Mercurial > hg
view mercurial/help/urls.txt @ 26379:39d643252b9f
revlog: use existing file handle when reading during _addrevision
_addrevision() may need to read from revlogs as part of computing
deltas. Previously, we would flush existing file handles and open
a new, short-lived file handle to perform the reading.
If we have an existing file handle, it seems logical to reuse it
for reading instead of opening a new file handle. This patch
makes that the new behavior.
After this patch, revlog files are only reopened when adding
revisions if the revlog is switched from inline to non-inline.
On Linux when unbundling a bundle of the mozilla-central repo, this
patch has the following impact on system call counts:
Call Before After Delta
write 827,639 673,390 -154,249
open 700,103 684,089 -16,014
read 74,489 74,489 0
fstat 493,924 461,896 -32,028
close 249,131 233,117 -16,014
stat 242,001 242,001 0
lstat 18,676 18,676 0
lseek 20,268 20,268 0
ioctl 14,652 13,173 -1,479
TOTAL 3,180,758 2,930,679 -250,079
It's worth noting that many of the open() calls fail due to missing
files. That's why there are many more open() calls than close().
Despite the significant system call reduction, this change does not
seem to have a significant performance impact on Linux.
On Windows 10 (not a VM, on a SSD), this patch appears to reduce
unbundle time for mozilla-central from ~960s to ~920s. This isn't
as significant as I was hoping. But a decrease it is nonetheless.
Still, Windows unbundle performance is still >2x slower than Linux.
Despite the lack of significant gains, fewer system calls is fewer
system calls. If nothing else, this will narrow the focus of potential
areas to optimize in the future.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Sun, 27 Sep 2015 16:08:18 -0700 |
parents | 01d68fb07915 |
children | 5da7b8cb6f75 |
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Valid URLs are of the form:: local/filesystem/path[#revision] file://local/filesystem/path[#revision] http://[user[:pass]@]host[:port]/[path][#revision] https://[user[:pass]@]host[:port]/[path][#revision] ssh://[user@]host[:port]/[path][#revision] Paths in the local filesystem can either point to Mercurial repositories or to bundle files (as created by :hg:`bundle` or :hg:`incoming --bundle`). See also :hg:`help paths`. An optional identifier after # indicates a particular branch, tag, or changeset to use from the remote repository. See also :hg:`help revisions`. Some features, such as pushing to http:// and https:// URLs are only possible if the feature is explicitly enabled on the remote Mercurial server. Note that the security of HTTPS URLs depends on proper configuration of web.cacerts. Some notes about using SSH with Mercurial: - SSH requires an accessible shell account on the destination machine and a copy of hg in the remote path or specified with as remotecmd. - path is relative to the remote user's home directory by default. Use an extra slash at the start of a path to specify an absolute path:: ssh://example.com//tmp/repository - Mercurial doesn't use its own compression via SSH; the right thing to do is to configure it in your ~/.ssh/config, e.g.:: Host *.mylocalnetwork.example.com Compression no Host * Compression yes Alternatively specify "ssh -C" as your ssh command in your configuration file or with the --ssh command line option. These URLs can all be stored in your configuration file with path aliases under the [paths] section like so:: [paths] alias1 = URL1 alias2 = URL2 ... You can then use the alias for any command that uses a URL (for example :hg:`pull alias1` will be treated as :hg:`pull URL1`). Two path aliases are special because they are used as defaults when you do not provide the URL to a command: default: When you create a repository with hg clone, the clone command saves the location of the source repository as the new repository's 'default' path. This is then used when you omit path from push- and pull-like commands (including incoming and outgoing). default-push: The push command will look for a path named 'default-push', and prefer it over 'default' if both are defined.