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/dmapool.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/dmapool.c b/mm/dmapool.c index 4b657099111f..71a8998cd03a 100644 --- a/mm/dmapool.c +++ b/mm/dmapool.c @@ -337,7 +337,7 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags, /* pool_alloc_page() might sleep, so temporarily drop &pool->lock */ spin_unlock_irqrestore(&pool->lock, flags); - page = pool_alloc_page(pool, mem_flags); + page = pool_alloc_page(pool, mem_flags & (~__GFP_ZERO)); if (!page) return NULL; @@ -375,9 +375,14 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags, break; } } - memset(retval, POOL_POISON_ALLOCATED, pool->size); + if (!(mem_flags & __GFP_ZERO)) + memset(retval, POOL_POISON_ALLOCATED, pool->size); #endif spin_unlock_irqrestore(&pool->lock, flags); + + if (mem_flags & __GFP_ZERO) + memset(retval, 0, pool->size); + return retval; } EXPORT_SYMBOL(dma_pool_alloc); -- 2.39.5