Messages in this thread Patch in this message | | | From | Srikar Dronamraju <> | Subject | [PATCH v3 04/11] powerpc/smp: Optimize remove_cpu_from_masks | Date | Thu, 8 Oct 2020 00:07:53 +0530 |
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While offlining a CPU, system currently iterate through all the CPUs in the DIE to clear sibling, l2_cache and smallcore maps. However if there are more cores in a DIE, system can end up spending more time iterating through CPUs which are completely unrelated.
Optimize this by only iterating through smaller but relevant cpumap. If shared_cache is set, cpu_l2_cache_map should be relevant else cpu_sibling_map would be relevant.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Tested-by: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com> Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org> Cc: LKML <linux-kernel@vger.kernel.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Anton Blanchard <anton@ozlabs.org> Cc: Oliver O'Halloran <oohall@gmail.com> Cc: Nathan Lynch <nathanl@linux.ibm.com> Cc: Michael Neuling <mikey@neuling.org> Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com> Cc: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Valentin Schneider <valentin.schneider@arm.com> Cc: Qian Cai <cai@redhat.com> --- arch/powerpc/kernel/smp.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index 8c095fe237b2..2e61a81aad88 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -1263,14 +1263,21 @@ static bool update_mask_by_l2(int cpu, struct cpumask *(*mask_fn)(int)) #ifdef CONFIG_HOTPLUG_CPU static void remove_cpu_from_masks(int cpu) { + struct cpumask *(*mask_fn)(int) = cpu_sibling_mask; int i; - for_each_cpu(i, cpu_cpu_mask(cpu)) { + if (shared_caches) + mask_fn = cpu_l2_cache_mask; + + for_each_cpu(i, mask_fn(cpu)) { set_cpus_unrelated(cpu, i, cpu_l2_cache_mask); set_cpus_unrelated(cpu, i, cpu_sibling_mask); if (has_big_cores) set_cpus_unrelated(cpu, i, cpu_smallcore_mask); - if (has_coregroup_support()) + } + + if (has_coregroup_support()) { + for_each_cpu(i, cpu_coregroup_mask(cpu)) set_cpus_unrelated(cpu, i, cpu_coregroup_mask); } } -- 2.17.1
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