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From: Nitesh Narayan Lal <nitesh@redhat.com>
To: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	peterz@infradead.org
Cc: frederic@kernel.org, mtosatti@redhat.com, juri.lelli@redhat.com,
	abelits@marvell.com, bhelgaas@google.com,
	linux-pci@vger.kernel.org, rostedt@goodmis.org, mingo@kernel.org,
	tglx@linutronix.de, davem@davemloft.net,
	akpm@linux-foundation.org, sfr@canb.auug.org.au,
	stephen@networkplumber.org, rppt@linux.vnet.ibm.com,
	jinyuqi@huawei.com, zhangshaokun@hisilicon.com
Subject: Re: [Patch v4 1/3] lib: Restrict cpumask_local_spread to houskeeping CPUs
Date: Mon, 29 Jun 2020 12:11:25 -0400
Message-ID: <8054aff1-544d-80de-456f-c3e244233419@redhat.com> (raw)
In-Reply-To: <20200625223443.2684-2-nitesh@redhat.com>

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On 6/25/20 6:34 PM, Nitesh Narayan Lal wrote:
> From: Alex Belits <abelits@marvell.com>
>
> The current implementation of cpumask_local_spread() does not respect the
> isolated CPUs, i.e., even if a CPU has been isolated for Real-Time task,
> it will return it to the caller for pinning of its IRQ threads. Having
> these unwanted IRQ threads on an isolated CPU adds up to a latency
> overhead.
>
> Restrict the CPUs that are returned for spreading IRQs only to the
> available housekeeping CPUs.
>
> Signed-off-by: Alex Belits <abelits@marvell.com>
> Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com>

Hi Peter,

I just realized that Yuqi jin's patch [1] that modifies cpumask_local_spread is
lying in linux-next.
Should I do a re-post by re-basing the patches on the top of linux-next?

[1]
https://lore.kernel.org/lkml/1582768688-2314-1-git-send-email-zhangshaokun@hisilicon.com/

> ---
>  lib/cpumask.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/lib/cpumask.c b/lib/cpumask.c
> index fb22fb266f93..85da6ab4fbb5 100644
> --- a/lib/cpumask.c
> +++ b/lib/cpumask.c
> @@ -6,6 +6,7 @@
>  #include <linux/export.h>
>  #include <linux/memblock.h>
>  #include <linux/numa.h>
> +#include <linux/sched/isolation.h>
>  
>  /**
>   * cpumask_next - get the next cpu in a cpumask
> @@ -205,22 +206,27 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask)
>   */
>  unsigned int cpumask_local_spread(unsigned int i, int node)
>  {
> -	int cpu;
> +	int cpu, hk_flags;
> +	const struct cpumask *mask;
>  
> +	hk_flags = HK_FLAG_DOMAIN | HK_FLAG_MANAGED_IRQ;
> +	mask = housekeeping_cpumask(hk_flags);
>  	/* Wrap: we always want a cpu. */
> -	i %= num_online_cpus();
> +	i %= cpumask_weight(mask);
>  
>  	if (node == NUMA_NO_NODE) {
> -		for_each_cpu(cpu, cpu_online_mask)
> +		for_each_cpu(cpu, mask) {
>  			if (i-- == 0)
>  				return cpu;
> +		}
>  	} else {
>  		/* NUMA first. */
> -		for_each_cpu_and(cpu, cpumask_of_node(node), cpu_online_mask)
> +		for_each_cpu_and(cpu, cpumask_of_node(node), mask) {
>  			if (i-- == 0)
>  				return cpu;
> +		}
>  
> -		for_each_cpu(cpu, cpu_online_mask) {
> +		for_each_cpu(cpu, mask) {
>  			/* Skip NUMA nodes, done above. */
>  			if (cpumask_test_cpu(cpu, cpumask_of_node(node)))
>  				continue;
-- 
Nitesh


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  reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-25 22:34 [PATCH v4 0/3] Preventing job distribution to isolated CPUs Nitesh Narayan Lal
2020-06-25 22:34 ` [Patch v4 1/3] lib: Restrict cpumask_local_spread to houskeeping CPUs Nitesh Narayan Lal
2020-06-29 16:11   ` Nitesh Narayan Lal [this message]
2020-07-01  0:32     ` Andrew Morton
2020-07-01  0:47       ` Nitesh Narayan Lal
2020-06-25 22:34 ` [Patch v4 2/3] PCI: Restrict probe functions to housekeeping CPUs Nitesh Narayan Lal
2020-06-25 22:34 ` [Patch v4 3/3] net: Restrict receive packets queuing " Nitesh Narayan Lal
2020-06-26 11:14   ` Peter Zijlstra
2020-06-26 17:20     ` David Miller

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