Source file `topology.ml`

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(*
 * Copyright (c) 2022 Christiano Haesbaert <haesbaert@haesbaert.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *)

external get_ids : unit -> int list = "caml_get_affinity"

external set_ids : int list -> unit = "caml_set_affinity"

let t =
  (* save oldset so we can restore later *)
  let oldset = get_ids () in
  let topology =
    List.map
      (fun id ->
        set_ids [ id ];
        (* pin ourselves to one cpu *)
        let _, ebx, _, _ = Amd64.cpuid 1 in
        let apicid = Int.shift_right ebx 24 in
        (* read this cpu apicid *)
        let smt, core, socket = Amd64.decompose_apic apicid in
        let _, _, _, edx = Amd64.cpuid 7 in
        let kind =
          if Amd64.cpu_vendor = "GenuineIntel" then
            (* only intel has hybrids *)
            let hybrid = edx land Int.shift_left 1 15 <> 0 in
            if not hybrid then Cpu.P_core
            else
              let eax, _, _, _ = Amd64.cpuid 0x1A in
              match Int.shift_right_logical eax 24 with
              | 0x20 -> Cpu.E_core
              | 0x40 -> Cpu.P_core
              | _ -> Cpu.P_core (* best guess *)
          else (* AMD *)
            Cpu.P_core
        in
        Cpu.make ~id ~kind ~smt ~core ~socket )
      oldset
  in
  set_ids oldset;
  (* restore old set so we can run anywhere *)
  topology