From: Kent Overstreet <kmo@daterainc.com>
Date: Thu, 22 Aug 2013 01:36:45 +0000 (-0700)
Subject: bcache: Delete some slower inline asm
X-Git-Tag: next-20130912~34^2~6^2~2
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=27698d6fbb5025c8a4427a7a50df9182dd5326b1;p=karo-tx-linux.git

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>
---

diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
index 6923be8db38c..3897a977428a 100644
--- a/drivers/md/bcache/bset.c
+++ b/drivers/md/bcache/bset.c
@@ -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;
 }