Re: [PATCH 1/2] x86/entry: Avoid interrupt flag save and restore

From: Rik van Riel
Date: Wed Jun 01 2016 - 10:52:41 EST

On Mon, 2016-05-30 at 14:30 +0200, Paolo Bonzini wrote:
> Thanks to all the work that was done by Andy Lutomirski and others,
> enter_from_user_mode and prepare_exit_to_usermode are now called only
> with
> interrupts disabled.ÂÂLet's provide them a version of
> user_enter/user_exit
> that skips saving and restoring the interrupt flag.
> On an AMD-based machine I tested this patch on, with force-enabled
> context tracking, the speed-up in system calls was 90 clock cycles or
> 6%,
> measured with the following simple benchmark:

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

All Rights Reversed.

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