dirstate: Remove the flat Rust DirstateMap implementation
Before this changeset we had two Rust implementations of `DirstateMap`.
This removes the "flat" DirstateMap so that the "tree" DirstateMap is always
used when Rust enabled. This simplifies the code a lot, and will enable
(in the next changeset) further removal of a trait abstraction.
This is a performance regression when:
* Rust is enabled, and
* The repository uses the legacy dirstate-v1 file format, and
* For `hg status`, unknown files are not listed (such as with `-mard`)
The regression is about 100 milliseconds for `hg status -mard` on a
semi-large repository (mozilla-central), from ~320ms to ~420ms.
We deem this to be small enough to be worth it.
The new dirstate-v2 is still experimental at this point, but we aim to
stabilize it (though not yet enable it by default for new repositories)
in Mercurial 6.0. Eventually, upgrating repositories to dirsate-v2 will
eliminate this regression (and enable other performance improvements).
# Background
The flat DirstateMap was introduced with the first Rust implementation of the
status algorithm. It works similarly to the previous Python + C one, with a
single `HashMap` that associates file paths to a `DirstateEntry` (where Python
has a dict).
We later added the tree DirstateMap where the root of the tree contains nodes
for files and directories that are directly at the root of the repository,
and nodes for directories can contain child nodes representing the files and
directly that *they* contain directly. The shape of this tree mirrors that of
the working directory in the filesystem. This enables the status algorithm to
traverse this tree in tandem with traversing the filesystem tree, which in
turns enables a more efficient algorithm.
Furthermore, the new dirstate-v2 file format is also based on a tree of the
same shape. The tree DirstateMap can access a dirstate-v2 file without parsing
it: binary data in a single large (possibly memory-mapped) bytes buffer is
traversed on demand. This allows `DirstateMap` creation to take `O(1)` time.
(Mutation works by creating new in-memory nodes with copy-on-write semantics,
and serialization is append-mostly.)
The tradeoff is that for "legacy" repositories that use the dirstate-v1 file
format, parsing that file into a tree DirstateMap takes more time. Profiling
shows that this time is dominated by `HashMap`. For a dirstate containing `F`
files with an average `D` directory depth, the flat DirstateMap does parsing
in `O(F)` number of HashMap operations but the tree DirstateMap in `O(F × D)`
operations, since each node has its own HashMap containing its child nodes.
This slower costs ~140ms on an old snapshot of mozilla-central, and ~80ms
on an old snapshot of the Netbeans repository.
The status algorithm is faster, but with `-mard` (when not listing unknown
files) it is typically not faster *enough* to compensate the slower parsing.
Both Rust implementations are always faster than the Python + C implementation
# Benchmark results
All benchmarks are run on changeset 98c0408324e6, with repositories that use
the dirstate-v1 file format, on a server with 4 CPU cores and 4 CPU threads
(no HyperThreading).
`hg status` benchmarks show wall clock times of the entire command as the
average and standard deviation of serveral runs, collected by
https://github.com/sharkdp/hyperfine and reformated.
Parsing benchmarks are wall clock time of the Rust function that converts a
bytes buffer of the dirstate file into the `DirstateMap` data structure as
used by the status algorithm. A single run each, collected by running
`hg status` this environment variable:
RUST_LOG=hg::dirstate::dirstate_map=trace,hg::dirstate_tree::dirstate_map=trace
Benchmark 1: Rust flat DirstateMap → Rust tree DirstateMap
hg status
mozilla-clean 562.3 ms ± 2.0 ms → 462.5 ms ± 0.6 ms 1.22 ± 0.00 times faster
mozilla-dirty 859.6 ms ± 2.2 ms → 719.5 ms ± 3.2 ms 1.19 ± 0.01 times faster
mozilla-ignored 558.2 ms ± 3.0 ms → 457.9 ms ± 2.9 ms 1.22 ± 0.01 times faster
mozilla-unknowns 859.4 ms ± 5.7 ms → 716.0 ms ± 4.7 ms 1.20 ± 0.01 times faster
netbeans-clean 336.5 ms ± 0.9 ms → 339.5 ms ± 0.4 ms 0.99 ± 0.00 times faster
netbeans-dirty 491.4 ms ± 1.6 ms → 475.1 ms ± 1.2 ms 1.03 ± 0.00 times faster
netbeans-ignored 343.7 ms ± 1.0 ms → 347.8 ms ± 0.4 ms 0.99 ± 0.00 times faster
netbeans-unknowns 484.3 ms ± 1.0 ms → 466.0 ms ± 1.2 ms 1.04 ± 0.00 times faster
hg status -mard
mozilla-clean 317.3 ms ± 0.6 ms → 422.5 ms ± 1.2 ms 0.75 ± 0.00 times faster
mozilla-dirty 315.4 ms ± 0.6 ms → 417.7 ms ± 1.1 ms 0.76 ± 0.00 times faster
mozilla-ignored 314.6 ms ± 0.6 ms → 417.4 ms ± 1.0 ms 0.75 ± 0.00 times faster
mozilla-unknowns 312.9 ms ± 0.9 ms → 417.3 ms ± 1.6 ms 0.75 ± 0.00 times faster
netbeans-clean 212.0 ms ± 0.6 ms → 283.6 ms ± 0.8 ms 0.75 ± 0.00 times faster
netbeans-dirty 211.4 ms ± 1.0 ms → 283.4 ms ± 1.6 ms 0.75 ± 0.01 times faster
netbeans-ignored 211.4 ms ± 0.9 ms → 283.9 ms ± 0.8 ms 0.74 ± 0.01 times faster
netbeans-unknowns 211.1 ms ± 0.6 ms → 283.4 ms ± 1.0 ms 0.74 ± 0.00 times faster
Parsing
mozilla-clean 38.4ms → 177.6ms
mozilla-dirty 38.8ms → 177.0ms
mozilla-ignored 38.8ms → 178.0ms
mozilla-unknowns 38.7ms → 176.9ms
netbeans-clean 16.5ms → 97.3ms
netbeans-dirty 16.5ms → 98.4ms
netbeans-ignored 16.9ms → 97.4ms
netbeans-unknowns 16.9ms → 96.3ms
Benchmark 2: Python + C dirstatemap → Rust tree DirstateMap
hg status
mozilla-clean 1261.0 ms ± 3.6 ms → 461.1 ms ± 0.5 ms 2.73 ± 0.00 times faster
mozilla-dirty 2293.4 ms ± 9.1 ms → 719.6 ms ± 3.6 ms 3.19 ± 0.01 times faster
mozilla-ignored 1240.4 ms ± 2.3 ms → 457.7 ms ± 1.9 ms 2.71 ± 0.00 times faster
mozilla-unknowns 2283.3 ms ± 9.0 ms → 719.7 ms ± 3.8 ms 3.17 ± 0.01 times faster
netbeans-clean 879.7 ms ± 3.5 ms → 339.9 ms ± 0.5 ms 2.59 ± 0.00 times faster
netbeans-dirty 1257.3 ms ± 4.7 ms → 474.6 ms ± 1.6 ms 2.65 ± 0.01 times faster
netbeans-ignored 943.9 ms ± 1.9 ms → 347.3 ms ± 1.1 ms 2.72 ± 0.00 times faster
netbeans-unknowns 1188.1 ms ± 5.0 ms → 465.2 ms ± 2.3 ms 2.55 ± 0.01 times faster
hg status -mard
mozilla-clean 903.2 ms ± 3.6 ms → 423.4 ms ± 2.2 ms 2.13 ± 0.01 times faster
mozilla-dirty 884.6 ms ± 4.5 ms → 417.3 ms ± 1.4 ms 2.12 ± 0.01 times faster
mozilla-ignored 881.9 ms ± 1.3 ms → 417.3 ms ± 0.8 ms 2.11 ± 0.00 times faster
mozilla-unknowns 878.5 ms ± 1.9 ms → 416.4 ms ± 0.9 ms 2.11 ± 0.00 times faster
netbeans-clean 434.9 ms ± 1.8 ms → 284.0 ms ± 0.8 ms 1.53 ± 0.01 times faster
netbeans-dirty 434.1 ms ± 0.8 ms → 283.1 ms ± 0.8 ms 1.53 ± 0.00 times faster
netbeans-ignored 431.7 ms ± 1.1 ms → 283.6 ms ± 1.8 ms 1.52 ± 0.01 times faster
netbeans-unknowns 433.0 ms ± 1.3 ms → 283.5 ms ± 0.7 ms 1.53 ± 0.00 times faster
Differential Revision: https://phab.mercurial-scm.org/D11516
;;; mq.el --- Emacs support for Mercurial Queues
;; Copyright (C) 2006 Bryan O'Sullivan
;; Author: Bryan O'Sullivan <bos@serpentine.com>
;; mq.el is free software; you can redistribute it and/or modify it
;; under the terms of the GNU General Public License version 2 or any
;; later version.
;; mq.el 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 mq.el, GNU Emacs, or XEmacs; see the file COPYING (`C-h
;; C-l'). If not, see <http://www.gnu.org/licenses/>.
(eval-when-compile (require 'cl))
(require 'mercurial)
(defcustom mq-mode-hook nil
"Hook run when a buffer enters mq-mode."
:type 'sexp
:group 'mercurial)
(defcustom mq-global-prefix "\C-cq"
"The global prefix for Mercurial Queues keymap bindings."
:type 'sexp
:group 'mercurial)
(defcustom mq-edit-mode-hook nil
"Hook run after a buffer is populated to edit a patch description."
:type 'sexp
:group 'mercurial)
(defcustom mq-edit-finish-hook nil
"Hook run before a patch description is finished up with."
:type 'sexp
:group 'mercurial)
(defcustom mq-signoff-address nil
"Address with which to sign off on a patch."
:type 'string
:group 'mercurial)
;;; Internal variables.
(defvar mq-mode nil
"Is this file managed by MQ?")
(make-variable-buffer-local 'mq-mode)
(put 'mq-mode 'permanent-local t)
(defvar mq-patch-history nil)
(defvar mq-top-patch '(nil))
(defvar mq-prev-buffer nil)
(make-variable-buffer-local 'mq-prev-buffer)
(put 'mq-prev-buffer 'permanent-local t)
(defvar mq-top nil)
(make-variable-buffer-local 'mq-top)
(put 'mq-top 'permanent-local t)
;;; Global keymap.
(defvar mq-global-map
(let ((map (make-sparse-keymap)))
(define-key map "." 'mq-push)
(define-key map ">" 'mq-push-all)
(define-key map "," 'mq-pop)
(define-key map "<" 'mq-pop-all)
(define-key map "=" 'mq-diff)
(define-key map "r" 'mq-refresh)
(define-key map "e" 'mq-refresh-edit)
(define-key map "i" 'mq-new)
(define-key map "n" 'mq-next)
(define-key map "o" 'mq-signoff)
(define-key map "p" 'mq-previous)
(define-key map "s" 'mq-edit-series)
(define-key map "t" 'mq-top)
map))
(global-set-key mq-global-prefix mq-global-map)
(add-minor-mode 'mq-mode 'mq-mode)
;;; Refresh edit mode keymap.
(defvar mq-edit-mode-map
(let ((map (make-sparse-keymap)))
(define-key map "\C-c\C-c" 'mq-edit-finish)
(define-key map "\C-c\C-k" 'mq-edit-kill)
(define-key map "\C-c\C-s" 'mq-signoff)
map))
;;; Helper functions.
(defun mq-read-patch-name (&optional source prompt force)
"Read a patch name to use with a command.
May return nil, meaning \"use the default\"."
(let ((patches (split-string
(hg-chomp (hg-run0 (or source "qseries"))) "\n")))
(when force
(completing-read (format "Patch%s: " (or prompt ""))
(mapcar (lambda (x) (cons x x)) patches)
nil
nil
nil
'mq-patch-history))))
(defun mq-refresh-buffers (root)
(save-excursion
(dolist (buf (hg-buffers-visiting-repo root))
(when (not (verify-visited-file-modtime buf))
(set-buffer buf)
(let ((ctx (hg-buffer-context)))
(message "Refreshing %s..." (buffer-name))
(revert-buffer t t t)
(hg-restore-context ctx)
(message "Refreshing %s...done" (buffer-name))))))
(hg-update-mode-lines root)
(mq-update-mode-lines root))
(defun mq-last-line ()
(goto-char (point-max))
(beginning-of-line)
(when (looking-at "^$")
(forward-line -1))
(let ((bol (point)))
(end-of-line)
(let ((line (buffer-substring bol (point))))
(when (> (length line) 0)
line))))
(defun mq-push (&optional patch)
"Push patches until PATCH is reached.
If PATCH is nil, push at most one patch."
(interactive (list (mq-read-patch-name "qunapplied" " to push"
current-prefix-arg)))
(let ((root (hg-root))
(prev-buf (current-buffer))
last-line ok)
(unless root
(error "Cannot push outside a repository!"))
(hg-sync-buffers root)
(let ((buf-name (format "MQ: Push %s" (or patch "next patch"))))
(kill-buffer (get-buffer-create buf-name))
(split-window-vertically)
(other-window 1)
(switch-to-buffer (get-buffer-create buf-name))
(cd root)
(message "Pushing...")
(setq ok (= 0 (apply 'call-process (hg-binary) nil t t "qpush"
(if patch (list patch))))
last-line (mq-last-line))
(let ((lines (count-lines (point-min) (point-max))))
(if (or (<= lines 1)
(and (equal lines 2) (string-match "Now at:" last-line)))
(progn
(kill-buffer (current-buffer))
(delete-window))
(hg-view-mode prev-buf))))
(mq-refresh-buffers root)
(sit-for 0)
(when last-line
(if ok
(message "Pushing... %s" last-line)
(error "Pushing... %s" last-line)))))
(defun mq-push-all ()
"Push patches until all are applied."
(interactive)
(mq-push "-a"))
(defun mq-pop (&optional patch)
"Pop patches until PATCH is reached.
If PATCH is nil, pop at most one patch."
(interactive (list (mq-read-patch-name "qapplied" " to pop to"
current-prefix-arg)))
(let ((root (hg-root))
last-line ok)
(unless root
(error "Cannot pop outside a repository!"))
(hg-sync-buffers root)
(set-buffer (generate-new-buffer "qpop"))
(cd root)
(message "Popping...")
(setq ok (= 0 (apply 'call-process (hg-binary) nil t t "qpop"
(if patch (list patch))))
last-line (mq-last-line))
(kill-buffer (current-buffer))
(mq-refresh-buffers root)
(sit-for 0)
(when last-line
(if ok
(message "Popping... %s" last-line)
(error "Popping... %s" last-line)))))
(defun mq-pop-all ()
"Push patches until none are applied."
(interactive)
(mq-pop "-a"))
(defun mq-refresh-internal (root &rest args)
(hg-sync-buffers root)
(let ((patch (mq-patch-info "qtop")))
(message "Refreshing %s..." patch)
(let ((ret (apply 'hg-run "qrefresh" args)))
(if (equal (car ret) 0)
(message "Refreshing %s... done." patch)
(error "Refreshing %s... %s" patch (hg-chomp (cdr ret)))))))
(defun mq-refresh (&optional git)
"Refresh the topmost applied patch.
With a prefix argument, generate a git-compatible patch."
(interactive "P")
(let ((root (hg-root)))
(unless root
(error "Cannot refresh outside of a repository!"))
(apply 'mq-refresh-internal root (if git '("--git")))))
(defun mq-patch-info (cmd &optional msg)
(let* ((ret (hg-run cmd))
(info (hg-chomp (cdr ret))))
(if (equal (car ret) 0)
(if msg
(message "%s patch: %s" msg info)
info)
(error "%s" info))))
(defun mq-top ()
"Print the name of the topmost applied patch."
(interactive)
(mq-patch-info "qtop" "Top"))
(defun mq-next ()
"Print the name of the next patch to be pushed."
(interactive)
(mq-patch-info "qnext" "Next"))
(defun mq-previous ()
"Print the name of the first patch below the topmost applied patch.
This would become the active patch if popped to."
(interactive)
(mq-patch-info "qprev" "Previous"))
(defun mq-edit-finish ()
"Finish editing the description of this patch, and refresh the patch."
(interactive)
(unless (equal (mq-patch-info "qtop") mq-top)
(error "Topmost patch has changed!"))
(hg-sync-buffers hg-root)
(run-hooks 'mq-edit-finish-hook)
(mq-refresh-internal hg-root "-m" (buffer-substring (point-min) (point-max)))
(let ((buf mq-prev-buffer))
(kill-buffer nil)
(switch-to-buffer buf)))
(defun mq-edit-kill ()
"Kill the edit currently being prepared."
(interactive)
(when (or (not (buffer-modified-p)) (y-or-n-p "Really kill this edit? "))
(let ((buf mq-prev-buffer))
(kill-buffer nil)
(switch-to-buffer buf))))
(defun mq-get-top (root)
(let ((entry (assoc root mq-top-patch)))
(if entry
(cdr entry))))
(defun mq-set-top (root patch)
(let ((entry (assoc root mq-top-patch)))
(if entry
(if patch
(setcdr entry patch)
(setq mq-top-patch (delq entry mq-top-patch)))
(setq mq-top-patch (cons (cons root patch) mq-top-patch)))))
(defun mq-update-mode-lines (root)
(let ((cwd default-directory))
(cd root)
(condition-case nil
(mq-set-top root (mq-patch-info "qtop"))
(error (mq-set-top root nil)))
(cd cwd))
(let ((patch (mq-get-top root)))
(save-excursion
(dolist (buf (hg-buffers-visiting-repo root))
(set-buffer buf)
(if mq-mode
(setq mq-mode (or (and patch (concat " MQ:" patch)) " MQ")))))))
(defun mq-mode (&optional arg)
"Minor mode for Mercurial repositories with an MQ patch queue"
(interactive "i")
(cond ((hg-root)
(setq mq-mode (if (null arg) (not mq-mode)
arg))
(mq-update-mode-lines (hg-root))))
(run-hooks 'mq-mode-hook))
(defun mq-edit-mode ()
"Mode for editing the description of a patch.
Key bindings
------------
\\[mq-edit-finish] use this description
\\[mq-edit-kill] abandon this description"
(interactive)
(use-local-map mq-edit-mode-map)
(set-syntax-table text-mode-syntax-table)
(setq local-abbrev-table text-mode-abbrev-table
major-mode 'mq-edit-mode
mode-name "MQ-Edit")
(set-buffer-modified-p nil)
(setq buffer-undo-list nil)
(run-hooks 'text-mode-hook 'mq-edit-mode-hook))
(defun mq-refresh-edit ()
"Refresh the topmost applied patch, editing the patch description."
(interactive)
(while mq-prev-buffer
(set-buffer mq-prev-buffer))
(let ((root (hg-root))
(prev-buffer (current-buffer))
(patch (mq-patch-info "qtop")))
(hg-sync-buffers root)
(let ((buf-name (format "*MQ: Edit description of %s*" patch)))
(switch-to-buffer (get-buffer-create buf-name))
(when (= (point-min) (point-max))
(set (make-local-variable 'hg-root) root)
(set (make-local-variable 'mq-top) patch)
(setq mq-prev-buffer prev-buffer)
(insert (hg-run0 "qheader"))
(goto-char (point-min)))
(mq-edit-mode)
(cd root)))
(message "Type `C-c C-c' to finish editing and refresh the patch."))
(defun mq-new (name)
"Create a new empty patch named NAME.
The patch is applied on top of the current topmost patch.
With a prefix argument, forcibly create the patch even if the working
directory is modified."
(interactive (list (mq-read-patch-name "qseries" " to create" t)))
(message "Creating patch...")
(let ((ret (if current-prefix-arg
(hg-run "qnew" "-f" name)
(hg-run "qnew" name))))
(if (equal (car ret) 0)
(progn
(hg-update-mode-lines (buffer-file-name))
(message "Creating patch... done."))
(error "Creating patch... %s" (hg-chomp (cdr ret))))))
(defun mq-edit-series ()
"Edit the MQ series file directly."
(interactive)
(let ((root (hg-root)))
(unless root
(error "Not in an MQ repository!"))
(find-file (concat root ".hg/patches/series"))))
(defun mq-diff (&optional git)
"Display a diff of the topmost applied patch.
With a prefix argument, display a git-compatible diff."
(interactive "P")
(hg-view-output ((format "MQ: Diff of %s" (mq-patch-info "qtop")))
(if git
(call-process (hg-binary) nil t nil "qdiff" "--git")
(call-process (hg-binary) nil t nil "qdiff"))
(diff-mode)
(font-lock-fontify-buffer)))
(defun mq-signoff ()
"Sign off on the current patch, in the style used by the Linux kernel.
If the variable mq-signoff-address is non-nil, it will be used, otherwise
the value of the ui.username item from your hgrc will be used."
(interactive)
(let ((was-editing (eq major-mode 'mq-edit-mode))
signed)
(unless was-editing
(mq-refresh-edit))
(save-excursion
(let* ((user (or mq-signoff-address
(hg-run0 "debugconfig" "ui.username")))
(signoff (concat "Signed-off-by: " user)))
(if (search-forward signoff nil t)
(message "You have already signed off on this patch.")
(goto-char (point-max))
(let ((case-fold-search t))
(if (re-search-backward "^Signed-off-by: " nil t)
(forward-line 1)
(insert "\n")))
(insert signoff)
(message "%s" signoff)
(setq signed t))))
(unless was-editing
(if signed
(mq-edit-finish)
(mq-edit-kill)))))
(provide 'mq)
;;; Local Variables:
;;; prompt-to-byte-compile: nil
;;; end: