From: Andi Kleen <andi@firstfloor.org>
To: Avi Kivity <avi@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>, Ingo Molnar <mingo@elte.hu>,
x86@kernel.org, linux-kernel <linux-kernel@vger.kernel.org>,
KVM list <kvm@vger.kernel.org>
Subject: Re: [PATCH 0/3] Remove interrupt stack table usage from x86_64 kernel
Date: Sun, 28 Dec 2008 21:34:25 +0100 [thread overview]
Message-ID: <20081228203425.GF496@one.firstfloor.org> (raw)
In-Reply-To: <4957DCC3.3060505@redhat.com>
On Sun, Dec 28, 2008 at 10:08:35PM +0200, Avi Kivity wrote:
> Avi Kivity wrote:
> >Avi Kivity wrote:
> >>1. Add per-cpu IDT
> >
> >Or we could have just two IDTs - one with IST and one without. I
> >clocked LIDT at 58 cycles (and we need two per heavyweight switch), so
> >it's not that wonderful.
>
> This makes the whole thing unworthwhile. The vmload/vmsave pair costs
> only 200 cycles (I should have started with this), and 120 cycles on the
> heavyweight path plus complexity are not worth 200 cycles on the
> lightweight path.
Actually to switch ISTs you need to change the TSS, not the IDT.
But I suppose that won't be any faster.
-Andi
--
ak@linux.intel.com
next prev parent reply other threads:[~2008-12-28 20:21 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-25 20:58 [PATCH 0/3] Remove interrupt stack table usage from x86_64 kernel Avi Kivity
2008-12-25 20:58 ` [PATCH 1/3] x86: drop the use of the tss interrupt stack table (IST) Avi Kivity
2008-12-25 20:58 ` [PATCH 2/3] x86: Remove pda.irqcount Avi Kivity
2008-12-25 20:58 ` [PATCH 3/3] x86: Switch critical exceptions and NMI to irqstack Avi Kivity
2008-12-26 9:15 ` [PATCH 0/3] Remove interrupt stack table usage from x86_64 kernel Ingo Molnar
[not found] ` <87vdt5vfxc.fsf@basil.nowhere.org>
[not found] ` <4956A0B1.1060908@redhat.com>
[not found] ` <20081227224029.GB496@one.firstfloor.org>
[not found] ` <49573FE7.9090802@redhat.com>
[not found] ` <20081228131605.GC496@one.firstfloor.org>
2008-12-28 14:09 ` Avi Kivity
2008-12-28 19:08 ` Andi Kleen
2008-12-28 19:07 ` Avi Kivity
2008-12-28 19:19 ` Avi Kivity
2008-12-28 20:08 ` Avi Kivity
2008-12-28 20:34 ` Andi Kleen [this message]
2008-12-28 20:28 ` Avi Kivity
2008-12-28 19:30 ` Andi Kleen
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