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[Xen-devel] Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable
- To: Andi Kleen <ak@xxxxxx>
- From: Zachary Amsden <zach@xxxxxxxxxx>
- Date: Tue, 20 Mar 2007 11:54:25 -0800
- Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, akpm@xxxxxxxxxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, chrisw@xxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxx, "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>, anthony@xxxxxxxxxxxxx, mingo@xxxxxxx, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, David Miller <davem@xxxxxxxxxxxxx>
- Delivery-date: Tue, 20 Mar 2007 13:39:18 -0700
- List-id: Xen developer discussion <xen-devel.lists.xensource.com>
Andi Kleen wrote:
One thing I was pondering was to replace the expensive popfs with
bt $IF,(%rsp)
jnc 1f
sti
1:
But would be mostly a P4 optimization again and I'm not 100% sure it is
worth it.
Worth it on 32-bit. On AMD64, probably not. On Intel 64-bit, maybe,
but less important than in P4 days.
This could change character completely if used at the tail of a function
where you now have
sti; 1: ret
Which generates an interrupt holdoff on the ret, an unusual thing to do.
Zach
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