Tell the world we gave up on pushing CC_OPTIMIZE_FOR_SIZE

Kirill Smelkov · torvalds · commit 3a55fb0d9fe8 · 2013-01-16T12:42:57.000-08:00
In commit 281dc5c ("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>
diff --git 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
