Console output oddity

Console output oddity

[Keith Fielding]

I have noticed a very odd behaviour when I am sending a large amount of
output to the console screen.
If I "cat" a large text file in a bash window it takes about 20 times
longer than if I "type" the same file in a DOS window. If I press and
hold down the CONTROL, SHIFT or ALT key as soon as the "cat" is started
then it runs about 4 times as fast. (If I hold the key down while
starting the "cat" it runs at the lower speed but the speed increases if
I release the key and then press it again.)
A simple C program which just loops printing a counter to stdout can be
speeded up by a factor of about 4 by holding down a key while it runs.
It can be speeded up by a factor of about 20 by compiling it with the
"-mno-cygwin" switch.
Can anyone offer an explanation?
-- 
Keith Fielding

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Re: Console output oddity

[Jonas Jensen]

----- Original Message -----
From: "Keith Fielding" <keithf@gaast.demon.co.uk>
To: <cygwin@sourceware.cygnus.com>
Sent: Wednesday, September 27, 2000 10:01 PM
Subject: Console output oddity


> I have noticed a very odd behaviour when I am sending a large amount of
> output to the console screen.
> If I "cat" a large text file in a bash window it takes about 20 times
> longer than if I "type" the same file in a DOS window. If I press and
> hold down the CONTROL, SHIFT or ALT key as soon as the "cat" is started
> then it runs about 4 times as fast. (If I hold the key down while
> starting the "cat" it runs at the lower speed but the speed increases if
> I release the key and then press it again.)
> A simple C program which just loops printing a counter to stdout can be
> speeded up by a factor of about 4 by holding down a key while it runs.
> It can be speeded up by a factor of about 20 by compiling it with the
> "-mno-cygwin" switch.
> Can anyone offer an explanation?

I reported this problem some time ago, I think the topic was called "printf
is faster when piped through tee". I can't reproduce the effects you talk
about when holding a key, on my system (W2k) cat is actually marginally
faster than type.
The C program that you can speed up with -mno-cygwin can get almost the same
speed increase if piped through cat or tee.

AFAIK, the problem was never fixed -- "Patches are Gratefully ConsideredT",
but I can't fix it and nobody else seems to care...

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Re: Console output oddity

[Chris Faylor]

On Sun, Oct 01, 2000 at 03:17:15AM +0200, Jonas Jensen wrote:
>>I have noticed a very odd behaviour when I am sending a large amount of
>>output to the console screen.
>>If I "cat" a large text file in a bash window it takes about 20 times
>>longer than if I "type" the same file in a DOS window.  If I press and
>>hold down the CONTROL, SHIFT or ALT key as soon as the "cat" is started
>>then it runs about 4 times as fast.  (If I hold the key down while
>>starting the "cat" it runs at the lower speed but the speed increases
>>if I release the key and then press it again.) A simple C program which
>>just loops printing a counter to stdout can be speeded up by a factor
>>of about 4 by holding down a key while it runs.  It can be speeded up
>>by a factor of about 20 by compiling it with the "-mno-cygwin" switch.
>>Can anyone offer an explanation?
>
>I reported this problem some time ago, I think the topic was called
>"printf is faster when piped through tee".  I can't reproduce the
>effects you talk about when holding a key, on my system (W2k) cat is
>actually marginally faster than type.  The C program that you can speed
>up with -mno-cygwin can get almost the same speed increase if piped
>through cat or tee.
>
>AFAIK, the problem was never fixed -- "Patches are Gratefully
>ConsideredT", but I can't fix it and nobody else seems to care...

I would certainly care to have any patch that speeds up any aspect of
Cygwin.

However, if you are referring to slowness when using the CYGWIN=tty
setting, then you should notice considerable speedups in recent cygwin
snapshots.

cgf

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