From: Xiongfeng Wang <wangxiongfeng2@huawei.com>
To: <tglx@linutronix.de>, <maz@kernel.org>
Cc: <linux-kernel@vger.kernel.org>, <wangxiongfeng2@huawei.com>,
<guohanjun@huawei.com>
Subject: [PATCH] irqchip/gic-v3-its: Select housekeeping CPUs preferentially for managed IRQs
Date: Mon, 24 Jan 2022 15:34:40 +0800 [thread overview]
Message-ID: <20220124073440.88598-1-wangxiongfeng2@huawei.com> (raw)
When using kernel parameter 'isolcpus=managed_irq,xxxx' to bind the
managed IRQs to housekeeping CPUs, the effective_affinity sometimes
still contains the non-housekeeping CPUs.
irq_do_set_affinity() passes the housekeeping cpumask to
chip->irq_set_affinity(), but ITS driver select CPU according to
irq_common_data->affinity. While 'irq_common_data->affinity' is updated
after chip->irq_set_affinity() is called in irq_do_set_affinity(). Also
'irq_common_data->affinity' may contains non-housekeeping CPUs. I found
the below link explaining the reason.
https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2267032.html
To modify CPU selecting logic to prefer housekeeping CPUs, select CPU
from the input cpumask parameter first. If none of it is online, then
select CPU from 'irq_common_data->affinity'.
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
---
drivers/irqchip/irq-gic-v3-its.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index d25b7a864bbb..17c15d3b2784 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -1624,7 +1624,10 @@ static int its_select_cpu(struct irq_data *d,
cpu = cpumask_pick_least_loaded(d, tmpmask);
} else {
- cpumask_and(tmpmask, irq_data_get_affinity_mask(d), cpu_online_mask);
+ cpumask_and(tmpmask, aff_mask, cpu_online_mask);
+ if (cpumask_empty(tmpmask))
+ cpumask_and(tmpmask, irq_data_get_affinity_mask(d),
+ cpu_online_mask);
/* If we cannot cross sockets, limit the search to that node */
if ((its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) &&
--
2.20.1
next reply other threads:[~2022-01-24 7:18 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-24 7:34 Xiongfeng Wang [this message]
2022-01-24 11:24 ` [PATCH] irqchip/gic-v3-its: Select housekeeping CPUs preferentially for managed IRQs Marc Zyngier
2022-01-25 12:49 ` Xiongfeng Wang
2022-01-25 13:31 ` Marc Zyngier
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