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Date: Sat, 24 Dec 2011 11:27:59 +0000
From: Alexander Best <arundel@freebsd.org>
To: Bruce Evans <brde@optusnet.com.au>
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Cc: freebsd-current@freebsd.org, freebsd-arch@freebsd.org
Subject: Re: [rfc] removing -mpreferred-stack-boundary=2 flag for i386?
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On Sat Dec 24 11, Bruce Evans wrote:
> On Sat, 24 Dec 2011, Alexander Best wrote:
> 
> >On Sat Dec 24 11, Bruce Evans wrote:
> >>On Fri, 23 Dec 2011, Alexander Best wrote:
> >>
> >>>is -mpreferred-stack-boundary=2 really necessary for i386 builds any
> >>>longer?
> >>>i built GENERIC (including modules) with and without that flag. the 
> >>>results
> >>>are:
> >>
> >>The same as it has always been.  It avoids some bloat.
> >>
> >>>1654496	bytes with the flag set
> >>>vs.
> >>>1654952	bytes with the flag unset
> >>
> >>I don't believe this.  GENERIC is enormously bloated, so it has size
> >>more like 16MB than 1.6MB.  Even a savings of 4K instead of 456 bytes
> >
> >i'm sorry. i used du(1) to get those numbers, so i believe those numbers
> >represent the ammount of 512-byte blocks. if i'm correct GENERIC is even
> >more bloated than you feared and almost reaches 1GB:
> >
> >807,859375  megabytes with flag set
> >vs.
> >808,0820313 megabytes without the flag set
> 
> That's certainly bloated.  It counts all object files and modules, and
> probably everything is compiled with -g.  I only counted kernel text
> size.

yeah, but for demonstrating the different size between the build with
-mpreferred-stack-boundary=2 set and -mpreferred-stack-boundary=2 unset, it
doesn't really matter how big the directories are and if object files are
included. the difference in size is < 1 megabyte. so setting
-mpreferred-stack-boundary=2 doesn't aid in reducing the kernel (or modules)
size, but merely to improve improve stack performance/efficiency.

cheers.
alex

> 
> Bruce