view contrib/chg/chg.1 @ 47120:7109a38830c9

dirstate-tree: Fold "tracked descendants" counter update in main walk

For the purpose of implementing `has_tracked_dir` (which means "has tracked
descendants) without an expensive sub-tree traversal, we maintaing a counter
of tracked descendants on each "directory" node of the tree-shaped dirstate.

Before this changeset, mutating or inserting a node at a given path would
involve:

* Walking the tree from root through ancestors to find the node or the spot
  where to insert it
* Looking at the previous node if any to decide what counter update is needed
* Performing any node mutation
* Walking the tree *again* to update counters in ancestor nodes

When profiling `hg status` on a large repo, this second walk takes times
while loading a the dirstate from disk.

It turns out we have enough information to decide before he first tree walk
what counter update is needed. This changeset merges the two walks, gaining
~10% of the total time for `hg update` (in the same hyperfine benchmark as
the previous changeset).

---

Profiling was done by compiling with this `.cargo/config`:

    [profile.release]
    debug = true

then running with:

    py-spy record -r 500 -n -o /tmp/hg.json --format speedscope -- \
    ./hg status -R $REPO --config experimental.dirstate-tree.in-memory=1

then visualizing the recorded JSON file in https://www.speedscope.app/

Differential Revision: https://phab.mercurial-scm.org/D10554

.\"                                      Hey, EMACS: -*- nroff -*-
.\" First parameter, NAME, should be all caps
.\" Second parameter, SECTION, should be 1-8, maybe w/ subsection
.\" other parameters are allowed: see man(7), man(1)
.TH CHG 1 "March 3, 2013"
.\" Please adjust this date whenever revising the manpage.
.\"
.\" Some roff macros, for reference:
.\" .nh        disable hyphenation
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.\" .ad b      justify to both left and right margins
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.\" for manpage-specific macros, see man(7)
.SH NAME
chg \- a fast client for Mercurial command server
.SH SYNOPSIS
.B chg
.IR command " [" options "] [" arguments "]..."
.br
.SH DESCRIPTION
The
.B chg
command is the wrapper for
.B hg
command.
It uses the Mercurial command server to reduce start-up overhead.
.SH OPTIONS
This program accepts the same command line syntax as the
.B hg
command. Additionally it accepts the following options.
.TP
.B \-\-kill\-chg\-daemon
Terminate the background command servers.
.SH SEE ALSO
.BR hg (1)
.SH AUTHOR
Written by Yuya Nishihara <[e-mail]>.