LinuxPPC-Dev Archive on lore.kernel.org
 help / color / Atom feed
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
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.

  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01 15:42 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

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:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

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

  git send-email \
    --in-reply-to=87czvdbova.fsf@linux.ibm.com \
    --to=nathanl@linux.ibm.com \
    --cc=Geetika.Moolchandani1@ibm.com \
    --cc=cheloha@linux.ibm.com \
    --cc=ego@linux.vnet.ibm.com \
    --cc=ldufour@linux.vnet.ibm.com \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mingo@kernel.org \
    --cc=peterz@infradead.org \
    --cc=srikar@linux.vnet.ibm.com \
    --cc=valentin.schneider@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

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

LinuxPPC-Dev Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linuxppc-dev/0 linuxppc-dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linuxppc-dev linuxppc-dev/ https://lore.kernel.org/linuxppc-dev \
		linuxppc-dev@lists.ozlabs.org linuxppc-dev@ozlabs.org
	public-inbox-index linuxppc-dev

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.ozlabs.lists.linuxppc-dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git