Adrian Bunk a écrit :
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.
You seem to to be confused between speed micro-otimizations and memory
savings. This patch has nothing to do about a speed optimization. Here, no
tradeoff justify a "measurable performance improvement" study.
I copied this patch to you because your recent proposal to remove read_mostly
from linux kernel.
Only you find read_mostly ugly and unmaintanable. I find it way more usefull
than "static" attributes.
I find 120 bytes is a measurable gain, thank you.
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