On Wed, Feb 17, 2021 at 08:05:06PM -0800, Yury Norov wrote:

This series introduces fast paths for find_bit() routines. It is
beneficial for typical systems, but those who limited in I-cache
may be concerned about increasing the .text size of the Image.

To address this concern, one can disable FAST_PATH option in the config
and some save memory.

The effect of this option on my arm64 next-20210217 build is:

(Maybe bloat-o-meter will give better view on this, i.e. more human-readable)

Before:
	Sections:
	Idx Name          Size      VMA               LMA               File off  Algn
	  0 .head.text    00010000  ffff800010000000  ffff800010000000  00010000  2**16
			  CONTENTS, ALLOC, LOAD, READONLY, CODE
	  1 .text         0115e3a8  ffff800010010000  ffff800010010000  00020000  2**16
			  CONTENTS, ALLOC, LOAD, READONLY, CODE
	  2 .got.plt      00000018  ffff80001116e3a8  ffff80001116e3a8  0117e3a8  2**3
			  CONTENTS, ALLOC, LOAD, DATA
	  3 .rodata       007a72ca  ffff800011170000  ffff800011170000  01180000  2**12
			  CONTENTS, ALLOC, LOAD, DATA
	  ...

After:
	Sections:
	Idx Name          Size      VMA               LMA               File off  Algn
	  0 .head.text    00010000  ffff800010000000  ffff800010000000  00010000  2**16
			  CONTENTS, ALLOC, LOAD, READONLY, CODE
	  1 .text         011623a8  ffff800010010000  ffff800010010000  00020000  2**16
			  CONTENTS, ALLOC, LOAD, READONLY, CODE
	  2 .got.plt      00000018  ffff8000111723a8  ffff8000111723a8  011823a8  2**3
			  CONTENTS, ALLOC, LOAD, DATA
	  3 .rodata       007a772a  ffff800011180000  ffff800011180000  01190000  2**12
			  CONTENTS, ALLOC, LOAD, DATA
	  ...

Notice that this is the cumulive effect on already existing fast paths
controlled by SMALL_CONST() together with ones added by this series.

...

+config FAST_PATH

I think the name is to broad for this cases, perhaps BITS_FAST_PATH? or BITMAP?

+	bool "Enable fast path code generation"
+	default y
+	help
+	  This option enables fast path optimization with the cost of increasing
+	  the text section.

-- 
With Best Regards,
Andy Shevchenko