From 346b46be5f10e4d247160ea94ac34450be60ce1e Mon Sep 17 00:00:00 2001 From: =?utf8?q?Fernando=20Luis=20V=C3=A1zquez=20Cao?= Date: Tue, 13 Dec 2011 11:51:53 +0900 Subject: [PATCH] x86: Add per-cpu stat counter for APIC ICR read tries MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Cc: Jörn Engel Cc: Suresh Siddha Link: http://lkml.kernel.org/n/tip-vzsp20lo2xdzh5f70g0eis2s@git.kernel.org [ extended the changelog ] Signed-off-by: Ingo Molnar --- arch/x86/include/asm/apic.h | 3 +++ arch/x86/kernel/apic/apic.c | 6 ++++++ arch/x86/kernel/irq.c | 5 +++++ 3 files changed, 14 insertions(+) diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index 1a6c09af048f..5fe0bd574756 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 f98d84caf94c..2942794a9a52 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 429e0c92924e..4bbf1627905b 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; -- 2.34.1