• Sean O. Stalley's avatar
    mm: add support for __GFP_ZERO flag to dma_pool_alloc() · fa23f56d
    Sean O. Stalley authored
    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: 's avatarSean O. Stalley <sean.stalley@intel.com>
    Acked-by: 's avatarDavid 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: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    fa23f56d
dmapool.c 13.9 KB