From: Nathan Lynch <nathanl@linux.ibm.com>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Scott Cheloha <cheloha@linux.ibm.com>,
Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>,
Ingo Molnar <mingo@kernel.org>,
Laurent Dufour <ldufour@linux.vnet.ibm.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Valentin Schneider <valentin.schneider@arm.com>
Subject: Re: [PATCH 1/1] powerpc/smp: Set numa node before updating mask
Date: Thu, 01 Apr 2021 17:51:05 -0500 [thread overview]
Message-ID: <87czvdbova.fsf@linux.ibm.com> (raw)
In-Reply-To: <20210401154200.150077-1-srikar@linux.vnet.ibm.com>
Hi Srikar,
Thanks for figuring this out.
Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
>
> Some of the per-CPU masks use cpu_cpu_mask as a filter to limit the search
> for related CPUs. On a dlpar add of a CPU, update cpu_cpu_mask before
> updating the per-CPU masks. This will ensure the cpu_cpu_mask is updated
> correctly before its used in setting the masks. Setting the numa_node will
> ensure that when cpu_cpu_mask() gets called, the correct node number is
> used. This code movement helped fix the above call trace.
>
>
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 5a4d59a1070d..1a99d75679a8 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -1521,6 +1521,9 @@ void start_secondary(void *unused)
>
> vdso_getcpu_init();
> #endif
> + set_numa_node(numa_cpu_lookup_table[cpu]);
> + set_numa_mem(local_memory_node(numa_cpu_lookup_table[cpu]));
> +
> /* Update topology CPU masks */
> add_cpu_to_masks(cpu);
>
> @@ -1539,9 +1542,6 @@ void start_secondary(void *unused)
> shared_caches = true;
> }
>
> - set_numa_node(numa_cpu_lookup_table[cpu]);
> - set_numa_mem(local_memory_node(numa_cpu_lookup_table[cpu]));
> -
Regardless of your change: at boot time, this set of calls to
set_numa_node() and set_numa_mem() is redundant, right? Because
smp_prepare_cpus() has:
for_each_possible_cpu(cpu) {
...
if (cpu_present(cpu)) {
set_cpu_numa_node(cpu, numa_cpu_lookup_table[cpu]);
set_cpu_numa_mem(cpu,
local_memory_node(numa_cpu_lookup_table[cpu]));
}
I would rather that, when onlining a CPU that happens to have been
dynamically added after boot, we enter start_secondary() with conditions
equivalent to those at boot time. Or as close to that as is practical.
So I'd suggest that pseries_add_processor() be made to update
these things when the CPUs are marked present, before onlining them.
next prev parent reply other threads:[~2021-04-01 22:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 15:42 [PATCH 1/1] powerpc/smp: Set numa node before updating mask Srikar Dronamraju
2021-04-01 22:51 ` Nathan Lynch [this message]
2021-04-02 3:18 ` Srikar Dronamraju
2021-04-07 12:19 ` Nathan Lynch
2021-04-07 16:49 ` Srikar Dronamraju
2021-04-07 19:46 ` Nathan Lynch
2021-04-08 11:11 ` Srikar Dronamraju
2021-04-08 20:00 ` Nathan Lynch
2021-04-09 10:14 ` Srikar Dronamraju
2021-04-13 12:23 ` Nathan Lynch
2021-04-13 12:25 ` Nathan Lynch
2021-04-19 4:00 ` Michael Ellerman
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