Re: [PATCH 6/7] psi: pressure stall information for CPU, memory, and IO

Peter Zijlstra
2018-05-09T09:59:38Z

On Mon, May 07, 2018 at 05:01:34PM -0400, Johannes Weiner wrote:
> diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h
> new file mode 100644
> index 000000000000..b22b0ffc729d
> --- /dev/null
> +++ b/include/linux/psi_types.h
> @@ -0,0 +1,84 @@
> +#ifndef _LINUX_PSI_TYPES_H
> +#define _LINUX_PSI_TYPES_H
> +
> +#include <linux/types.h>
> +
> +#ifdef CONFIG_PSI
> +
> +/* Tracked task states */
> +enum psi_task_count {
> + NR_RUNNING,
> + NR_IOWAIT,
> + NR_MEMSTALL,
> + NR_PSI_TASK_COUNTS,
> +};
> +
> +/* Task state bitmasks */
> +#define TSK_RUNNING (1 << NR_RUNNING)
> +#define TSK_IOWAIT (1 << NR_IOWAIT)
> +#define TSK_MEMSTALL (1 << NR_MEMSTALL)
> +
> +/* Resources that workloads could be stalled on */
> +enum psi_res {
> + PSI_CPU,
> + PSI_MEM,
> + PSI_IO,
> + NR_PSI_RESOURCES,
> +};
> +
> +/* Pressure states for a group of tasks */
> +enum psi_state {
> + PSI_NONE, /* No stalled tasks */
> + PSI_SOME, /* Stalled tasks & working tasks */
> + PSI_FULL, /* Stalled tasks & no working tasks */
> + NR_PSI_STATES,
> +};
> +
> +struct psi_resource {
> + /* Current pressure state for this resource */
> + enum psi_state state;
> +
> + /* Start of current state (cpu_clock) */
> + u64 state_start;
> +
> + /* Time sampling buckets for pressure states (ns) */
> + u64 times[NR_PSI_STATES - 1];

Fails to explain why no FULL.

> +};
> +
> +struct psi_group_cpu {
> + /* States of the tasks belonging to this group */
> + unsigned int tasks[NR_PSI_TASK_COUNTS];
> +

AFAICT there's a hole here, that would fit the @nonidle member. Which
also avoids the later hole generated by it.

> + /* Per-resource pressure tracking in this group */
> + struct psi_resource res[NR_PSI_RESOURCES];
> +
> + /* There are runnable or D-state tasks */
> + bool nonidle;

Mandatory complaint about using _Bool in composites goes here.

> + /* Start of current non-idle state (cpu_clock) */
> + u64 nonidle_start;
> +
> + /* Time sampling bucket for non-idle state (ns) */
> + u64 nonidle_time;
> +};
> +
> +struct psi_group {
> + struct psi_group_cpu *cpus;
> +
> + struct delayed_work clock_work;
> + unsigned long period_expires;
> +
> + u64 some[NR_PSI_RESOURCES];
> + u64 full[NR_PSI_RESOURCES];
> +
> + unsigned long avg_some[NR_PSI_RESOURCES][3];
> + unsigned long avg_full[NR_PSI_RESOURCES][3];
> +};