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From: Andi Kleen <ak@suse.de>
To: rohitseth@google.com
Subject: Re: [RFC, patch] i386: vgetcpu(), take 2
Date: Thu, 22 Jun 2006 00:21:21 +0200
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> Can we use similar  mechanism to access pda in vsyscall in x86_64 (by
> storing the address of pda there).  


You mean in the kernel? %gs prefix is a lot faster than this.

Also the limit is only 20bit, not enough for a full address.

For user space it's useful though, but I don't see any immediate uses
other than cpu number and node number. For most purposes glibc TLS
(which uses %fs) is probably sufficient.

-Andi