From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Scott Cheloha <cheloha@linux.ibm.com>,
Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Laurent Dufour <ldufour@linux.vnet.ibm.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 1/1] powerpc/smp: Set numa node before updating mask
Date: Thu, 8 Apr 2021 16:41:50 +0530 [thread overview]
Message-ID: <20210408111150.GK2339179@linux.vnet.ibm.com> (raw)
In-Reply-To: <878s5tlvxr.fsf@linux.ibm.com>
* Nathan Lynch <nathanl@linux.ibm.com> [2021-04-07 14:46:24]:
> Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
>
> > * Nathan Lynch <nathanl@linux.ibm.com> [2021-04-07 07:19:10]:
> >
> >> Sorry for the delay in following up here.
> >>
> >
> > No issues.
> >
> >> >> So I'd suggest that pseries_add_processor() be made to update
> >> >> these things when the CPUs are marked present, before onlining them.
> >> >
> >> > In pseries_add_processor, we are only marking the cpu as present. i.e
> >> > I believe numa_setup_cpu() would not have been called. So we may not have a
> >> > way to associate the CPU to the node. Otherwise we will have to call
> >> > numa_setup_cpu() or the hcall_vphn.
> >> >
> >> > We could try calling numa_setup_cpu() immediately after we set the
> >> > CPU to be present, but that would be one more extra hcall + I dont know if
> >> > there are any more steps needed before CPU being made present and
> >> > associating the CPU to the node.
> >>
> >> An additional hcall in this path doesn't seem too expensive.
> >>
> >> > Are we sure the node is already online?
> >>
> >> I see that dlpar_online_cpu() calls find_and_online_cpu_nid(), so yes I
> >> think that's covered.
> >
> > Okay,
> >
> > Can we just call set_cpu_numa_node() at the end of map_cpu_to_node().
> > The advantage would be the update to numa_cpu_lookup_table and cpu_to_node
> > would happen at the same time and would be in sync.
>
> I don't know. I guess this question just makes me wonder whether powerpc
> needs to have the additional lookup table. How is it different from the
> generic per_cpu numa_node?
lookup table is for early cpu to node i.e when per_cpu variables may not be
available. This would mean that calling set_numa_node/set_cpu_numa_node from
map_cpu_to_node() may not always be an option, since map_cpu_to_node() does
end up getting called very early in the system.
--
Thanks and Regards
Srikar Dronamraju
next prev parent reply other threads:[~2021-04-08 11:12 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
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 [this message]
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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