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authorGeorge Spelvin <lkml@sdf.org>2019-05-15 01:42:55 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-15 05:52:49 +0300
commit8fb583c4258d08f0aff105aa2ae5157b7d414ea2 (patch)
treed45dd566badd42d1c13507ea01e890e07dd0ade3 /mm/ksm.c
parent22a241ccb2c19962a0fb02c98154aa93d3fc1862 (diff)
downloadlinux-8fb583c4258d08f0aff105aa2ae5157b7d414ea2.tar.xz
lib/sort: avoid indirect calls to built-in swap
Similar to what's being done in the net code, this takes advantage of the fact that most invocations use only a few common swap functions, and replaces indirect calls to them with (highly predictable) conditional branches. (The downside, of course, is that if you *do* use a custom swap function, there are a few extra predicted branches on the code path.) This actually *shrinks* the x86-64 code, because it inlines the various swap functions inside do_swap, eliding function prologues & epilogues. x86-64 code size 767 -> 703 bytes (-64) Link: http://lkml.kernel.org/r/d10c5d4b393a1847f32f5b26f4bbaa2857140e1e.1552704200.git.lkml@sdf.org Signed-off-by: George Spelvin <lkml@sdf.org> Acked-by: Andrey Abramov <st5pub@yandex.ru> Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Daniel Wagner <daniel.wagner@siemens.com> Cc: Dave Chinner <dchinner@redhat.com> Cc: Don Mullis <don.mullis@gmail.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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