Messages in this thread | | | Subject | Re: [PATCH -V2] sched,topology: Update sched topology atomically | From | "" <> | Date | Tue, 26 Apr 2022 14:43:45 +0800 |
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Hi, Valentin,
On Mon, 2022-04-25 at 16:52 +0100, Valentin Schneider wrote: > On 21/04/22 08:31, Huang Ying wrote: > > When Peter Zijlstra reviewed commit 0fb3978b0aac ("sched/numa: Fix > > NUMA topology for systems with CPU-less nodes") [1], he pointed out > > that sched_domains_numa_distance and sched_domains_numa_masks are made > > separate RCU variables. That could go side-ways if there were a > > function using both, although there isn't for now. > > > > So we update sched_domains_numa_distance and sched_domains_numa_masks > > and some other related sched topology parameters atomically to address > > the potential issues. > > > > [1] https://lkml.kernel.org/r/20220214121553.582248-1-ying.huang@intel.com > > > > Signed-off-by: "Huang, Ying" <ying.huang@intel.com> > > Suggested-by: Peter Zijlstra <peterz@infradead.org> > > Cc: Valentin Schneider <valentin.schneider@arm.com> > > Cc: Ingo Molnar <mingo@redhat.com> > > Cc: Mel Gorman <mgorman@suse.de> > > Cc: Rik van Riel <riel@surriel.com> > > Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> > > > > Changelog: > > > > v2: > > > > - Addressed comments from Valentin Schneider, Thanks! > > One small bug and a whitespace nit below, with those fixed: > > Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Thanks! Your review comments help me a lot!
> FWIW I briefly tested this vs hotplug on QEMU. > > > @@ -1806,8 +1873,7 @@ void sched_init_numa(int offline_node) > > > > if (distance < LOCAL_DISTANCE || distance >= NR_DISTANCE_VALUES) { > > sched_numa_warn("Invalid distance value range"); > > - bitmap_free(distance_map); > > - return; > > + goto free_bitmap; > > The indentation here is wrong (spaces vs tabs).
Yes. Will fix in the next version.
> > } > > > > bitmap_set(distance_map, distance, 1); > > > /* Compute default topology size */ > > for (i = 0; sched_domain_topology[i].mask; i++); > > After the original boot this will now be the default topology with the NUMA > bits on top, so we'll just keep growing the array every time we hotplug a > node. This should use sched_domain_topology_default instead (ditto for the > copy loop further down). >
Yes. You are right! Thanks for pointing this out. Will fix this in the next version.
Best Regards, Huang, Ying
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