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From: Alexander Gordeev <agordeev@redhat.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
	Suresh Siddha <suresh.b.siddha@intel.com>,
	Cyrill Gorcunov <gorcunov@openvz.org>,
	Yinghai Lu <yinghai@kernel.org>
Subject: Re: [PATCH 2/3] x86: x2apic/cluster: Make use of lowest priority delivery mode
Date: Mon, 21 May 2012 11:36:49 +0200	[thread overview]
Message-ID: <20120521093648.GC28930@dhcp-26-207.brq.redhat.com> (raw)
In-Reply-To: <20120521082240.GA31407@gmail.com>

On Mon, May 21, 2012 at 10:22:40AM +0200, Ingo Molnar wrote:
> 
> * Alexander Gordeev <agordeev@redhat.com> wrote:
> 
> > Currently x2APIC in logical destination mode delivers 
> > interrupts to a single CPU, no matter how many CPUs were 
> > specified in the destination cpumask.
> > 
> > This fix enables delivery of interrupts to multiple CPUs by 
> > bit-ORing Logical IDs of destination CPUs that have matching 
> > Cluster ID.
> > 
> > Because only one cluster could be specified in a message 
> > destination address, the destination cpumask is tried for a 
> > cluster that contains maximum number of CPUs matching this 
> > cpumask. The CPUs in this cluster are selected to receive the 
> > interrupts while all other CPUs (in the cpumask) are ignored.
> 
> I'm wondering how you tested this. AFAICS current irqbalanced 
> will create masks but on x2apic only the first CPU is targeted 
> by the kernel.

Right, that is what this patch is intended to change. So I use:
'hwclock --test' to generate rtc interruts
/proc/interrupts to check where/how many interrupts were delevired
/proc/irq/8/smp_affinity to check how clusters are chosen

> So, in theory, prior the patch you should be seeing irqs go to 
> only one CPU, while after the patch they are spread out amongst 
> the CPU. If it's using LowestPrio delivery then we depend on the 
> hardware doing this for us - how does this work out in practice, 
> are the target CPUs round-robin-ed, with a new CPU for every new 
> IRQ delivered?


That is exactly what I can observe.

As of 'target CPUs round-robin-ed' and 'with a new CPU for every new IRQ
delivered' -- that is something we can not control as you noted. Nor do we
care to my understanding.

I can not commit on every h/w out there obviously, but on my PowerEdge M910
with some half-dozen clusters with six CPU per each, the interrupts are
perfectly balanced among those ones present in IRTEs.


> Thanks,
> 
> 	Ingo

-- 
Regards,
Alexander Gordeev
agordeev@redhat.com

  reply	other threads:[~2012-05-21  9:37 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-18 10:26 [PATCH 2/3] x86: x2apic/cluster: Make use of lowest priority delivery mode Alexander Gordeev
2012-05-18 14:41 ` Cyrill Gorcunov
2012-05-18 15:42   ` Alexander Gordeev
2012-05-18 15:51     ` Cyrill Gorcunov
2012-05-19 10:47       ` Cyrill Gorcunov
2012-05-21  7:11         ` Alexander Gordeev
2012-05-21  9:46           ` Cyrill Gorcunov
2012-05-19 20:53 ` Yinghai Lu
2012-05-21  8:13   ` Alexander Gordeev
2012-05-21 23:02     ` Yinghai Lu
2012-05-21 23:33       ` Yinghai Lu
2012-05-22  9:36         ` Alexander Gordeev
2012-05-21 23:44     ` Suresh Siddha
2012-05-21 23:58       ` [PATCH 1/2] x86, irq: update irq_cfg domain unless the new affinity is a subset of the current domain Suresh Siddha
2012-05-21 23:58         ` [PATCH 2/2] x2apic, cluster: use all the members of one cluster specified in the smp_affinity mask for the interrupt desintation Suresh Siddha
2012-05-22  7:04           ` Ingo Molnar
2012-05-22  7:34             ` Cyrill Gorcunov
2012-05-22 17:21             ` Suresh Siddha
2012-05-22 17:39               ` Cyrill Gorcunov
2012-05-22 17:42                 ` Suresh Siddha
2012-05-22 17:45                   ` Cyrill Gorcunov
2012-05-22 20:03           ` Yinghai Lu
2012-06-06 15:04           ` [tip:x86/apic] x86/x2apic/cluster: Use all the members of one cluster specified in the smp_affinity mask for the interrupt destination tip-bot for Suresh Siddha
2012-06-06 22:21             ` Yinghai Lu
2012-06-06 23:14               ` Suresh Siddha
2012-06-06 15:03         ` [tip:x86/apic] x86/irq: Update irq_cfg domain unless the new affinity is a subset of the current domain tip-bot for Suresh Siddha
2012-08-07 15:31           ` Robert Richter
2012-08-07 15:41             ` do_IRQ: 1.55 No irq handler for vector (irq -1) Borislav Petkov
2012-08-07 16:24               ` Suresh Siddha
2012-08-07 17:28                 ` Robert Richter
2012-08-07 17:47                   ` Suresh Siddha
2012-08-07 17:45                 ` Eric W. Biederman
2012-08-07 20:57                   ` Borislav Petkov
2012-08-07 22:39                     ` Suresh Siddha
2012-08-08  8:58                       ` Robert Richter
2012-08-08 11:04                         ` Borislav Petkov
2012-08-08 19:16                           ` Suresh Siddha
2012-08-14 17:02                             ` [tip:x86/urgent] x86, apic: fix broken legacy interrupts in the logical apic mode tip-bot for Suresh Siddha
2012-06-06 17:20         ` [PATCH 1/2] x86, irq: update irq_cfg domain unless the new affinity is a subset of the current domain Alexander Gordeev
2012-06-06 23:02           ` Suresh Siddha
2012-06-16  0:25           ` Suresh Siddha
2012-06-18  9:17             ` Alexander Gordeev
2012-06-19  0:51               ` Suresh Siddha
2012-06-19 23:43                 ` [PATCH 1/2] x86, apic: optimize cpu traversal in __assign_irq_vector() using domain membership Suresh Siddha
2012-06-19 23:43                   ` [PATCH 2/2] x86, x2apic: limit the vector reservation to the user specified mask Suresh Siddha
2012-06-20  5:56                     ` Yinghai Lu
2012-06-21  9:04                     ` Alexander Gordeev
2012-06-21 21:51                       ` Suresh Siddha
2012-06-20  5:53                   ` [PATCH 1/2] x86, apic: optimize cpu traversal in __assign_irq_vector() using domain membership Yinghai Lu
2012-06-21  8:31                   ` Alexander Gordeev
2012-06-21 21:53                     ` Suresh Siddha
2012-06-20  0:18               ` [PATCH 1/2] x86, irq: update irq_cfg domain unless the new affinity is a subset of the current domain Suresh Siddha
2012-06-21 11:00                 ` Alexander Gordeev
2012-06-21 21:58                   ` Suresh Siddha
2012-05-22 10:12       ` [PATCH 2/3] x86: x2apic/cluster: Make use of lowest priority delivery mode Alexander Gordeev
2012-05-21  8:22 ` Ingo Molnar
2012-05-21  9:36   ` Alexander Gordeev [this message]
2012-05-21 12:40     ` Ingo Molnar
2012-05-21 14:48       ` Alexander Gordeev
2012-05-21 14:59         ` Ingo Molnar
2012-05-21 15:22           ` Alexander Gordeev
2012-05-21 15:34           ` Cyrill Gorcunov
2012-05-21 15:36           ` Linus Torvalds
2012-05-21 18:07             ` Suresh Siddha
2012-05-21 18:18               ` Linus Torvalds
2012-05-21 18:37                 ` Suresh Siddha
2012-05-21 19:30                   ` Ingo Molnar
2012-05-21 19:15             ` Ingo Molnar
2012-05-21 19:56               ` Suresh Siddha

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