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x86/smp: Enhance native_send_call_func_ipi() 

Nadav noticed that the cpumask allocations in native_send_call_func_ipi()
are noticeable in microbenchmarks.

Use the new cpumask_or_equal() function to simplify the decision whether
the supplied target CPU mask is either equal to cpu_online_mask or equal to
cpu_online_mask except for the CPU on which the function is invoked.

cpumask_or_equal() or's the target mask and the cpumask of the current CPU
together and compares it to cpu_online_mask.

If the result is false, use the mask based IPI function, otherwise check
whether the current CPU is set in the target mask and invoke either the
send_IPI_all() or the send_IPI_allbutselt() APIC callback.

Make the shorthand decision also depend on the static key which enables
shorthand mode. That allows to remove the extra cpumask comparison with
cpu_callout_mask.

Reported-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190722105220.768238809@linutronix.de
This commit is contained in:
Thomas Gleixner 2019-07-22 20:47:26 +02:00
parent d0a7166bc7
commit 832df3d47b
1 changed files with 11 additions and 13 deletions
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22
arch/x86/kernel/apic/ipi.c
View File

@ -83,23 +83,21 @@ void native_send_call_func_single_ipi(int cpu)
void native_send_call_func_ipi(const struct cpumask *mask) void native_send_call_func_ipi(const struct cpumask *mask)
{ {
cpumask_var_t allbutself; if (static_branch_likely(&apic_use_ipi_shorthand)) {
unsigned int cpu = smp_processor_id();
if (!alloc_cpumask_var(&allbutself, GFP_ATOMIC)) { if (!cpumask_or_equal(mask, cpumask_of(cpu), cpu_online_mask))
apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR); goto sendmask;
if (cpumask_test_cpu(cpu, mask))
apic->send_IPI_all(CALL_FUNCTION_VECTOR);
else if (num_online_cpus() > 1)
apic->send_IPI_allbutself(CALL_FUNCTION_VECTOR);
return; return;
} }
cpumask_copy(allbutself, cpu_online_mask); sendmask:
__cpumask_clear_cpu(smp_processor_id(), allbutself);
if (cpumask_equal(mask, allbutself) &&
cpumask_equal(cpu_online_mask, cpu_callout_mask))
apic->send_IPI_allbutself(CALL_FUNCTION_VECTOR);
else
apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR); apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR);
free_cpumask_var(allbutself);
} }
#endif /* CONFIG_SMP */ #endif /* CONFIG_SMP */