Subject: Re: Time and motion studies of gcc and egcs and LCC
From: [email-masked] (Samuel James Liddicott)

3 Feb 1998 18:16:53 -0800
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-----Original Message-----
From: [email-masked] <[email-masked]>
To: [email-masked] <[email-masked]>
Date: 03 February 1998 04:02
Subject: Re: Time and motion studies of gcc and egcs and LCC

>I don't think that the overhead of getting into a DLL is all that great, so
>I think that the performance hit is somewhere else, like inside cygwin.dll
>and NT itself.  The cost to enter a DLL is an additional jump instruction
>(indirect through the linkage pointer).  To return is no cost.  Granted,
this
>does bring an additional page into the working set (or two, actually,
because
>the linkage pointer is probably on a different page), but if the calls are
>frequent, it should not be flushed frequently, so the page fault cost is
>not very great either.

I read that in win95 the pages are flushed in order of first-in-first-out,
and if a flushed page is a commonly used page, it will just be first-in
again a bit quicker, and all this to save on the overheads of working out
which pages are least used.

I was shocked when I read it too, but imagine the overheads of doing page
usage sorting every time you need to load a new page?  MS seemed to think
little was gained.

Sam Liddicott                   |   Nothing I say is to be attributed as |
Campbell Scientific Ltd.        | a company statement or representation. |
Campbell Park, 80 Hathern Road, *----------------------------------------+
Shepshed, Leic. United Kingdom. LE12 9AL        Phone: +44 (0) 1509 601141
Email: [email-masked]                    Fax:   +44 (0) 1509 601091

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