From: John Garry <john.garry@huawei.com>
To: Ming Lei <tom.leiming@gmail.com>, <longli@linuxonhyperv.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Keith Busch <keith.busch@intel.com>, Jens Axboe <axboe@fb.com>,
"Christoph Hellwig" <hch@lst.de>,
Sagi Grimberg <sagi@grimberg.me>,
linux-nvme <linux-nvme@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Long Li <longli@microsoft.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
chenxiang <chenxiang66@hisilicon.com>
Subject: Re: [PATCH 0/3] fix interrupt swamp in NVMe
Date: Tue, 20 Aug 2019 09:59:32 +0100 [thread overview]
Message-ID: <fd7d6101-37f4-2d34-f2f7-cfeade610278@huawei.com> (raw)
In-Reply-To: <CACVXFVPCiTU0mtXKS0fyMccPXN6hAdZNHv6y-f8-tz=FE=BV=g@mail.gmail.com>
On 20/08/2019 09:25, Ming Lei wrote:
> On Tue, Aug 20, 2019 at 2:14 PM <longli@linuxonhyperv.com> wrote:
>>
>> From: Long Li <longli@microsoft.com>
>>
>> This patch set tries to fix interrupt swamp in NVMe devices.
>>
>> On large systems with many CPUs, a number of CPUs may share one NVMe hardware
>> queue. It may have this situation where several CPUs are issuing I/Os, and
>> all the I/Os are returned on the CPU where the hardware queue is bound to.
>> This may result in that CPU swamped by interrupts and stay in interrupt mode
>> for extended time while other CPUs continue to issue I/O. This can trigger
>> Watchdog and RCU timeout, and make the system unresponsive.
>>
>> This patch set addresses this by enforcing scheduling and throttling I/O when
>> CPU is starved in this situation.
>>
>> Long Li (3):
>> sched: define a function to report the number of context switches on a
>> CPU
>> sched: export idle_cpu()
>> nvme: complete request in work queue on CPU with flooded interrupts
>>
>> drivers/nvme/host/core.c | 57 +++++++++++++++++++++++++++++++++++++++-
>> drivers/nvme/host/nvme.h | 1 +
>> include/linux/sched.h | 2 ++
>> kernel/sched/core.c | 7 +++++
>> 4 files changed, 66 insertions(+), 1 deletion(-)
>
> Another simpler solution may be to complete request in threaded interrupt
> handler for this case. Meantime allow scheduler to run the interrupt thread
> handler on CPUs specified by the irq affinity mask, which was discussed by
> the following link:
>
> https://lore.kernel.org/lkml/e0e9478e-62a5-ca24-3b12-58f7d056383e@huawei.com/
>
> Could you try the above solution and see if the lockup can be avoided?
> John Garry
> should have workable patch.
Yeah, so we experimented with changing the interrupt handling in the
SCSI driver I maintain to use a threaded handler IRQ handler plus patch
below, and saw a significant throughput boost:
--->8
Subject: [PATCH] genirq: Add support to allow thread to use hard irq
affinity
Currently the cpu allowed mask for the threaded part of a threaded irq
handler will be set to the effective affinity of the hard irq.
Typically the effective affinity of the hard irq will be for a single
cpu. As such, the threaded handler would always run on the same cpu as
the hard irq.
We have seen scenarios in high data-rate throughput testing that the
cpu handling the interrupt can be totally saturated handling both the
hard interrupt and threaded handler parts, limiting throughput.
Add IRQF_IRQ_AFFINITY flag to allow the driver requesting the threaded
interrupt to decide on the policy of which cpu the threaded handler
may run.
Signed-off-by: John Garry <john.garry@huawei.com>
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 5b8328a99b2a..48e8b955989a 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -61,6 +61,9 @@
* interrupt handler after suspending interrupts. For
system
* wakeup devices users need to implement wakeup
detection in
* their interrupt handlers.
+ * IRQF_IRQ_AFFINITY - Use the hard interrupt affinity for setting the cpu
+ * allowed mask for the threaded handler of a threaded
interrupt
+ * handler, rather than the effective hard irq affinity.
*/
#define IRQF_SHARED 0x00000080
#define IRQF_PROBE_SHARED 0x00000100
@@ -74,6 +77,7 @@
#define IRQF_NO_THREAD 0x00010000
#define IRQF_EARLY_RESUME 0x00020000
#define IRQF_COND_SUSPEND 0x00040000
+#define IRQF_IRQ_AFFINITY 0x00080000
#define IRQF_TIMER (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index e8f7f179bf77..cb483a055512 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -966,9 +966,13 @@ irq_thread_check_affinity(struct irq_desc *desc,
struct irqaction *action)
* mask pointer. For CPU_MASK_OFFSTACK=n this is optimized out.
*/
if (cpumask_available(desc->irq_common_data.affinity)) {
+ struct irq_data *irq_data = &desc->irq_data;
const struct cpumask *m;
- m = irq_data_get_effective_affinity_mask(&desc->irq_data);
+ if (action->flags & IRQF_IRQ_AFFINITY)
+ m = desc->irq_common_data.affinity;
+ else
+ m = irq_data_get_effective_affinity_mask(irq_data);
cpumask_copy(mask, m);
} else {
valid = false;
--
2.17.1
As Ming mentioned in that same thread, we could even make this policy
for managed interrupts.
Cheers,
John
>
> Thanks,
> Ming Lei
>
> .
>
next prev parent reply other threads:[~2019-08-20 8:59 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-20 6:14 [PATCH 0/3] fix interrupt swamp in NVMe longli
2019-08-20 6:14 ` [PATCH 1/3] sched: define a function to report the number of context switches on a CPU longli
2019-08-20 9:38 ` Peter Zijlstra
2019-08-21 8:20 ` Long Li
2019-08-21 10:34 ` Peter Zijlstra
2019-08-20 9:39 ` Peter Zijlstra
2019-08-20 6:14 ` [PATCH 2/3] sched: export idle_cpu() longli
2019-08-20 6:14 ` [PATCH 3/3] nvme: complete request in work queue on CPU with flooded interrupts longli
2019-08-20 9:52 ` Peter Zijlstra
2019-08-21 8:37 ` Long Li
2019-08-21 10:35 ` Peter Zijlstra
2019-08-20 17:33 ` Sagi Grimberg
2019-08-21 8:39 ` Long Li
2019-08-21 17:36 ` Long Li
2019-08-21 21:54 ` Sagi Grimberg
2019-08-24 0:13 ` Long Li
2019-08-23 3:21 ` Ming Lei
2019-08-24 0:27 ` Long Li
2019-08-24 12:55 ` Ming Lei
2019-08-20 8:25 ` [PATCH 0/3] fix interrupt swamp in NVMe Ming Lei
2019-08-20 8:59 ` John Garry [this message]
2019-08-20 15:05 ` Keith Busch
2019-08-21 7:47 ` Long Li
2019-08-21 9:44 ` Ming Lei
2019-08-21 10:03 ` John Garry
2019-08-21 16:27 ` Long Li
2019-08-22 1:33 ` Ming Lei
2019-08-22 2:00 ` Keith Busch
2019-08-22 2:23 ` Ming Lei
2019-08-22 9:48 ` Thomas Gleixner
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