Commit 098fb254 authored Aug 21, 2013 by Kent Overstreet

bcache: Delete some slower inline asm



Never saw a profile of bset_search_tree() where it wasn't bottlenecked
on memory until I got my new Haswell machine, but when I tried it there
it was suddenly burning 20% of the cpu in the inner loop on shrd...

Turns out, the version of shrd that takes 64 bit operands has a 9 cycle
latency. hah.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

parent 28935ab5

drivers/md/bcache/bset.c

+0 −8

Original line number	Diff line number	Diff line
		@@ -481,16 +481,8 @@ static struct bkey table_to_bkey(struct bset_tree t, unsigned cacheline)

		static inline uint64_t shrd128(uint64_t high, uint64_t low, uint8_t shift)
		{
		#ifdef CONFIG_X86_64
		asm("shrd %[shift],%[high],%[low]"
		: [low] "+Rm" (low)
		: [high] "R" (high),
		[shift] "ci" (shift)
		: "cc");
		#else
		low >>= shift;
		low \|= (high << 1) << (63U - shift);
		#endif
		return low;
		}