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powerpc/pseries: RE-enable Virtual Processor Home Node updating

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The new PRRN firmware feature provides a more convenient and event-driven
interface than VPHN for notifying Linux of changes to the NUMA affinity of
platform resources. However, for practical reasons, it may not be feasible
for some customers to update to the latest firmware. For these customers,
the VPHN feature supported on previous firmware versions may still be the
best option.

The VPHN feature was previously disabled due to races with the load
balancing code when accessing the NUMA cpu maps, but the new stop_machine()
approach protects the NUMA cpu maps from these concurrent accesses. It
should be safe to re-enable this feature now.

Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Jesse Larrew 2013-04-24 06:05:22 +00:00 • committed by Benjamin Herrenschmidt
commit b7abef045f
1 changed files with 1 additions and 2 deletions
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3
arch/powerpc/mm/numa.c
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@ -1572,9 +1572,8 @@ int start_topology_update(void)
vphn_enabled = 0; vphn_enabled = 0;
rc = of_reconfig_notifier_register(&dt_update_nb); rc = of_reconfig_notifier_register(&dt_update_nb);
} }
} else if (0 && firmware_has_feature(FW_FEATURE_VPHN) && } else if (firmware_has_feature(FW_FEATURE_VPHN) &&
get_lppaca()->shared_proc) { get_lppaca()->shared_proc) {
/* Disabled until races with load balancing are fixed */
if (!vphn_enabled) { if (!vphn_enabled) {
prrn_enabled = 0; prrn_enabled = 0;
vphn_enabled = 1; vphn_enabled = 1;