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: <20120327050238.GA19496@redhat.com>
Date:	Tue, 27 Mar 2012 01:02:38 -0400
From:	Dave Jones <davej@...hat.com>
To:	Brian Gerst <brgerst@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jason Garrett-Glaser <jason@...4.com>,
	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 Tue, Mar 27, 2012 at 12:42:19AM -0400, Brian Gerst wrote:

 > > I did only very limited profiling of the 32-bit case, but it's really
 > > just four cheap ALU instructions there and didn't really show up at
 > > all in the limited profiles I did. And at least I checked that the
 > > code worked. I have to say that the advantage of "vectorizing" this
 > > code is obviously much less if you can only do 4-byte "vectors", so I
 > > didn't actually time whether the patch *improves* anything on x86-32.
 > >
 > 
 > This patch is causing my system (x86-64, Fedora 16) to fail to boot
 > when DEBUG_PAGEALLOC=n.  No oops, but these error messages were in the
 > log for the bad kernel:

I saw this too, it was fixed by f132c5be05e407a99cf582347a2ae0120acd3ad7 for me.
Does your kernel have that commit ?

	Dave


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