linux-kernel - Re: [GIT PULL] x86 fixes for 3.11-rc2

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Message-ID: <20130720144758.13924.qmail@science.horizon.com>
Date:	20 Jul 2013 10:47:58 -0400
From:	"George Spelvin" <linux@...izon.com>
To:	bp@...en8.de, linux@...izon.com
Cc:	hpa@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] x86 fixes for 3.11-rc2

Borislav Petkov <bp@...en8.de> wrote:
> I don't think that matters because this is called only once on suspend.
> Unless the cleaner assembly translates into a palpable speedup, which I
> doubt.

I was thinking about code *size*, actually; I agree that speed is
too small to measure.

Clean code (21 bytes):
  4e:   b9 80 00 00 c0          mov    $0xc0000080,%ecx
  53:   0f 32                   rdmsr  
  55:   0f 30                   wrmsr  
  57:   31 f6                   xor    %esi,%esi
  59:   85 f6                   test   %esi,%esi
  5b:   89 43 14                mov    %eax,0x14(%ebx)
  5e:   89 53 18                mov    %edx,0x18(%ebx)
  61:   75 04                   jne    67 <acpi_suspend_lowlevel+0x67>

Ugly code (50 bytes):
  51:   b9 80 00 00 c0          mov    $0xc0000080,%ecx
  56:   0f 32                   rdmsr  
  58:   31 c9                   xor    %ecx,%ecx
  5a:   89 c6                   mov    %eax,%esi
  5c:   85 c9                   test   %ecx,%ecx
  5e:   89 45 ec                mov    %eax,-0x14(%ebp)
  61:   89 55 f0                mov    %edx,-0x10(%ebp)
  64:   89 73 14                mov    %esi,0x14(%ebx)
  67:   89 53 18                mov    %edx,0x18(%ebx)
  6a:   75 1b                   jne    87 <acpi_suspend_lowlevel+0x87>
  6c:   8b 75 ec                mov    -0x14(%ebp),%esi
  6f:   b9 80 00 00 c0          mov    $0xc0000080,%ecx
  74:   8b 7d f0                mov    -0x10(%ebp),%edi
  77:   89 f0                   mov    %esi,%eax
  79:   89 fa                   mov    %edi,%edx
  7b:   0f 30                   wrmsr  
  7d:   31 c0                   xor    %eax,%eax
  7f:   85 c0                   test   %eax,%eax
  81:   75 04                   jne    87 <acpi_suspend_lowlevel+0x87>

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