Messages in this thread | | | Date | Thu, 28 Feb 2008 19:29:24 +0100 | From | Jean Delvare <> | Subject | Re: [PATCH] video: limit stack usage of ir-kbd-i2c.c |
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On Wed, 27 Feb 2008 11:23:26 +0100, Marcin Slusarz wrote: > On Tue, Feb 26, 2008 at 11:23:20PM +0100, Jean Delvare wrote: > > * You can move the handling of some ioctls to dedicated functions, just > > like I did in i2c-dev: > > http://lists.lm-sensors.org/pipermail/i2c/2008-February/003010.html > > However there is a risk that gcc will inline these functions (that's > > what happened to me...) Not sure how to prevent gcc from inlining. > > There's "noinline" attribute in linux/compiler.h (compiler-gcc.h actually) > for these situations.
I didn't know about noinline, thanks for the tip. It works as expected, however in the case of i2cdev_ioctl I'm not sure if it's worth it. Without it, I have:
0x02ae i2cdev_ioctl [i2c-dev]: 192
With noinline, I have:
0x02ac i2cdev_ioctl_smbus [i2c-dev]: 112 0x05bc i2cdev_ioctl_rdrw [i2c-dev]: 112 0x087e i2cdev_ioctl [i2c-dev]: 32
32 + 112 = 144, 192 - 144 = only 48 bytes saved on the stack, at the price of some performance loss. OTOH this makes the binary slightly smaller (not sure why), which is always nice:
add/remove: 2/0 grow/shrink: 0/1 up/down: 1121/-1182 (-61) function old new delta i2cdev_ioctl_rdrw - 696 +696 i2cdev_ioctl_smbus - 425 +425 i2cdev_ioctl 1482 300 -1182
-- Jean Delvare
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