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Date:   Fri, 19 Feb 2010 15:38:44 +0100
From:   Ralf Baechle <ralf@linux-mips.org>
To:     David Daney <ddaney@caviumnetworks.com>
Cc:     linux-mips@linux-mips.org
Subject: Re: [PATCH 0/3] MIPS vdso and signal delivery optimization (v2)
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 <20100219135727.GA15581@linux-mips.org>
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On Fri, Feb 19, 2010 at 02:57:27PM +0100, Ralf Baechle wrote:

> > Before:
> > n64 - Signal handler overhead: 14.517 microseconds
> > n32 - Signal handler overhead: 14.497 microseconds
> > o32 - Signal handler overhead: 16.637 microseconds
> > 
> > After:
> > 
> > n64 - Signal handler overhead: 7.935 microseconds
> > n32 - Signal handler overhead: 7.334 microseconds
> > o32 - Signal handler overhead: 8.628 microsecond
> 
> On a 180MHz 2 CPU single-node IP27:
> 
> Before:
> Signal handler installation: 3.524 microseconds
> Signal handler overhead: 37.009 microseconds
> Protection fault: 4.264 microseconds
> 
> After:
> Signal handler installation: 3.536 microseconds
> Signal handler overhead: 14.331 microseconds
> Protection fault: 3.600 microseconds
> 
> Everything meassured with very ancient O32 lmbench 2-alpha11 binaries.
> IP27 has processors in separate packages so the cache-to-cache overhead
> and thus the speedup is much higher than you have observed.

I dug up an old 2.6.12-rc1 kernel binary and reran lmbench on the same
system:

Signal handler installation: 4.207 microseconds
Signal handler overhead: 29.618 microseconds
Protection fault: 2.105 microseconds

And on 2.4.25:

Signal handler installation: 3.674 microseconds
Signal handler overhead: 8.855 microseconds
Protection fault: 3.159 microseconds

  Ralf