LKML Archive on
help / color / mirror / Atom feed
From: Jesse Brandeburg <>
Subject: [PATCH] genirq: set initial affinity when hinting
Date: Thu, 18 Dec 2014 17:22:06 -0800	[thread overview]
Message-ID: <> (raw)

The default behavior of the kernel is somewhat undesirable as all
requested interrupts end up on CPU0 after registration.  A user can
run irqbalance daemon, or can manually configure smp_affinity via the
proc filesystem, but the default affinity of the interrupts for all
devices is always CPU zero, this can cause performance problems or
very heavy cpu use of only one core if not noticed and fixed by the

This patch enables the setting of the initial affinity directly
when the driver sets a hint.

This enabling means that kernel drivers can include an initial
affinity setting for the interrupt, instead of all interrupts starting
out life on CPU0. Of course if irqbalance is still running then the
interrupts will get moved as before.

This function is currently called by drivers in block, crypto,
infiniband, ethernet and scsi trees, but only a handful, so these will
be the devices affected by this change.

Tested on i40e, and default interrupts were spread across the CPUs
according to the hint.


Signed-off-by: Jesse Brandeburg <>
CC: Thomas Gleixner <>
 kernel/irq/manage.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 8069237..f038e58 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -243,6 +243,8 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
 		return -EINVAL;
 	desc->affinity_hint = m;
 	irq_put_desc_unlock(desc, flags);
+	/* set the initial affinity to prevent every interrupt being on CPU0 */
+	__irq_set_affinity(irq, m, false);
 	return 0;

             reply	other threads:[~2014-12-19  1:22 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-19  1:22 Jesse Brandeburg [this message]
2014-12-19 19:53 ` Jesse Brandeburg
2015-01-23 10:42 ` [tip:irq/core] genirq: Set initial affinity in irq_set_affinity_hint() tip-bot for Jesse Brandeburg
2015-01-28  6:36   ` Yinghai Lu
2015-01-28 16:43     ` Jesse Brandeburg
2015-01-28 19:58     ` Jesse Brandeburg
2015-02-09  8:22       ` Ingo Molnar
2015-02-09 17:48         ` Ingo Molnar

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \
    --subject='Re: [PATCH] genirq: set initial affinity when hinting' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).