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authorSrikar Dronamraju <srikar@linux.vnet.ibm.com>2020-08-07 13:15:16 +0530
committerMichael Ellerman <mpe@ellerman.id.au>2020-09-16 22:05:18 +1000
commit3babbe447d76ac2919ec4d0eb3b0adfb22f5b03c (patch)
tree2be0fd8efd1fd7d5e971fe11fc01de3aef2f4518 /include/linux/topology.h
parent3db8715ec9dc1d32ecafc67af9fb96508c98efe5 (diff)
sched/topology: Allow archs to override cpu_smt_mask
cpu_smt_mask tracks topology_sibling_cpumask. This would be good for most architectures. One of the users of cpu_smt_mask(), would be to identify idle-cores. On Power9, a pair of SMT4 cores can be presented by the firmware as a SMT8 core for backward compatibility reasons. powerpc allows LPARs to be live migrated from Power8 to Power9. Do note Power8 had only SMT8 cores. Existing software which has been developed/configured for Power8 would expect to see SMT8 core. Maintaining the illusion of SMT8 core is a requirement to make that work. In order to maintain above userspace backward compatibility with previous versions of processor, Power9 onwards there is option to the firmware to advertise a pair of SMT4 cores as a fused cores aka SMT8 core. On Power9 this pair shares the L2 cache as well. However, from the scheduler's point of view, a core should be determined by SMT4, since its a completely independent unit of compute. Hence allow powerpc architecture to override the default cpu_smt_mask() to point to the SMT4 cores in a SMT8 mode. This will ensure the scheduler is always given the right information. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200807074517.27957-1-srikar@linux.vnet.ibm.com
Diffstat (limited to 'include/linux/topology.h')
-rw-r--r--include/linux/topology.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/topology.h b/include/linux/topology.h
index 608fa4aadf0e..ad03df1cc266 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -198,7 +198,7 @@ static inline int cpu_to_mem(int cpu)
#define topology_die_cpumask(cpu) cpumask_of(cpu)
#endif
-#ifdef CONFIG_SCHED_SMT
+#if defined(CONFIG_SCHED_SMT) && !defined(cpu_smt_mask)
static inline const struct cpumask *cpu_smt_mask(int cpu)
{
return topology_sibling_cpumask(cpu);