From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>,
Wei Liu <wei.liu2@citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH 2/9] x86/IRQ: deal with move cleanup count state in fixup_irqs()
Date: Fri, 3 May 2019 17:21:42 +0200 [thread overview]
Message-ID: <20190503152142.icdzlax4arik3beg@Air-de-Roger> (raw)
In-Reply-To: <5CC6DEA80200007800229E9D@prv1-mh.provo.novell.com>
On Mon, Apr 29, 2019 at 05:23:20AM -0600, Jan Beulich wrote:
> The cleanup IPI may get sent immediately before a CPU gets removed from
> the online map. In such a case the IPI would get handled on the CPU
> being offlined no earlier than in the interrupts disabled window after
> fixup_irqs()' main loop. This is too late, however, because a possible
> affinity change may incur the need for vector assignment, which will
> fail when the IRQ's move cleanup count is still non-zero.
>
> To fix this
> - record the set of CPUs the cleanup IPIs gets actually sent to alongside
> setting their count,
> - adjust the count in fixup_irqs(), accounting for all CPUs that the
> cleanup IPI was sent to, but that are no longer online,
> - bail early from the cleanup IPI handler when the CPU is no longer
> online, to prevent double accounting.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Just as a note, this whole interrupt migration business seems
extremely complex, and I wonder if Xen does really need it, or what's
exactly it's performance gain compared to more simple solutions. I
understand this is just fixes, but IMO it's making the logic even more
complex.
Maybe it would be simpler to have the interrupts hard-bound to pCPUs
and instead have a soft-affinity on the guest vCPUs that are assigned
as the destination?
> ---
> TBD: The proper recording of the IPI destinations actually makes the
> move_cleanup_count field redundant. Do we want to drop it, at the
> price of a few more CPU-mask operations?
AFAICT this is not a hot path, so I would remove the
move_cleanup_count field and just weight the cpu bitmap when needed.
Thanks, Roger.
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Xen-devel@lists.xenproject.org
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WARNING: multiple messages have this Message-ID (diff)
From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>,
Wei Liu <wei.liu2@citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [Xen-devel] [PATCH 2/9] x86/IRQ: deal with move cleanup count state in fixup_irqs()
Date: Fri, 3 May 2019 17:21:42 +0200 [thread overview]
Message-ID: <20190503152142.icdzlax4arik3beg@Air-de-Roger> (raw)
Message-ID: <20190503152142.hhNtkEqqacuyQ-edo11bInm_tOoiwYqwX-NsDQW0oKo@z> (raw)
In-Reply-To: <5CC6DEA80200007800229E9D@prv1-mh.provo.novell.com>
On Mon, Apr 29, 2019 at 05:23:20AM -0600, Jan Beulich wrote:
> The cleanup IPI may get sent immediately before a CPU gets removed from
> the online map. In such a case the IPI would get handled on the CPU
> being offlined no earlier than in the interrupts disabled window after
> fixup_irqs()' main loop. This is too late, however, because a possible
> affinity change may incur the need for vector assignment, which will
> fail when the IRQ's move cleanup count is still non-zero.
>
> To fix this
> - record the set of CPUs the cleanup IPIs gets actually sent to alongside
> setting their count,
> - adjust the count in fixup_irqs(), accounting for all CPUs that the
> cleanup IPI was sent to, but that are no longer online,
> - bail early from the cleanup IPI handler when the CPU is no longer
> online, to prevent double accounting.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Just as a note, this whole interrupt migration business seems
extremely complex, and I wonder if Xen does really need it, or what's
exactly it's performance gain compared to more simple solutions. I
understand this is just fixes, but IMO it's making the logic even more
complex.
Maybe it would be simpler to have the interrupts hard-bound to pCPUs
and instead have a soft-affinity on the guest vCPUs that are assigned
as the destination?
> ---
> TBD: The proper recording of the IPI destinations actually makes the
> move_cleanup_count field redundant. Do we want to drop it, at the
> price of a few more CPU-mask operations?
AFAICT this is not a hot path, so I would remove the
move_cleanup_count field and just weight the cpu bitmap when needed.
Thanks, Roger.
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
next prev parent reply other threads:[~2019-05-03 15:22 UTC|newest]
Thread overview: 196+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-29 11:16 [PATCH 0/9] x86: IRQ management adjustments Jan Beulich
2019-04-29 11:16 ` [Xen-devel] " Jan Beulich
2019-04-29 11:22 ` [PATCH RFC 1/9] x86/IRQ: deal with move-in-progress state in fixup_irqs() Jan Beulich
2019-04-29 11:22 ` [Xen-devel] " Jan Beulich
2019-04-29 12:55 ` Jan Beulich
2019-04-29 12:55 ` [Xen-devel] " Jan Beulich
2019-04-29 13:08 ` Jan Beulich
2019-04-29 13:08 ` [Xen-devel] " Jan Beulich
2019-04-29 11:23 ` [PATCH 2/9] x86/IRQ: deal with move cleanup count " Jan Beulich
2019-04-29 11:23 ` [Xen-devel] " Jan Beulich
2019-05-03 15:21 ` Roger Pau Monné [this message]
2019-05-03 15:21 ` Roger Pau Monné
2019-05-06 7:44 ` Jan Beulich
2019-05-06 7:44 ` [Xen-devel] " Jan Beulich
2019-05-07 7:28 ` Jan Beulich
2019-05-07 7:28 ` [Xen-devel] " Jan Beulich
2019-05-07 8:12 ` Roger Pau Monné
2019-05-07 8:12 ` [Xen-devel] " Roger Pau Monné
2019-05-07 9:28 ` Jan Beulich
2019-05-07 9:28 ` [Xen-devel] " Jan Beulich
2019-04-29 11:23 ` [PATCH 3/9] x86/IRQ: improve dump_irqs() Jan Beulich
2019-04-29 11:23 ` [Xen-devel] " Jan Beulich
2019-05-03 15:43 ` Roger Pau Monné
2019-05-03 15:43 ` [Xen-devel] " Roger Pau Monné
2019-05-06 8:06 ` Jan Beulich
2019-05-06 8:06 ` [Xen-devel] " Jan Beulich
2019-04-29 11:24 ` [PATCH 4/9] x86/IRQ: desc->affinity should strictly represent the requested value Jan Beulich
2019-04-29 11:24 ` [Xen-devel] " Jan Beulich
2019-05-03 16:21 ` Roger Pau Monné
2019-05-03 16:21 ` [Xen-devel] " Roger Pau Monné
2019-05-06 8:14 ` Jan Beulich
2019-05-06 8:14 ` [Xen-devel] " Jan Beulich
2019-04-29 11:25 ` [PATCH 5/9] x86/IRQ: fix locking around vector management Jan Beulich
2019-04-29 11:25 ` [Xen-devel] " Jan Beulich
2019-05-06 11:48 ` Roger Pau Monné
2019-05-06 11:48 ` [Xen-devel] " Roger Pau Monné
2019-05-06 13:06 ` Jan Beulich
2019-05-06 13:06 ` [Xen-devel] " Jan Beulich
2019-04-29 11:25 ` [PATCH 6/9] x86/IRQ: reduce unused space in struct arch_irq_desc Jan Beulich
2019-04-29 11:25 ` [Xen-devel] " Jan Beulich
2019-04-29 11:46 ` Andrew Cooper
2019-04-29 11:46 ` [Xen-devel] " Andrew Cooper
2019-04-29 11:26 ` [PATCH 7/9] x86/IRQ: drop redundant cpumask_empty() from move_masked_irq() Jan Beulich
2019-04-29 11:26 ` [Xen-devel] " Jan Beulich
2019-05-06 13:39 ` Roger Pau Monné
2019-05-06 13:39 ` [Xen-devel] " Roger Pau Monné
2019-04-29 11:26 ` [PATCH 8/9] x86/IRQ: make fixup_irqs() skip unconnected internally used interrupts Jan Beulich
2019-04-29 11:26 ` [Xen-devel] " Jan Beulich
2019-05-06 13:52 ` Roger Pau Monné
2019-05-06 13:52 ` [Xen-devel] " Roger Pau Monné
2019-05-06 14:25 ` Jan Beulich
2019-05-06 14:25 ` [Xen-devel] " Jan Beulich
2019-05-06 14:37 ` Roger Pau Monné
2019-05-06 14:37 ` [Xen-devel] " Roger Pau Monné
2019-04-29 11:27 ` [PATCH 9/9] x86/IO-APIC: drop an unused variable from setup_IO_APIC_irqs() Jan Beulich
2019-04-29 11:27 ` [Xen-devel] " Jan Beulich
2019-04-29 11:40 ` Andrew Cooper
2019-04-29 11:40 ` [Xen-devel] " Andrew Cooper
2019-04-29 15:40 ` [PATCH v1b 1/9] x86/IRQ: deal with move-in-progress state in fixup_irqs() Jan Beulich
2019-04-29 15:40 ` [Xen-devel] " Jan Beulich
2019-05-03 9:19 ` Roger Pau Monné
2019-05-03 9:19 ` [Xen-devel] " Roger Pau Monné
2019-05-03 14:10 ` Jan Beulich
2019-05-03 14:10 ` [Xen-devel] " Jan Beulich
2019-05-06 7:15 ` Jan Beulich
2019-05-06 7:15 ` [Xen-devel] " Jan Beulich
2019-05-06 14:28 ` Roger Pau Monné
2019-05-06 14:28 ` [Xen-devel] " Roger Pau Monné
2019-05-06 15:00 ` Jan Beulich
2019-05-06 15:00 ` [Xen-devel] " Jan Beulich
2019-05-08 12:59 ` [PATCH v2 00/12] x86: IRQ management adjustments Jan Beulich
2019-05-08 12:59 ` [Xen-devel] " Jan Beulich
2019-05-08 13:03 ` [PATCH v2 01/12] x86/IRQ: deal with move-in-progress state in fixup_irqs() Jan Beulich
2019-05-08 13:03 ` [Xen-devel] " Jan Beulich
2019-05-13 9:04 ` Roger Pau Monné
2019-05-13 9:04 ` [Xen-devel] " Roger Pau Monné
2019-05-13 9:09 ` Jan Beulich
2019-05-13 9:09 ` [Xen-devel] " Jan Beulich
2019-05-08 13:03 ` [PATCH v2 02/12] x86/IRQ: deal with move cleanup count " Jan Beulich
2019-05-08 13:03 ` [Xen-devel] " Jan Beulich
2019-05-08 13:07 ` [PATCH v2 03/12] x86/IRQ: avoid UB (or worse) in trace_irq_mask() Jan Beulich
2019-05-08 13:07 ` [Xen-devel] " Jan Beulich
2019-05-13 9:08 ` Roger Pau Monné
2019-05-13 9:08 ` [Xen-devel] " Roger Pau Monné
2019-05-13 10:42 ` George Dunlap
2019-05-13 10:42 ` [Xen-devel] " George Dunlap
2019-05-13 12:05 ` Jan Beulich
2019-05-13 12:05 ` [Xen-devel] " Jan Beulich
2019-05-08 13:08 ` [PATCH v2 04/12] x86/IRQ: improve dump_irqs() Jan Beulich
2019-05-08 13:08 ` [Xen-devel] " Jan Beulich
2019-05-08 13:09 ` [PATCH v2 05/12] x86/IRQ: desc->affinity should strictly represent the requested value Jan Beulich
2019-05-08 13:09 ` [Xen-devel] " Jan Beulich
2019-05-08 13:10 ` [PATCH v2 06/12] x86/IRQ: consolidate use of ->arch.cpu_mask Jan Beulich
2019-05-08 13:10 ` [Xen-devel] " Jan Beulich
2019-05-13 11:32 ` Roger Pau Monné
2019-05-13 11:32 ` [Xen-devel] " Roger Pau Monné
2019-05-13 15:21 ` Jan Beulich
2019-05-13 15:21 ` [Xen-devel] " Jan Beulich
2019-05-08 13:10 ` [PATCH v2 07/12] x86/IRQ: fix locking around vector management Jan Beulich
2019-05-08 13:10 ` [Xen-devel] " Jan Beulich
2019-05-08 13:16 ` Jan Beulich
2019-05-08 13:16 ` [Xen-devel] " Jan Beulich
2019-05-11 0:11 ` Tian, Kevin
2019-05-11 0:11 ` [Xen-devel] " Tian, Kevin
2019-05-13 13:48 ` Roger Pau Monné
2019-05-13 13:48 ` [Xen-devel] " Roger Pau Monné
2019-05-13 14:19 ` Jan Beulich
2019-05-13 14:19 ` [Xen-devel] " Jan Beulich
2019-05-13 14:45 ` Roger Pau Monné
2019-05-13 14:45 ` [Xen-devel] " Roger Pau Monné
2019-05-13 15:05 ` Jan Beulich
2019-05-13 15:05 ` [Xen-devel] " Jan Beulich
2019-05-08 13:11 ` [PATCH v2 08/12] x86/IRQs: correct/tighten vector check in _clear_irq_vector() Jan Beulich
2019-05-08 13:11 ` [Xen-devel] " Jan Beulich
2019-05-13 14:01 ` Roger Pau Monné
2019-05-13 14:01 ` [Xen-devel] " Roger Pau Monné
2019-05-08 13:12 ` [PATCH v2 09/12] x86/IRQ: make fixup_irqs() skip unconnected internally used interrupts Jan Beulich
2019-05-08 13:12 ` [Xen-devel] " Jan Beulich
2019-05-08 13:13 ` [PATCH v2 10/12] x86/IRQ: reduce unused space in struct arch_irq_desc Jan Beulich
2019-05-08 13:13 ` [Xen-devel] " Jan Beulich
2019-05-08 13:13 ` [PATCH v2 11/12] x86/IRQ: drop redundant cpumask_empty() from move_masked_irq() Jan Beulich
2019-05-08 13:13 ` [Xen-devel] " Jan Beulich
2019-05-08 13:14 ` [PATCH v2 12/12] x86/IRQ: simplify and rename pirq_acktype() Jan Beulich
2019-05-08 13:14 ` [Xen-devel] " Jan Beulich
2019-05-13 14:14 ` Roger Pau Monné
2019-05-13 14:14 ` [Xen-devel] " Roger Pau Monné
2019-05-17 10:39 ` [PATCH v3 00/15] x86: IRQ management adjustments Jan Beulich
2019-05-17 10:39 ` [Xen-devel] " Jan Beulich
2019-05-17 10:44 ` [PATCH v3 01/15] x86/IRQ: deal with move-in-progress state in fixup_irqs() Jan Beulich
2019-05-17 10:44 ` [Xen-devel] " Jan Beulich
2019-07-03 15:39 ` Andrew Cooper
2019-07-04 9:32 ` Jan Beulich
2019-05-17 10:45 ` [PATCH v3 02/15] x86/IRQ: deal with move cleanup count " Jan Beulich
2019-05-17 10:45 ` [Xen-devel] " Jan Beulich
2019-07-03 16:32 ` Andrew Cooper
2019-05-17 10:46 ` [PATCH v3 03/15] x86/IRQ: improve dump_irqs() Jan Beulich
2019-05-17 10:46 ` [Xen-devel] " Jan Beulich
2019-07-03 16:39 ` Andrew Cooper
2019-05-17 10:46 ` [PATCH v3 04/15] x86/IRQ: desc->affinity should strictly represent the requested value Jan Beulich
2019-05-17 10:46 ` [Xen-devel] " Jan Beulich
2019-07-03 17:58 ` Andrew Cooper
2019-07-04 9:37 ` Jan Beulich
2019-05-17 10:47 ` [PATCH v3 05/15] x86/IRQ: consolidate use of ->arch.cpu_mask Jan Beulich
2019-05-17 10:47 ` [Xen-devel] " Jan Beulich
2019-07-03 18:07 ` Andrew Cooper
2019-05-17 10:47 ` [PATCH v3 06/15] x86/IRQ: fix locking around vector management Jan Beulich
2019-05-17 10:47 ` [Xen-devel] " Jan Beulich
2019-07-03 18:23 ` Andrew Cooper
2019-07-04 9:54 ` Jan Beulich
2019-05-17 10:48 ` [PATCH v3 07/15] x86/IRQ: target online CPUs when binding guest IRQ Jan Beulich
2019-05-17 10:48 ` [Xen-devel] " Jan Beulich
2019-05-20 11:40 ` Roger Pau Monné
2019-05-20 11:40 ` [Xen-devel] " Roger Pau Monné
2019-05-20 15:17 ` Jan Beulich
2019-05-20 15:17 ` [Xen-devel] " Jan Beulich
2019-05-22 9:41 ` Roger Pau Monné
2019-05-22 9:41 ` [Xen-devel] " Roger Pau Monné
2019-07-03 18:30 ` Andrew Cooper
2019-05-17 10:49 ` [PATCH v3 08/15] x86/IRQs: correct/tighten vector check in _clear_irq_vector() Jan Beulich
2019-05-17 10:49 ` [Xen-devel] " Jan Beulich
2019-07-03 18:31 ` Andrew Cooper
2019-05-17 10:49 ` [PATCH v3 09/15] x86/IRQ: make fixup_irqs() skip unconnected internally used interrupts Jan Beulich
2019-05-17 10:49 ` [Xen-devel] " Jan Beulich
2019-07-03 18:36 ` Andrew Cooper
2019-05-17 10:50 ` [PATCH v3 10/15] x86/IRQ: drop redundant cpumask_empty() from move_masked_irq() Jan Beulich
2019-05-17 10:50 ` [Xen-devel] " Jan Beulich
2019-07-03 18:38 ` Andrew Cooper
2019-05-17 10:51 ` [PATCH v3 11/15] x86/IRQ: simplify and rename pirq_acktype() Jan Beulich
2019-05-17 10:51 ` [Xen-devel] " Jan Beulich
2019-07-03 18:39 ` Andrew Cooper
2019-05-17 10:51 ` [PATCH v3 12/15] x86/IRQ: add explicit tracing-enabled check to trace_irq_mask() Jan Beulich
2019-05-17 10:51 ` [Xen-devel] " Jan Beulich
2019-05-20 11:46 ` Roger Pau Monné
2019-05-20 11:46 ` [Xen-devel] " Roger Pau Monné
2019-07-03 18:41 ` Andrew Cooper
2019-07-04 10:01 ` Jan Beulich
2019-05-17 10:52 ` [PATCH v3 13/15] x86/IRQ: tighten vector checks Jan Beulich
2019-05-17 10:52 ` [Xen-devel] " Jan Beulich
2019-05-20 14:04 ` Roger Pau Monné
2019-05-20 14:04 ` [Xen-devel] " Roger Pau Monné
2019-05-20 15:26 ` Jan Beulich
2019-05-20 15:26 ` [Xen-devel] " Jan Beulich
2019-05-22 16:42 ` Roger Pau Monné
2019-05-22 16:42 ` [Xen-devel] " Roger Pau Monné
2019-05-23 8:36 ` Jan Beulich
2019-05-23 8:36 ` [Xen-devel] " Jan Beulich
2019-07-03 18:42 ` Andrew Cooper
2019-05-17 10:52 ` [PATCH v3 14/15] x86/IRQ: eliminate some on-stack cpumask_t instances Jan Beulich
2019-05-17 10:52 ` [Xen-devel] " Jan Beulich
2019-05-20 14:22 ` Roger Pau Monné
2019-05-20 14:22 ` [Xen-devel] " Roger Pau Monné
2019-07-03 18:44 ` Andrew Cooper
2019-07-04 10:04 ` Jan Beulich
2019-05-17 10:53 ` [PATCH v3 15/15] x86/IRQ: move {,_}clear_irq_vector() Jan Beulich
2019-05-17 10:53 ` [Xen-devel] " Jan Beulich
2019-07-03 18:45 ` [Xen-devel] [PATCH v3 15/15] x86/IRQ: move {, _}clear_irq_vector() Andrew Cooper
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