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| author | Fernando Luis Vázquez Cao <fernando@oss.ntt.co.jp> | 2011-12-13 02:51:53 (GMT) |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-12-14 08:32:05 (GMT) |
| commit | 346b46be5f10e4d247160ea94ac34450be60ce1e (patch) | |
| tree | e7515a97d2f0da032c8e1d1371aa94e866c50065 /arch/x86 | |
| parent | b95a7bd700466c10fda84acbd33f70cf66ec91ce (diff) | |
| download | linux-fsl-qoriq-346b46be5f10e4d247160ea94ac34450be60ce1e.tar.xz | |
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')
| -rw-r--r-- | arch/x86/include/asm/apic.h | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/apic/apic.c | 6 | ||||
| -rw-r--r-- | arch/x86/kernel/irq.c | 5 |
3 files changed, 14 insertions, 0 deletions
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index 1a6c09a..5fe0bd5 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -410,6 +410,9 @@ extern int wakeup_secondary_cpu_via_nmi(int apicid, unsigned long start_eip); #endif #ifdef CONFIG_X86_LOCAL_APIC + +DECLARE_PER_CPU(unsigned, icr_read_retry_count); + static inline u32 apic_read(u32 reg) { return apic->read(reg); diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index f98d84c..2942794 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -79,6 +79,11 @@ DEFINE_EARLY_PER_CPU(u16, x86_bios_cpu_apicid, BAD_APICID); EXPORT_EARLY_PER_CPU_SYMBOL(x86_cpu_to_apicid); EXPORT_EARLY_PER_CPU_SYMBOL(x86_bios_cpu_apicid); +/* + * ICR read retry counter + */ +DEFINE_PER_CPU(unsigned, icr_read_retry_count); + #ifdef CONFIG_X86_32 /* @@ -250,6 +255,7 @@ u32 native_safe_apic_wait_icr_idle(void) send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY; if (!send_status) break; + percpu_inc(icr_read_retry_count); udelay(100); } while (timeout++ < 1000); 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; |