Re: [PATCH] blkdev: use an efficient way to check merge flags

2014-04-03 Thread Jianyu Zhan
Hi, Jan, I've just renewed the patch as you suggusted. Actually it isn't quite performance sensitive, but the point is one less branch leads to less penalty caused by branch prediction failure. Ok, this may be way too paranoid.:-) A bitwise flag comparison could be done using a more efficient b

Re: [PATCH] blkdev: use an efficient way to check merge flags

2014-04-03 Thread Jan Kara
On Thu 03-04-14 16:00:44, Zhan Jianyu wrote: > On Thu, Apr 3, 2014 at 2:13 AM, Jan Kara wrote: > > OK, but have you checked the generated code is actually any better? This > > is something I'd expect a compiler might be able to optimize anyway. And the > > original code looks more readable to me

Re: [PATCH] blkdev: use an efficient way to check merge flags

2014-04-03 Thread Zhan Jianyu
On Thu, Apr 3, 2014 at 2:13 AM, Jan Kara wrote: > OK, but have you checked the generated code is actually any better? This > is something I'd expect a compiler might be able to optimize anyway. And the > original code looks more readable to me. Hi, Jan, I've disassemble the code on my x86_64 b

Re: [PATCH] blkdev: use an efficient way to check merge flags

2014-04-02 Thread Jan Kara
On Wed 02-04-14 23:19:06, Jianyu Zhan wrote: > A bitwise flag comparison could be done using a more efficient bit-ops way. OK, but have you checked the generated code is actually any better? This is something I'd expect a compiler might be able to optimize anyway. And the original code looks more

[PATCH] blkdev: use an efficient way to check merge flags

2014-04-02 Thread Jianyu Zhan
A bitwise flag comparison could be done using a more efficient bit-ops way. Signed-off-by: Jianyu Zhan --- include/linux/blkdev.h | 13 +++-- 1 file changed, 3 insertions(+), 10 deletions(-) diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 1e1fa3f..adfa40a 100644 --- a