linux-kernel - Re: 2.6.32-rc3: low mem - only 378MB on x86

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 10 Oct 2009 14:10:36 -0400
From:	Valdis.Kletnieks@...edu
To:	Jeff Chua <jeff.chua.linux@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Tomasz Chmielewski <mangoo@...g.org>,
	Daniel J Blueman <daniel.blueman@...il.com>,
	Byron Stanoszek <bstanoszek@...time.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: 2.6.32-rc3: low mem - only 378MB on x86_32 with 64GB. Why?

On Sat, 10 Oct 2009 00:28:42 +0800, Jeff Chua said:

> From all the reading I've read about how slow 64-bit was, after doing all
> the lean and mean compiling, 64-bit is definitely the way to go! Fast and
> worth every bit switching to 64-bit! Now I can go for 128GB ram.

When the MIPS, PowerPC, and Sparc architectures went from 32 to 64 bits,
they *did* take a bit of a performance hit because it basically doubled
the memory bandwidth usage.  However, they all had a reasonably large
number of registers in 32-bit mode.  When the x86 went 64-bit, the register
pressure relief from the additional registers usually more then outweighs
the additional memory bandwidth (basically, if you're spending twice as
much time on each load/store, but only doing it 40% as often, you come out
ahead...)

Content of type "application/pgp-signature" skipped