mperf

Bindings to Linux perf's metrics
IN THIS PACKAGE
Module Mperf
module Attr : sig ... end
module KindMap : Map.S with type key = Attr.Kind.t
type flag =
| Fd_cloexec(*

(since Linux 3.14). This flag enables the close-on-exec flag for the created event file descriptor, so that the file descriptor is automatically closed on execve(2). Setting the close-on-exec flags at creation time, rather than later with fcntl(2), avoids potential race conditions where the calling thread invokes perf_event_open() and fcntl(2) at the same time as another thread calls fork(2) then execve(2).

*)
| Fd_no_group(*

This flag allows creating an event as part of an event group but having no group leader. It is unclear why this is useful.

*)
| Fd_output(*

This flag reroutes the output from an event to the group leader.

*)
| Pid_cgroup(*

This flag activates per-container system-wide monitoring. A container is an abstraction that isolates a set of resources for finer-grained control (CPUs, memory, etc.). In this mode, the event is measured only if the thread running on the monitored CPU belongs to the designated container (cgroup). The cgroup is identified by passing a file descriptor opened on its directory in the cgroupfs filesystem. For instance, if the cgroup to monitor is called test, then a file descriptor opened on /dev/cgroup/test (assuming cgroupfs is mounted on /dev/cgroup) must be passed as the pid parameter. cgroup monitoring is available only for system-wide events and may therefore require extra permissions.

*)
type t

Opaque type of an event counter (internally t is a file descriptor). Each file descriptor corresponds to one event that is measured; these can be grouped together to measure multiple events simultaneously.

val make : ?pid:int -> ?cpu:int -> ?group:t -> ?flags:flag list -> Attr.t -> t

make ~pid ~cpu ?group ?flags attr is a perf event counter. Refer to perf_event_open(2) for the description of the arguments. One counter only counts one kind of attribute at a time. If you want to simultanously count different metrics (like the perf stat tool does), you have to setup several counters.

val kind : t -> Attr.Kind.t

kind c is the kind of events that this counter counts.

val read : t -> int64

read c is the value of the counter c.

val reset : t -> unit

reset c sets c to zero.

val enable : t -> unit

Start measuring.

val disable : t -> unit

Disabling an event. When an event is disabled it does not count or generate overflows but does continue to exist and maintain its count value.

val close : t -> unit

Free resources associated with a counter.

type execution = private {
process_status : Unix.process_status;
stdout : string;
stderr : string;
data : Int64.t KindMap.t;
}

Type returned by with_process

val with_process : ?env:string list -> ?timeout:int -> ?stdout:string -> ?stderr:string -> string list -> Attr.t list -> [ `Ok of execution | `Timeout | `Exn of exn ]

with_process ?env ?timeout ?stdout ?stderr cmd attrs is the result of the execution of the program described by cmd. This can either be a successful execution, or an error.

val enable_all : unit -> unit

A process can enable or disable all the event groups that are attached to it using the prctl(2) PR_TASK_PERF_EVENTS_ENABLE and PR_TASK_PERF_EVENTS_DISABLE operations. This applies to all counters on the calling process, whether created by this process or by another, and does not affect any counters that this process has created on other processes. It enables or disables only the group leaders, not any other members in the groups.

val disable_all : unit -> unit