linux-kernel - Re: RFD: x32 ABI system call numbers

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Message-ID: <20110830105637.35f9e46e@lxorguk.ukuu.org.uk>
Date:	Tue, 30 Aug 2011 10:56:37 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Kyle Moffett <kyle@...fetthome.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"H.J. Lu" <hjl.tools@...il.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: RFD: x32 ABI system call numbers

> > The only programs which really care are those which map many gigs
> > of stuff into memory (IE: big databases, etc). 
> 
> You mean anything that mmaps a file?
> 2-3GB is not a whole lot these days.

For most stuff its a lot, and most apps that mmap files mmap the bits
they need. O_LARGEFILE and 64bit time_t do make sense though.

> 2Gb is a very similar thing as Linus y2038, just you're much more
> likely to hit it.

Also if using a 64bit time_t means less compat gunge it makes things much
easier. At that point 32bit time_t becomes a userspace/library thunking
problen.

> IMHO the only excuse right now for 32bit is to use it in a JIT
> that can dynamically expand the pointer. Or for old binaries.

Or for a lot of code which runs way faster in 32bit pointer mode. Less
memory, smaller cache footprint.

Alan
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