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Date: Thu, 13 Sep 2018 10:51:54 -0700
From: Atish Patra <atish.patra@....com>
To: Anup Patel <anup@...infault.org>,
Palmer Dabbelt <palmer@...ive.com>,
Albert Ou <aou@...s.berkeley.edu>
Cc: Christoph Hellwig <hch@...radead.org>,
"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] RISC-V: Show IPI stats
On 9/12/18 7:37 AM, Anup Patel 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
> IPI2: 0 0 0 0 CPU wake-up interrupts
>
> Signed-off-by: Anup Patel <anup@...infault.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",
There were some concerns about cpu hotplug patch which introduced
IPI_CALL_WAKEUP. I have dropped it as of now from my series. I will send
it as a separate patch. So we may want to add IPI_CALL_WAKEUP along with
cpu hotplug patch which makes more sense to me.
Other than that, LGTM.
Regards,
Atish
> +};
> +
> +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);
>
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