From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Christopher Covington <cov@codeaurora.org>
Cc: Ian Campbell <Ian.Campbell@citrix.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
"linux@arm.linux.org.uk" <linux@arm.linux.org.uk>,
"marc.zyngier@arm.com" <marc.zyngier@arm.com>,
"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>,
"will.deacon@arm.com" <will.deacon@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"john.stultz@linaro.org" <john.stultz@linaro.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [Xen-devel] [PATCH 1/3] arm_arch_timer: introduce arch_timer_stolen_ticks
Date: Mon, 6 May 2013 10:35:33 -0400 [thread overview]
Message-ID: <20130506143533.GF15278@phenom.dumpdata.com> (raw)
In-Reply-To: <5182DBA9.9080609@codeaurora.org>
> > e.g. if a VCPU sets a timer for NOW+5, but 3 are stolen in the middle it
> > would not make sense (from the guests PoV) for NOW'==NOW+2 at the point
> > where the timer goes off. Nor does it make sense to require that the
> > guest actually be running for 5 before injecting the timer because that
> > would mean real time elapsed time for the timer would be 5+3 in the case
> > where 3 are stolen.
>
> This is a bit of an aside, but I think that hiding time spent at higher
> privilege levels can be a quite sensible approach to timekeeping in a
> virtualized environment, but I understand that it's not the approach taken
> with Xen, and as you pointed out above, adjusting the Virtual Offset Register
> by itself isn't enough to implement that approach.
This is the approach taken by Xen and KVM. Look in CONFIG_PARAVIRT_CLOCK for
implementation. In the user-space, the entry in 'top' of "stolen" (%st)
is for this exact value.
next prev parent reply other threads:[~2013-05-06 14:36 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-01 19:27 [PATCH 0/3] xen/arm: account for stolen ticks Stefano Stabellini
2013-05-01 19:27 ` [PATCH 1/3] arm_arch_timer: introduce arch_timer_stolen_ticks Stefano Stabellini
2013-05-01 20:36 ` Christopher Covington
2013-05-02 8:19 ` [Xen-devel] " Ian Campbell
2013-05-02 21:33 ` Christopher Covington
2013-05-03 10:43 ` Stefano Stabellini
2013-05-03 10:54 ` Marc Zyngier
2013-05-05 16:47 ` Stefano Stabellini
2013-05-06 14:55 ` Christopher Covington
2013-05-06 14:35 ` Konrad Rzeszutek Wilk [this message]
2013-05-07 16:17 ` Christopher Covington
2013-05-08 11:19 ` Stefano Stabellini
2013-05-08 11:48 ` Christopher Covington
2013-05-01 19:27 ` [PATCH 2/3] xen: move do_stolen_accounting to drivers/xen/time.c Stefano Stabellini
2013-05-02 8:19 ` [Xen-devel] " Ian Campbell
2013-05-02 18:49 ` Christopher Covington
2013-05-03 8:26 ` [Xen-devel] " Ian Campbell
2013-05-03 10:29 ` Stefano Stabellini
2013-05-01 19:27 ` [PATCH 3/3] xen/arm: account for stolen ticks Stefano Stabellini
2013-05-02 8:21 ` [Xen-devel] " Ian Campbell
2013-05-02 10:38 ` Stefano Stabellini
2013-05-02 10:48 ` Ian Campbell
2013-05-02 10:54 ` Stefano Stabellini
2013-05-02 11:02 ` Ian Campbell
2013-05-02 11:04 ` Stefano Stabellini
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