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Subject[PATCH v2] RISC-V: Show IPI stats
Date
This patch provides arch_show_interrupts() implementation to
show IPI stats via /proc/interrupts.

Now the contents of /proc/interrupts" will look like below:
CPU0 CPU1 CPU2 CPU3
8: 17 7 6 14 SiFive PLIC 8 virtio0
10: 10 10 9 11 SiFive PLIC 10 ttyS0
IPI0: 170 673 251 79 Rescheduling interrupts
IPI1: 1 12 27 1 Function call interrupts
IPI2: 0 0 0 0 CPU wake-up interrupts

Signed-off-by: Anup Patel <anup@brainfault.org>
---

Changes since v1:
- Add stub inline show_ipi_stats() function for !CONFIG_SMP
- Make ipi_names[] dynamically sized at compile time
- Minor beautification of ipi_names[] using tabs

arch/riscv/include/asm/smp.h | 9 +++++++++
arch/riscv/kernel/irq.c | 8 ++++++++
arch/riscv/kernel/smp.c | 30 ++++++++++++++++++++++++++++--
3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index 8145b8657d20..37e909c04f47 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -36,6 +36,8 @@ static inline bool can_hotplug_cpu(void)
static inline void arch_send_call_wakeup_ipi(int cpu) { }
#endif

+struct seq_file;
+
#ifdef CONFIG_SMP

enum ipi_message_type {
@@ -48,6 +50,9 @@ enum ipi_message_type {
void send_ipi_message(const struct cpumask *to_whom,
enum ipi_message_type operation);

+/* print IPI stats */
+void show_ipi_stats(struct seq_file *p, int prec);
+
/* SMP initialization hook for setup_arch */
void __init setup_smp(void);

@@ -75,6 +80,10 @@ void boot_sec_cpu(void);

#else

+static inline void show_ipi_stats(struct seq_file *p, int prec)
+{
+}
+
static inline int riscv_hartid_to_cpuid(int hartid)
{
return 0;
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index 7e14b0d9a71d..96202139ade5 100644
--- a/arch/riscv/kernel/irq.c
+++ b/arch/riscv/kernel/irq.c
@@ -8,6 +8,8 @@
#include <linux/interrupt.h>
#include <linux/irqchip.h>
#include <linux/irqdomain.h>
+#include <linux/seq_file.h>
+#include <asm/smp.h>

/*
* Possible interrupt causes:
@@ -24,6 +26,12 @@
*/
#define INTERRUPT_CAUSE_FLAG (1UL << (__riscv_xlen - 1))

+int arch_show_interrupts(struct seq_file *p, int prec)
+{
+ show_ipi_stats(p, prec);
+ return 0;
+}
+
asmlinkage void __irq_entry do_IRQ(struct pt_regs *regs, unsigned long cause)
{
struct pt_regs *old_regs = set_irq_regs(regs);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 629456bb6122..70fd1351d6d9 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -22,6 +22,7 @@
#include <linux/interrupt.h>
#include <linux/smp.h>
#include <linux/sched.h>
+#include <linux/seq_file.h>

#include <asm/sbi.h>
#include <asm/tlbflush.h>
@@ -29,6 +30,7 @@

/* A collection of single bit ipi messages. */
static struct {
+ unsigned long stats[IPI_MAX] ____cacheline_aligned;
unsigned long bits ____cacheline_aligned;
} ipi_data[NR_CPUS] __cacheline_aligned;

@@ -61,6 +63,7 @@ int setup_profiling_timer(unsigned int multiplier)
void riscv_software_interrupt(void)
{
unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
+ unsigned long *stats = ipi_data[smp_processor_id()].stats;

/* Clear pending IPI */
csr_clear(sip, SIE_SSIE);
@@ -75,11 +78,15 @@ void riscv_software_interrupt(void)
if (ops == 0)
return;

- if (ops & (1 << IPI_RESCHEDULE))
+ if (ops & (1 << IPI_RESCHEDULE)) {
+ stats[IPI_RESCHEDULE]++;
scheduler_ipi();
+ }

- if (ops & (1 << IPI_CALL_FUNC))
+ if (ops & (1 << IPI_CALL_FUNC)) {
+ stats[IPI_CALL_FUNC]++;
generic_smp_call_function_interrupt();
+ }

BUG_ON((ops >> IPI_MAX) != 0);

@@ -105,6 +112,25 @@ send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
sbi_send_ipi(cpumask_bits(&hartid_mask));
}

+static const char *ipi_names[] = {
+ [IPI_RESCHEDULE] = "Rescheduling interrupts",
+ [IPI_CALL_FUNC] = "Function call interrupts",
+ [IPI_CALL_WAKEUP] = "CPU wake-up interrupts",
+};
+
+void show_ipi_stats(struct seq_file *p, int prec)
+{
+ unsigned int cpu, i;
+
+ for (i = 0; i < IPI_MAX; i++) {
+ seq_printf(p, "%*s%u:%s", prec - 1, "IPI", i,
+ prec >= 4 ? " " : "");
+ for_each_online_cpu(cpu)
+ seq_printf(p, "%10lu ", ipi_data[cpu].stats[i]);
+ seq_printf(p, " %s\n", ipi_names[i]);
+ }
+}
+
void arch_send_call_function_ipi_mask(struct cpumask *mask)
{
send_ipi_message(mask, IPI_CALL_FUNC);
--
2.17.1
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