lkml.org 
[lkml]   [2019]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] mod_devicetable.h: reduce sizeof(struct of_device_id) by 80 bytes
Date
A typical kernel image has hundreds of static struct of_device_id
instances (a lot of which are sentinel all-zeroes), each occupying
~200 bytes. Nobody initializes the .compatible member with strings
anywhere near 128 bytes, so a lot of that memory is simply wasted.

To verify, I first had the 0day bot chew on a patch adding a dummy
extremely long .compatible string, and I did get an email saying that
the patch resulted in lots of new
"warning:initializer-string-for-array-of-chars-is-too-long"
warnings. Then I had it chew on a version of this patch reducing to 46
(because gcc unfortunately does not warn when the literal sans the
terminating nul just fits), and got a SUCCESS mail listing 107
config/arch combinations.

For an arm imx_v6_v7_defconfig kernel, .rodata becomes 70K smaller;
.init.data shrinks by another ~13K, making the whole kernel image
about 83K, or 0.3%, smaller.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
include/linux/mod_devicetable.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index 448621c32e4d..502629bdac2e 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -241,7 +241,7 @@ struct sdw_device_id {
struct of_device_id {
char name[32];
char type[32];
- char compatible[128];
+ char compatible[48];
const void *data;
};

--
2.20.1
\
 
 \ /
  Last update: 2019-04-25 22:31    [W:0.065 / U:19.348 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site