From: Julien Grall <julien.grall@arm.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: Vijay Kilari <vijay.kilari@gmail.com>,
Steve Capper <Steve.Capper@arm.com>,
Andre Przywara <andre.przywara@arm.com>,
Dario Faggioli <dario.faggioli@citrix.com>,
george.dunlap@citrix.com,
xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [RFC PATCH 21/24] ARM: vITS: handle INVALL command
Date: Tue, 6 Dec 2016 23:13:32 +0000 [thread overview]
Message-ID: <dae9a4d7-6333-b56f-db6c-688ef9a6c60c@arm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1612061356000.6598@sstabellini-ThinkPad-X260>
Hi Stefano,
On 06/12/2016 22:01, Stefano Stabellini wrote:
> On Tue, 6 Dec 2016, Stefano Stabellini wrote:
>> moving a vCPU with interrupts assigned to it is slower than moving a
>> vCPU without interrupts assigned to it. You could say that the
>> slowness is directly proportional do the number of interrupts assigned
>> to the vCPU.
>
> To be pedantic, by "assigned" I mean that a physical interrupt is routed
> to a given pCPU and is set to be forwarded to a guest vCPU running on it
> by the _IRQ_GUEST flag. The guest could be dom0. Upon receiving one of
> these physical interrupts, a corresponding virtual interrupt (could be a
> different irq) will be injected into the guest vCPU.
>
> When the vCPU is migrated to a new pCPU, the physical interrupts that
> are configured to be injected as virtual interrupts into the vCPU, are
> migrated with it. The physical interrupt migration has a cost. However,
> receiving physical interrupts on the wrong pCPU has an higher cost.
I don't understand why it is a problem for you to receive the first
interrupt to the wrong pCPU and moving it if necessary.
While this may have an higher cost (I don't believe so) on the first
received interrupt, migrating thousands of interrupts at the same time
is very expensive and will likely get Xen stuck for a while (think about
ITS with a single command queue).
Furthermore, the current approach will move every single interrupt
routed a the vCPU, even those disabled. That's pointless and a waste of
resource. You may argue that we can skip the ones disabled, but in that
case what would be the benefits to migrate the IRQs while migrate the vCPUs?
So I would suggest to spread it over the time. This also means less
headache for the scheduler developers.
Regards,
--
Julien Grall
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next prev parent reply other threads:[~2016-12-06 23:13 UTC|newest]
Thread overview: 144+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-28 18:24 [RFC PATCH 00/24] [FOR 4.9] arm64: Dom0 ITS emulation Andre Przywara
2016-09-28 18:24 ` [RFC PATCH 01/24] ARM: GICv3 ITS: parse and store ITS subnodes from hardware DT Andre Przywara
2016-10-26 1:11 ` Stefano Stabellini
2016-11-01 15:13 ` Julien Grall
2016-11-14 17:35 ` Andre Przywara
2016-11-23 15:39 ` Julien Grall
2016-09-28 18:24 ` [RFC PATCH 02/24] ARM: GICv3: allocate LPI pending and property table Andre Przywara
2016-10-24 14:28 ` Vijay Kilari
2016-11-02 16:22 ` Andre Przywara
2016-10-26 1:10 ` Stefano Stabellini
2016-11-10 15:29 ` Andre Przywara
2016-11-10 21:00 ` Stefano Stabellini
2016-11-01 17:22 ` Julien Grall
2016-11-15 11:32 ` Andre Przywara
2016-11-23 15:58 ` Julien Grall
2016-09-28 18:24 ` [RFC PATCH 03/24] ARM: GICv3 ITS: allocate device and collection table Andre Przywara
2016-10-09 13:55 ` Vijay Kilari
2016-10-10 9:05 ` Andre Przywara
2016-10-24 14:30 ` Vijay Kilari
2016-11-02 17:51 ` Andre Przywara
2016-10-26 22:57 ` Stefano Stabellini
2016-11-01 17:34 ` Julien Grall
2016-11-10 15:32 ` Andre Przywara
2016-11-10 21:06 ` Stefano Stabellini
2016-11-01 18:19 ` Julien Grall
2016-09-28 18:24 ` [RFC PATCH 04/24] ARM: GICv3 ITS: map ITS command buffer Andre Przywara
2016-10-24 14:31 ` Vijay Kilari
2016-10-26 23:03 ` Stefano Stabellini
2016-11-10 16:04 ` Andre Przywara
2016-11-02 13:38 ` Julien Grall
2016-09-28 18:24 ` [RFC PATCH 05/24] ARM: GICv3 ITS: introduce ITS command handling Andre Przywara
2016-10-26 23:55 ` Stefano Stabellini
2016-10-27 21:52 ` Stefano Stabellini
2016-11-10 15:57 ` Andre Przywara
2016-11-02 15:05 ` Julien Grall
2017-01-31 9:10 ` Andre Przywara
2017-01-31 10:23 ` Julien Grall
2016-09-28 18:24 ` [RFC PATCH 06/24] ARM: GICv3 ITS: introduce host LPI array Andre Przywara
2016-10-27 22:59 ` Stefano Stabellini
2016-11-02 15:14 ` Julien Grall
2016-11-10 17:22 ` Andre Przywara
2016-11-10 21:48 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 07/24] ARM: GICv3 ITS: introduce device mapping Andre Przywara
2016-10-24 15:31 ` Vijay Kilari
2016-11-03 19:33 ` Andre Przywara
2016-10-28 0:08 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 08/24] ARM: GICv3: introduce separate pending_irq structs for LPIs Andre Przywara
2016-10-24 15:31 ` Vijay Kilari
2016-11-03 19:47 ` Andre Przywara
2016-10-28 1:04 ` Stefano Stabellini
2017-01-12 19:14 ` Andre Przywara
2017-01-13 19:37 ` Stefano Stabellini
2017-01-16 9:44 ` André Przywara
2017-01-16 19:16 ` Stefano Stabellini
2016-11-04 15:46 ` Julien Grall
2016-09-28 18:24 ` [RFC PATCH 09/24] ARM: GICv3: forward pending LPIs to guests Andre Przywara
2016-10-28 1:51 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 10/24] ARM: GICv3: enable ITS and LPIs on the host Andre Przywara
2016-10-28 23:07 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 11/24] ARM: vGICv3: handle virtual LPI pending and property tables Andre Przywara
2016-10-24 15:32 ` Vijay Kilari
2016-11-03 20:21 ` Andre Przywara
2016-11-04 11:53 ` Julien Grall
2016-10-29 0:39 ` Stefano Stabellini
2017-03-29 15:47 ` Andre Przywara
2016-11-02 17:18 ` Julien Grall
2016-11-02 17:41 ` Stefano Stabellini
2016-11-02 18:03 ` Julien Grall
2016-11-02 18:09 ` Stefano Stabellini
2017-01-31 9:10 ` Andre Przywara
2017-01-31 10:38 ` Julien Grall
2017-01-31 12:04 ` Andre Przywara
2016-09-28 18:24 ` [RFC PATCH 12/24] ARM: vGICv3: introduce basic ITS emulation bits Andre Przywara
2016-10-09 14:20 ` Vijay Kilari
2016-10-10 10:38 ` Andre Przywara
2016-10-24 15:31 ` Vijay Kilari
2016-11-03 19:26 ` Andre Przywara
2016-11-04 12:07 ` Julien Grall
2016-11-03 17:50 ` Julien Grall
2016-11-08 23:54 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 13/24] ARM: vITS: handle CLEAR command Andre Przywara
2016-11-04 15:48 ` Julien Grall
2016-11-09 0:39 ` Stefano Stabellini
2016-11-09 13:32 ` Julien Grall
2016-09-28 18:24 ` [RFC PATCH 14/24] ARM: vITS: handle INT command Andre Przywara
2016-11-09 0:42 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 15/24] ARM: vITS: handle MAPC command Andre Przywara
2016-11-09 0:48 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 16/24] ARM: vITS: handle MAPD command Andre Przywara
2016-11-09 0:54 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 17/24] ARM: vITS: handle MAPTI command Andre Przywara
2016-11-09 1:07 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 18/24] ARM: vITS: handle MOVI command Andre Przywara
2016-11-09 1:13 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 19/24] ARM: vITS: handle DISCARD command Andre Przywara
2016-11-09 1:28 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 20/24] ARM: vITS: handle INV command Andre Przywara
2016-11-09 1:49 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 21/24] ARM: vITS: handle INVALL command Andre Przywara
2016-10-24 15:32 ` Vijay Kilari
2016-11-04 9:22 ` Andre Przywara
2016-11-10 0:21 ` Stefano Stabellini
2016-11-10 11:57 ` Julien Grall
2016-11-10 20:42 ` Stefano Stabellini
2016-11-11 15:53 ` Julien Grall
2016-11-11 20:31 ` Stefano Stabellini
2016-11-18 18:39 ` Stefano Stabellini
2016-11-25 16:10 ` Julien Grall
2016-12-01 1:19 ` Stefano Stabellini
2016-12-02 16:18 ` Andre Przywara
2016-12-03 0:46 ` Stefano Stabellini
2016-12-05 13:36 ` Julien Grall
2016-12-05 19:51 ` Stefano Stabellini
2016-12-06 15:56 ` Julien Grall
2016-12-06 19:36 ` Stefano Stabellini
2016-12-06 21:32 ` Dario Faggioli
2016-12-06 21:53 ` Stefano Stabellini
2016-12-06 22:01 ` Stefano Stabellini
2016-12-06 22:12 ` Dario Faggioli
2016-12-06 23:13 ` Julien Grall [this message]
2016-12-07 20:20 ` Stefano Stabellini
2016-12-09 18:01 ` Julien Grall
2016-12-09 20:13 ` Stefano Stabellini
2016-12-09 18:07 ` Andre Przywara
2016-12-09 20:18 ` Stefano Stabellini
2016-12-14 2:39 ` George Dunlap
2016-12-16 1:30 ` Dario Faggioli
2016-12-06 22:39 ` Dario Faggioli
2016-12-06 23:24 ` Julien Grall
2016-12-07 0:17 ` Dario Faggioli
2016-12-07 20:21 ` Stefano Stabellini
2016-12-09 10:14 ` Dario Faggioli
2016-12-06 21:36 ` Dario Faggioli
2016-12-09 19:00 ` Andre Przywara
2016-12-10 0:30 ` Stefano Stabellini
2016-12-12 10:38 ` Andre Przywara
2016-12-14 0:38 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 22/24] ARM: vITS: create and initialize virtual ITSes for Dom0 Andre Przywara
2016-11-10 0:38 ` Stefano Stabellini
2016-09-28 18:24 ` [RFC PATCH 23/24] ARM: vITS: create ITS subnodes for Dom0 DT Andre Przywara
2016-09-28 18:24 ` [RFC PATCH 24/24] ARM: vGIC: advertising LPI support Andre Przywara
2016-11-10 0:49 ` Stefano Stabellini
2016-11-10 11:22 ` Julien Grall
2016-11-02 13:56 ` [RFC PATCH 00/24] [FOR 4.9] arm64: Dom0 ITS emulation Julien Grall
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