Re: [PATCH v3] RISC-V: Show IPI stats

[Atish Patra]

On 10/1/18 9:42 AM, Palmer Dabbelt wrote:

On Fri, 28 Sep 2018 23:26:05 PDT (-0700), a...@brainfault.org wrote:

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

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

Changes since v2:
  - Remove use of IPI_CALL_WAKEUP because it's being removed

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

Reviewed-by: Palmer Dabbelt <pal...@sifive.com>

This is going in through Atish's patch set.

Sent.

Regards,
Atish

---
  arch/riscv/include/asm/smp.h |  9 +++++++++
  arch/riscv/kernel/irq.c      |  8 ++++++++
  arch/riscv/kernel/smp.c      | 39 +++++++++++++++++++++++++++++-------
  3 files changed, 49 insertions(+), 7 deletions(-)

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index fce312ce3516..5278ae8f1346 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -25,8 +25,13 @@
  extern unsigned long __cpuid_to_hardid_map[NR_CPUS];
  #define cpuid_to_hardid_map(cpu)    __cpuid_to_hardid_map[cpu]

+struct seq_file;
+
  #ifdef CONFIG_SMP

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

@@ -47,6 +52,10 @@ void riscv_cpuid_to_hartid_mask(const struct cpumask *in, 
struct cpumask *out);

  #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 ca4593317e45..48e6b7db83a1 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)
  {
        struct pt_regs *old_regs = set_irq_regs(regs);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 89d95866f562..686fa7a427ff 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -22,22 +22,24 @@
  #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>
  #include <asm/cacheflush.h>

-/* A collection of single bit ipi messages.  */
-static struct {
-       unsigned long bits ____cacheline_aligned;
-} ipi_data[NR_CPUS] __cacheline_aligned;
-
  enum ipi_message_type {
        IPI_RESCHEDULE,
        IPI_CALL_FUNC,
        IPI_MAX
  };

+/* 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;
+
  int riscv_hartid_to_cpuid(int hartid)
  {
        int i = -1;
@@ -67,6 +69,7 @@ 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);
@@ -81,11 +84,15 @@ 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);

@@ -111,6 +118,24 @@ 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",
+};
+
+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);