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Date: Mon, 10 Mar 2003 11:14:39 -0800 (PST)
Message-Id: <20030310.111439.130618014.davem@redhat.com>
To: torvalds@transmeta.com
Cc: linux-kernel@vger.kernel.org
Subject: Re: [BK-2.5] Move "used FPU status" into new non-atomic
 thread_info->status field.
From: "David S. Miller" <davem@redhat.com>
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   From: Linus Torvalds <torvalds@transmeta.com>
   Date: Mon, 10 Mar 2003 11:25:55 -0800 (PST)
   
   > Are you preserving FPU state across fork() on x86?  If so, what do you
   > think might rely on this?
   
   Probably nothing per se. HOWEVER, we'd still need to save the state for 
   rounding etc, so we might as well save it all.
   
I see.

We preserve the rounding/etc. modes on sparc, we merely zap the actual
FPU registers around the system call.

And that's like 4 L2 cache lines of registers on sparc64, so there
really is a benefit from only saving the mode register across a system
call.