vlfi/vlf-tune.el

;;; vlf-tune.el --- VLF tuning operations  -*- lexical-binding: t -*-

;; Copyright (C) 2014 Free Software Foundation, Inc.

;; Keywords: large files, batch size, performance
;; Author: Andrey Kotlarski <m00naticus@gmail.com>
;; URL: https://github.com/m00natic/vlfi

;; This file is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 3, or (at your option)
;; any later version.

;; This file is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to
;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:
;; This package provides wrappers for basic chunk operations that add
;; time statistics and automatic tuning of `vlf-batch-size' for
;; optimal performance.

;;; Code:

(defcustom vlf-tune-enabled t
  "Whether to allow automatic change of batch size.
If nil, completely disable.  If `stats', maintain measure statistics,
but don't change batch size.  If t, measure and change."
  :group 'vlf :type '(choice (const :tag "Enabled" t)
                             (const :tag "Just statistics" stats)
                             (const :tag "Disabled" nil)))

(defun vlf-tune-ram-size ()
  "Try to determine RAM size in bytes."
  (let* ((free-output (shell-command-to-string "free"))
         (match-from (string-match "[[:digit:]]+" free-output)))
    (if match-from
        (* 1000 (string-to-number (substring free-output match-from
                                             (match-end 0)))))))

(defcustom vlf-tune-max (let ((ram-size (vlf-tune-ram-size)))
                          (if ram-size
                              (/ ram-size 20)
                            large-file-warning-threshold))
  "Maximum batch size in bytes when auto tuning."
  :group 'vlf :type 'integer)

(defcustom vlf-tune-step (/ vlf-tune-max 1000)
  "Step used for tuning in bytes."
  :group 'vlf :type 'integer)

(defvar vlf-tune-insert-bps nil
  "Vector of bytes per second insert measurements.")
(make-variable-buffer-local 'vlf-tune-insert-bps)
(put 'vlf-batch-size 'permanent-local t)

(defvar vlf-tune-insert-raw-bps nil
  "Vector of bytes per second non-decode insert measurements.")
(make-variable-buffer-local 'vlf-tune-insert-raw-bps)
(put 'vlf-tune-insert-raw-bps 'permanent-local t)

(defvar vlf-tune-encode-bps nil
  "Vector of bytes per second encode measurements.")
(make-variable-buffer-local 'vlf-tune-encode-bps)
(put 'vlf-tune-encode-bps 'permanent-local t)

(defvar vlf-tune-write-bps nil
  "Vector of bytes per second write measurements.")
(make-variable-buffer-local 'vlf-tune-write-bps)
(put 'vlf-tune-write-bps 'permanent-local t)

(defvar vlf-tune-hexl-bps nil
  "Vector of bytes per second hexlify measurements.")
(make-variable-buffer-local 'vlf-tune-hexl-bps)
(put 'vlf-tune-hexl-bps 'permanent-local t)

(defvar vlf-tune-dehexlify-bps nil
  "Vector of bytes per second dehexlify measurements.")
(make-variable-buffer-local 'vlf-tune-dehexlify-bps)
(put 'vlf-tune-dehexlify-bps 'permanent-local t)

(defun vlf-tune-initialize-measurement ()
  "Initialize measurement vector."
  (make-vector (1- (/ vlf-tune-max vlf-tune-step)) '(0 . 0)))

(defmacro vlf-tune-add-measurement (vec size time)
  "Add at an appropriate position in VEC new SIZE TIME measurement.
VEC is a vector of (mean time . count) elements ordered by size."
  `(when vlf-tune-enabled
     (or ,vec (setq ,vec (vlf-tune-initialize-measurement)))
     (let* ((idx (max 0 (1- (min (round ,size vlf-tune-step) ;closest index
                                 (/ vlf-tune-max vlf-tune-step)))))
            (existing (aref ,vec idx)))
       (aset ,vec idx (let ((count (1+ (cdr existing)))) ;recalculate mean
                        (cons (/ (+ (* (1- count) (car existing))
                                    (/ ,size ,time))
                                 count)
                              count))))))

(defmacro vlf-time (&rest body)
  "Get timing consed with result of BODY execution."
  `(let ((time (float-time))
         (result (progn ,@body)))
     (cons (- (float-time) time) result)))

(defun vlf-tune-insert-file-contents (start end)
  "Extract decoded file bytes START to END and save time it takes."
  (let ((result (vlf-time (insert-file-contents buffer-file-name
                                                nil start end))))
    (vlf-tune-add-measurement vlf-tune-insert-bps
                              (- end start) (car result))
    (cdr result)))

(defun vlf-tune-insert-file-contents-literally (start end)
  "Insert raw file bytes START to END and save time it takes."
  (let ((result (vlf-time (insert-file-contents-literally
                           buffer-file-name nil start end))))
    (vlf-tune-add-measurement vlf-tune-insert-raw-bps
                              (- end start) (car result))
    (cdr result)))

(defun vlf-tune-encode-length (start end)
  "Get length of encoded region START to END and save time it takes."
  (let ((result (vlf-time (length (encode-coding-region
                                   start end
                                   buffer-file-coding-system t)))))
    (vlf-tune-add-measurement vlf-tune-encode-bps
                              (- end start) (car result))
    (cdr result)))

(defun vlf-tune-write (start end append visit size)
  "Save buffer and save time it takes.
START, END, APPEND, VISIT have same meaning as in `write-region'.
SIZE is number of bytes that are saved."
  (let ((time (car (write-region start end buffer-file-name
                                 append visit))))
    (vlf-tune-add-measurement vlf-tune-write-bps size time)))

(defun vlf-tune-hexlify ()
  "Activate `hexl-mode' and save time it takes."
  (let ((time (car (vlf-time (hexl-mode)))))
    (vlf-tune-add-measurement vlf-tune-hexl-bps
                              hexl-max-address time)))

(defun vlf-tune-dehexlify ()
  "Exit `hexl-mode' and save time it takes."
  (let ((time (car (vlf-time (hexl-mode-exit)))))
    (vlf-tune-add-measurement vlf-tune-dehexlify-bps
                              hexl-max-address time)))

(provide 'vlf-tune)

;;; vlf-tune.el ends here