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[Xen-devel] [PATCH 0/2, v2] x86: adjust entry frame generation

  • To: "xen-devel" <xen-devel@xxxxxxxxxxxxx>
  • From: "Jan Beulich" <JBeulich@xxxxxxxx>
  • Date: Tue, 30 Oct 2012 14:20:23 +0000
  • Delivery-date: Tue, 30 Oct 2012 14:20:12 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>

>>> On 02.10.12 at 17:20, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
This pair of patches converts the way frames gets created from
using PUSHes/POPs to using MOVes, thus allowing (in certain
cases) to avoid saving/restoring part of the register set.

While the exact place where the (small) win from this comes from
varies between CPUs, the net effect is a 1 to 2% reduction on a
combined interruption entry and exit when the full state save
can be avoided.

1: use MOV instead of PUSH/POP when saving/restoring register state
2: save only partial register state where possible

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
NB: Patch 1 didn't change from its v1 submission, and what was
originally patch 2 (of 3) did already get committed.

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