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authorNicolas Pitre <nicolas.pitre@linaro.org>2018-01-19 18:17:46 +0100
committerRussell King <rmk+kernel@armlinux.org.uk>2018-01-21 15:37:56 +0000
commitff5fdafc9e9702846480e0cea55ba861f72140a2 (patch)
tree28531d5acbc851bf5f210062bc9d0e08f1fee85e /drivers/dma
parentec80eb467171b511635b9e3086fec357f79afe3b (diff)
downloadblackbird-op-linux-ff5fdafc9e9702846480e0cea55ba861f72140a2.tar.gz
blackbird-op-linux-ff5fdafc9e9702846480e0cea55ba861f72140a2.zip
ARM: 8745/1: get rid of __memzero()
The __memzero assembly code is almost identical to memset's except for two orr instructions. The runtime performance of __memset(p, n) and memset(p, 0, n) is accordingly almost identical. However, the memset() macro used to guard against a zero length and to call __memzero at compile time when the fill value is a constant zero interferes with compiler optimizations. Arnd found tha the test against a zero length brings up some new warnings with gcc v8: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82103 And successively rremoving the test against a zero length and the call to __memzero optimization produces the following kernel sizes for defconfig with gcc 6: text data bss dec hex filename 12248142 6278960 413588 18940690 1210312 vmlinux.orig 12244474 6278960 413588 18937022 120f4be vmlinux.no_zero_test 12239160 6278960 413588 18931708 120dffc vmlinux.no_memzero So it is probably not worth keeping __memzero around given that the compiler can do a better job at inlining trivial memset(p,0,n) on its own. And the memset code already handles a zero length just fine. Suggested-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Nicolas Pitre <nico@linaro.org> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'drivers/dma')
-rw-r--r--drivers/dma/imx-dma.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
index 331f863c605e..715b39ae5a46 100644
--- a/drivers/dma/imx-dma.c
+++ b/drivers/dma/imx-dma.c
@@ -765,7 +765,7 @@ static int imxdma_alloc_chan_resources(struct dma_chan *chan)
desc = kzalloc(sizeof(*desc), GFP_KERNEL);
if (!desc)
break;
- __memzero(&desc->desc, sizeof(struct dma_async_tx_descriptor));
+ memset(&desc->desc, 0, sizeof(struct dma_async_tx_descriptor));
dma_async_tx_descriptor_init(&desc->desc, chan);
desc->desc.tx_submit = imxdma_tx_submit;
/* txd.flags will be overwritten in prep funcs */
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