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Subject: Re: readv/writev
From: Robert Collins <rbcollins AT cygwin DOT com>
To: Conrad Scott <Conrad DOT Scott AT dsl DOT pipex DOT com>
Cc: cygwin-developers AT cygwin DOT com
In-Reply-To: <019701c2494f$614e4a40$6132bc3e@BABEL>
References: <019701c2494f$614e4a40$6132bc3e AT BABEL>
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Date: 22 Aug 2002 09:06:34 +1000
Message-Id: <1029971194.28132.16.camel@lifelesswks>
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On Thu, 2002-08-22 at 06:14, Conrad Scott wrote:

>=20
> On my m/c, a 900Mhz Pentium III (?), the same test program I was
> using for the __stdcall / regparm testing (read 16Mb from
> /dev/zero one byte at a time and write to /dev/zero) takes about 3
> seconds longer with the readv/writev changes.  That is, ~38.6
> seconds rather than ~35.6 seconds.  So, it's measurable but it's a
> pretty extreme test.

how long does it take if you read in a readv block of, say 1000
elements? Faster or slower?
=20
> Does anyone feel this is important?  If so, I can write separate
> code paths for both read/write as well as readv/writev, which
> would then be no slower than the current DLL code.  The issue then
> is a small increase in DLL size along with more duplicate code to
> maintain.
>=20
> Any votes?

1) Implement a clean design.=20
2) *IF* the readv->read code is fairly short, put it in a header so it
can inline when appropriate.
3) Implement 'native' Overlapped IOw/  scatter-gather for NT OS's on
disk files. :}.

Rob

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