On Sun, Dec 16, 2007 at 12:45:01PM +0100, Eric Dumazet wrote:
> While examining vmlinux namelist on i686, I noticed :
>
> c0581300 D random_table
> c0581480 d input_pool
> c0581580 d random_read_wakeup_thresh
> c0581584 d random_write_wakeup_thresh
> c0581600 d blocking_pool
>
> That means that the two integers random_read_wakeup_thresh and
> random_write_wakeup_thresh use a full cache entry (128 bytes).
>
> Moving them to read_mostly section can shrinks vmlinux by 120 bytes.
>
> # size vmlinux*
> text data bss dec hex filename
> 4835553 450210 610304 5896067 59f783 vmlinux.after_patch
> 4835553 450330 610304 5896187 59f7fb vmlinux.before_patch
>
> Signed-off-by: Eric Dumazet <[email protected]>
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 5fee056..af48e86 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -256,14 +256,14 @@
> * The minimum number of bits of entropy before we wake up a read on
> * /dev/random. Should be enough to do a significant reseed.
> */
> -static int random_read_wakeup_thresh = 64;
> +static int random_read_wakeup_thresh __read_mostly = 64;
>
> /*
> * If the entropy count falls under this number of bits, then we
> * should wake up processes which are selecting or polling on write
> * access to /dev/random.
> */
> -static int random_write_wakeup_thresh = 128;
> +static int random_write_wakeup_thresh __read_mostly = 128;
Please never ever do such ugly and unmaintainable micro-optimizations in
the code unless you can show a measurable performance improvement of the
kernel.
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
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