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authorFernando Luis Vázquez Cao <fernando@oss.ntt.co.jp>2011-12-13 11:51:53 +0900
committerIngo Molnar <mingo@elte.hu>2011-12-14 09:32:05 +0100
commit346b46be5f10e4d247160ea94ac34450be60ce1e (patch)
treee7515a97d2f0da032c8e1d1371aa94e866c50065 /arch/x86/kernel/irq.c
parentb95a7bd700466c10fda84acbd33f70cf66ec91ce (diff)
downloadop-kernel-dev-346b46be5f10e4d247160ea94ac34450be60ce1e.zip
op-kernel-dev-346b46be5f10e4d247160ea94ac34450be60ce1e.tar.gz
x86: Add per-cpu stat counter for APIC ICR read tries
In the IPI delivery slow path (NMI delivery) we retry the ICR read to check for delivery completion a limited number of times. [ The reason for the limited retries is that some of the places where it is used (cpu boot, kdump, etc) IPI delivery might not succeed (due to a firmware bug or system crash, for example) and in such a case it is better to give up and resume execution of other code. ] This patch adds a new entry to /proc/interrupts, RTR, which tells user space the number of times we retried the ICR read in the IPI delivery slow path. This should give some insight into how well the APIC message delivery hardware is working - if the counts are way too large then we are hitting a (very-) slow path way too often. Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp> Cc: Jörn Engel <joern@logfs.org> Cc: Suresh Siddha <suresh.b.siddha@intel.com> Link: http://lkml.kernel.org/n/tip-vzsp20lo2xdzh5f70g0eis2s@git.kernel.org [ extended the changelog ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/kernel/irq.c')
-rw-r--r--arch/x86/kernel/irq.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 429e0c9..4bbf162 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -74,6 +74,10 @@ int arch_show_interrupts(struct seq_file *p, int prec)
for_each_online_cpu(j)
seq_printf(p, "%10u ", irq_stats(j)->apic_irq_work_irqs);
seq_printf(p, " IRQ work interrupts\n");
+ seq_printf(p, "%*s: ", prec, "RTR");
+ for_each_online_cpu(j)
+ seq_printf(p, "%10u ", per_cpu(icr_read_retry_count, j));
+ seq_printf(p, " APIC ICR read retries\n");
#endif
if (x86_platform_ipi_callback) {
seq_printf(p, "%*s: ", prec, "PLT");
@@ -136,6 +140,7 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
sum += irq_stats(cpu)->irq_spurious_count;
sum += irq_stats(cpu)->apic_perf_irqs;
sum += irq_stats(cpu)->apic_irq_work_irqs;
+ sum += per_cpu(icr_read_retry_count, cpu);
#endif
if (x86_platform_ipi_callback)
sum += irq_stats(cpu)->x86_platform_ipis;
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