path: root/mm
diff options
authorSean O. Stalley <sean.stalley@intel.com>2015-09-08 15:02:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-09-08 15:35:28 -0700
commitfa23f56d90ed7bd760ae2aea6dfb2f501a099e90 (patch)
tree3c747a07b47354302ada3df61943552ce09815f8 /mm
parentc54839a722a02818677bcabe57e957f0ce4f841d (diff)
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 <sean.stalley@intel.com> Acked-by: David Rientjes <rientjes@google.com> Cc: Vinod Koul <vinod.koul@intel.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Gilles Muller <Gilles.Muller@lip6.fr> Cc: Nicolas Palix <nicolas.palix@imag.fr> Cc: Michal Marek <mmarek@suse.cz> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
1 files 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,
- memset(retval, POOL_POISON_ALLOCATED, pool->size);
+ if (!(mem_flags & __GFP_ZERO))
+ memset(retval, POOL_POISON_ALLOCATED, pool->size);
spin_unlock_irqrestore(&pool->lock, flags);
+ if (mem_flags & __GFP_ZERO)
+ memset(retval, 0, pool->size);
return retval;