Re: [PATCH] genirq/affinity: fix node generation from cpumask

From	Balbir Singh <bsingharora@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] genirq/affinity: fix node generation from cpumask
Date	2016-12-15 13:40 +0100
Message-ID	<sODuh-5KH-1@gated-at.bofh.it> (permalink)
References	<sOma6-1ze-31@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw


On 15/12/16 05:01, Guilherme G. Piccoli wrote:
> Commit 34c3d9819fda ("genirq/affinity: Provide smarter irq spreading
> infrastructure") introduced a better IRQ spreading mechanism, taking
> account of the available NUMA nodes in the machine.
> 
> Problem is that the algorithm of retrieving the nodemask iterates
> "linearly" based on the number of online nodes - some architectures
> present non-linear node distribution among the nodemask, like PowerPC.
> If this is the case, the algorithm lead to a wrong node count number
> and therefore to a bad/incomplete IRQ affinity distribution.
> 
> For example, this problem were found in a machine with 128 CPUs and two
> nodes, namely nodes 0 and 8 (instead of 0 and 1, if it was linearly
> distributed). This led to a wrong affinity distribution which then led to
> a bad mq allocation for nvme driver.
> 
> Finally, we take the opportunity to fix a comment regarding the affinity
> distribution when we have _more_ nodes than vectors.

Very good catch! 

Acked-by: Balbir Singh <bsingharora@gmail.com>

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH] genirq/affinity: fix node generation from cpumask "Guilherme G. Piccoli" <gpiccoli@linux.vnet.ibm.com> - 2016-12-14 19:10 +0100
  Re: [PATCH] genirq/affinity: fix node generation from cpumask Gavin Shan <gwshan@linux.vnet.ibm.com> - 2016-12-15 00:30 +0100
    Re: [PATCH] genirq/affinity: fix node generation from cpumask Thomas Gleixner <tglx@linutronix.de> - 2016-12-15 10:40 +0100
      Re: [PATCH] genirq/affinity: fix node generation from cpumask "Guilherme G. Piccoli" <gpiccoli@linux.vnet.ibm.com> - 2016-12-15 15:00 +0100
  Re: [PATCH] genirq/affinity: fix node generation from cpumask Gabriel Krisman Bertazi <gabriel@krisman.be> - 2016-12-15 02:50 +0100
  Re: [PATCH] genirq/affinity: fix node generation from cpumask Christoph Hellwig <hch@lst.de> - 2016-12-15 10:00 +0100
  [tip:irq/urgent] genirq/affinity: Fix node generation from cpumask "tip-bot for Guilherme G. Piccoli" <tipbot@zytor.com> - 2016-12-15 12:40 +0100
  Re: [PATCH] genirq/affinity: fix node generation from cpumask Balbir Singh <bsingharora@gmail.com> - 2016-12-15 13:40 +0100

csiph-web