linux-kernel - Re: Word-at-a-time dcache name accesses (was Re: .. anybody know of any filesystems that depend on the exact VFS 'namehash' implementation?)

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Message-ID: <20120304221915.GA19570@parisc-linux.org>
Date:	Sun, 4 Mar 2012 15:19:16 -0700
From:	Matthew Wilcox <matthew@....cx>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	david@...g.hm, Ted Ts'o <tytso@....edu>,
	Andi Kleen <andi@...stfloor.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: Word-at-a-time dcache name accesses (was Re: .. anybody know
	of any filesystems that depend on the exact VFS 'namehash'
	implementation?)

On Fri, Mar 02, 2012 at 04:24:11PM -0800, Linus Torvalds wrote:
> Tons of CPU's have efficient char accesses but horrible unaligned word
> accesses. Some are even outright buggy (ie at least some ARM cores)
> and load crap. Others take a fault.

To be fair, that wasn't the ARM core.  That was the MEMC chip (roughly
equivalent to a northbridge).  Also, there's no need for Linux to care
about that any more, since we removed the arm26 port in July 2007.  As far
as I know, all arm32 cores have been coupled with memory controllers
that are functional.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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