From: Marc Zyngier <marc.zyngier@arm.com>
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Christopher Covington <cov@codeaurora.org>,
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>,
"konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
Catalin Marinas <Catalin.Marinas@arm.com>,
Will Deacon <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: Fri, 03 May 2013 11:54:34 +0100 [thread overview]
Message-ID: <5183976A.6000703@arm.com> (raw)
In-Reply-To: <alpine.DEB.2.02.1305031130210.5398@kaball.uk.xensource.com>
On 03/05/13 11:43, Stefano Stabellini wrote:
> On Thu, 2 May 2013, Christopher Covington wrote:
>>> So the virtual timer should appear to have been running even while time
>>> is being stolen and therefore stolen time needs to be accounted via some
>>> other means.
>>
>> Something that's not currently obvious to me is that given that the stolen
>> cycle accounting should be done, what makes the architected timer interrupt
>> handler the ideal place to do it?
>
> That is a good question and I would appreciate suggestions to improve
> the patch.
>
> Given that Xen x86 and ia64 does stolen time accounting from the timer
> interrupt handler:
>
> arch/x86/xen/time.c:xen_timer_interrupt
> arch/ia64/kernel/time.c:timer_interrupt
>
> and given that the arch_timer is the only timer used by Xen on ARM and
> that it includes a virt_timer that is made on purpose to be used by
> virtual machines, I thought that it might be a good place for it.
>
> I also thought that doing it this way, KVM should be able to reuse the
> same hook.
Indeed. I just need to understand how time stealing works there ;-).
Now, KVM is not necessarily limited to arch_timers, and we've run KVM
using a QEMU-provided timer in the past. Can you think of a more generic
location for this hook? Possibly something that would satisfy the
requirements of other architectures while we're at it?
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2013-05-03 10:54 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 [this message]
2013-05-05 16:47 ` Stefano Stabellini
2013-05-06 14:55 ` Christopher Covington
2013-05-06 14:35 ` Konrad Rzeszutek Wilk
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5183976A.6000703@arm.com \
--to=marc.zyngier@arm.com \
--cc=Catalin.Marinas@arm.com \
--cc=Ian.Campbell@citrix.com \
--cc=Will.Deacon@arm.com \
--cc=cov@codeaurora.org \
--cc=john.stultz@linaro.org \
--cc=konrad.wilk@oracle.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@arm.linux.org.uk \
--cc=stefano.stabellini@eu.citrix.com \
--cc=xen-devel@lists.xensource.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).