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merge: mark file gets as not thread safe (issue5933)...
merge: mark file gets as not thread safe (issue5933) In default installs, this has the effect of disabling the thread-based worker on Windows when manifesting files in the working directory. My measurements have shown that with revlog-based repositories, Mercurial spends a lot of CPU time in revlog code resolving file data. This ends up incurring a lot of context switching across threads and slows down `hg update` operations when going from an empty working directory to the tip of the repo. On mozilla-unified (246,351 files) on an i7-6700K (4+4 CPUs): before: 487s wall after: 360s wall (equivalent to worker.enabled=false) cpus=2: 379s wall Even with only 2 threads, the thread pool is still slower. The introduction of the thread-based worker (02b36e860e0b) states that it resulted in a "~50%" speedup for `hg sparse --enable-profile` and `hg sparse --disable-profile`. This disagrees with my measurement above. I theorize a few reasons for this: 1) Removal of files from the working directory is I/O - not CPU - bound and should benefit from a thread pool (unless I/O is insanely fast and the GIL release is near instantaneous). So tests like `hg sparse --enable-profile` may exercise deletion throughput and aren't good benchmarks for worker tasks that are CPU heavy. 2) The patch was authored by someone at Facebook. The results were likely measured against a repository using remotefilelog. And I believe that revision retrieval during working directory updates with remotefilelog will often use a remote store, thus being I/O and not CPU bound. This probably resulted in an overstated performance gain. Since there appears to be a need to enable the thread-based worker with some stores, I've made the flagging of file gets as thread safe configurable. I've made it experimental because I don't want to formalize a boolean flag for this option and because this attribute is best captured against the store implementation. But we don't have a proper store API for this yet. I'd rather cross this bridge later. It is possible there are revlog-based repositories that do benefit from a thread-based worker. I didn't do very comprehensive testing. If there are, we may want to devise a more proper algorithm for whether to use the thread-based worker, including possibly config options to limit the number of threads to use. But until I see evidence that justifies complexity, simplicity wins. Differential Revision: https://phab.mercurial-scm.org/D3963
Matt Mackall - - Load All Authors

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hg-test-mode.el
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;; hg-test-mode.el - Major mode for editing Mercurial tests
;;
;; Copyright 2014 Matt Mackall <mpm@selenic.com>
;; "I have no idea what I'm doing"
;;
;; This software may be used and distributed according to the terms of the
;; GNU General Public License version 2 or any later version.
;;
;; To enable, add something like the following to your .emacs:
;;
;; (if (file-exists-p "~/hg/contrib/hg-test-mode.el")
;; (load "~/hg/contrib/hg-test-mode.el"))
(defvar hg-test-mode-hook nil)
(defvar hg-test-mode-map
(let ((map (make-keymap)))
(define-key map "\C-j" 'newline-and-indent)
map)
"Keymap for hg test major mode")
(add-to-list 'auto-mode-alist '("\\.t\\'" . hg-test-mode))
(defconst hg-test-font-lock-keywords-1
(list
'("^ \\(\\$\\|>>>\\) " 1 font-lock-builtin-face)
'("^ \\(>\\|\\.\\.\\.\\) " 1 font-lock-constant-face)
'("^ \\([[][0-9]+[]]\\)$" 1 font-lock-warning-face)
'("^ \\(.*?\\)\\(\\( [(][-a-z]+[)]\\)*\\)$" 1 font-lock-string-face)
'("\\$?\\(HG\\|TEST\\)\\w+=?" . font-lock-variable-name-face)
'("^ \\(.*?\\)\\(\\( [(][-a-z]+[)]\\)+\\)$" 2 font-lock-type-face)
'("^#.*" . font-lock-preprocessor-face)
'("^\\([^ ].*\\)$" 1 font-lock-comment-face)
)
"Minimal highlighting expressions for hg-test mode")
(defvar hg-test-font-lock-keywords hg-test-font-lock-keywords-1
"Default highlighting expressions for hg-test mode")
(defvar hg-test-mode-syntax-table
(let ((st (make-syntax-table)))
(modify-syntax-entry ?\" "w" st) ;; disable standard quoting
st)
"Syntax table for hg-test mode")
(defun hg-test-mode ()
(interactive)
(kill-all-local-variables)
(use-local-map hg-test-mode-map)
(set-syntax-table hg-test-mode-syntax-table)
(set (make-local-variable 'font-lock-defaults) '(hg-test-font-lock-keywords))
(setq major-mode 'hg-test-mode)
(setq mode-name "hg-test")
(run-hooks 'hg-test-mode-hook))
(provide 'hg-test-mode)