From mboxrd@z Thu Jan  1 00:00:00 1970
From: Changli Gao <xiaosuo@gmail.com>
Subject: Re: [PATCH 2/2] fs: optimize mpage_bio_submit()
Date: Sat, 29 May 2010 21:33:02 +0800
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	<20100529124735.GB25092@liondog.tnic>
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To: Borislav Petkov <bp@alien8.de>, Changli Gao <xiaosuo@gmail.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
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On Sat, May 29, 2010 at 8:47 PM, Borislav Petkov <bp@alien8.de> wrote:
>
> ok, can you sincerely tell me that your change makes the code more
> readable? And have you checked to see what the compiler actually
> "optimizes"?
>
> original code:
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0movq =C2=A0 =C2=A0$mpage_end_io_read, %rdx=
 =C2=A0 =C2=A0 =C2=A0 =C2=A0#, tmp65
> =C2=A0 =C2=A0 =C2=A0 =C2=A0movq =C2=A0 =C2=A0$mpage_end_io_write, %ra=
x =C2=A0 =C2=A0 =C2=A0 #, tmp64
> =C2=A0 =C2=A0 =C2=A0 =C2=A0cmpl =C2=A0 =C2=A0$1, %edi =C2=A0 =C2=A0 =C2=
=A0 =C2=A0#, rw
> =C2=A0 =C2=A0 =C2=A0 =C2=A0cmovne =C2=A0%rdx, %rax =C2=A0 =C2=A0 =C2=A0=
# tmp65,, tmp64
> =C2=A0 =C2=A0 =C2=A0 =C2=A0movq =C2=A0 =C2=A0%rax, 80(%rsi) =C2=A0# t=
mp64, <variable>.bi_end_io
> =C2=A0 =C2=A0 =C2=A0 =C2=A0.loc 1 91 0
> =C2=A0 =C2=A0 =C2=A0 =C2=A0call =C2=A0 =C2=A0submit_bio =C2=A0 =C2=A0=
 =C2=A0#
>
> your change:
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0movq =C2=A0 =C2=A0$mpage_end_io_read, %rdx=
 =C2=A0 =C2=A0 =C2=A0 =C2=A0#, tmp63
> =C2=A0 =C2=A0 =C2=A0 =C2=A0movq =C2=A0 =C2=A0$mpage_end_io_write, %ra=
x =C2=A0 =C2=A0 =C2=A0 #, iftmp.561
> =C2=A0 =C2=A0 =C2=A0 =C2=A0cmpl =C2=A0 =C2=A0$1, %edi =C2=A0 =C2=A0 =C2=
=A0 =C2=A0#, rw
> =C2=A0 =C2=A0 =C2=A0 =C2=A0cmovne =C2=A0%rdx, %rax =C2=A0 =C2=A0 =C2=A0=
# tmp63,, iftmp.561
> =C2=A0 =C2=A0 =C2=A0 =C2=A0movq =C2=A0 =C2=A0%rax, 80(%rsi) =C2=A0# i=
ftmp.561, <variable>.bi_end_io
> =C2=A0 =C2=A0 =C2=A0 =C2=A0.loc 1 90 0
> =C2=A0 =C2=A0 =C2=A0 =C2=A0call =C2=A0 =C2=A0submit_bio =C2=A0 =C2=A0=
 =C2=A0#
>
> so that change does nothing except obfuscating the source a bit more =
so
> that you get more headaches whenever you look at it.
>

Oh, I didn't check the asm code. Compiler is smarter than I thought.
Thanks for your explaining.


--=20
Regards=EF=BC=8C
Changli Gao(xiaosuo@gmail.com)
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