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| author | Kirill Smelkov <kirr@mns.spb.ru> | 2012-11-02 15:41:01 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-01-16 12:42:57 -0800 |
| commit | 3a55fb0d9fe8e2f4594329edd58c5fd6f35a99dd (patch) | |
| tree | 7198833c5bc3e7aac4b2a23282c2c4a09eae85d2 /init | |
| parent | fbfc23ef905e41cbf621031a3d560a55a010dd54 (diff) | |
| download | lwn-3a55fb0d9fe8e2f4594329edd58c5fd6f35a99dd.tar.gz lwn-3a55fb0d9fe8e2f4594329edd58c5fd6f35a99dd.zip | |
Tell the world we gave up on pushing CC_OPTIMIZE_FOR_SIZE
In commit 281dc5c5ec0f ("Give up on pushing CC_OPTIMIZE_FOR_SIZE") we
already changed the actual default value, but the help-text still
suggested 'y'. Fix the help text too, for all the same reasons.
Sadly, -Os keeps on generating some very suboptimal code for certain
cases, to the point where any I$ miss upside is swamped by the downside.
The main ones are:
- using "rep movsb" for memcpy, even on CPU's where that is
horrendously bad for performance.
- not honoring branch prediction information, so any I$ footprint you
win from smaller code, you lose from less code density in the I$.
- using divide instructions when that is very expensive.
Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'init')
| -rw-r--r-- | init/Kconfig | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/init/Kconfig b/init/Kconfig index 7d30240e5bfe..be8b7f55312d 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1182,7 +1182,7 @@ config CC_OPTIMIZE_FOR_SIZE Enabling this option will pass "-Os" instead of "-O2" to gcc resulting in a smaller kernel. - If unsure, say Y. + If unsure, say N. config SYSCTL bool |