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changegroup: introduce requests to define delta generation...
changegroup: introduce requests to define delta generation Currently, we iterate through each revision we will be producing a delta for then call into 1 of 2 functions for generating that delta. Deltas are emitted as we iterate. A problem with this model is that revision generation is tightly coupled to the changegroup code. And the storage layer needs to expose APIs like deltaparent() so changegroup delta generation can produce a delta with that knowledge. Another problem is that in this model, deltas can only be produced sequentially after the previous delta was produced and emitted. Some storage backends might be capable of producing deltas in parallel (e.g. if the changegroup deltas are cached somewhere). This commit aims to solve these problems by turning delta generation into a 2 phase implementation where the first phase determines info about all the deltas that need to be generated and the 2nd phase resolves those deltas. We introduce a "revisiondeltarequest" object that holds data about a to-be-generated delta. We perform a full pass over all revisions whose delta is to be generated and generate a "revisiondeltarequest" for each. Then we iterate over the "revisiondeltarequest" instances and derive a "revisiondelta" for each. This patch was quite large. In order to avoid even more churn, aspects of the implementation are less than ideal. e.g. we're recording revision numbers instead of nodes in a few places and we don't yet have a formal API for resolving an iterable of revisiondeltarequest instances. Things will be improved in subsequent commits. Unfortunately, this commit reduces performance substantially. For `hg perfchangegroupchangelog` on my hg repo: ! wall 1.512607 comb 1.510000 user 1.490000 sys 0.020000 (best of 7) ! wall 2.150863 comb 2.150000 user 2.150000 sys 0.000000 (best of 5) And for `hg bundle -t none-v2 -a` for the mozilla-unified repo: 178.32user 4.22system 3:02.59elapsed 190.97user 4.17system 3:15.19elapsed Some of this was attributed to changelog slowdown. `hg perfchangegroupchangelog` on mozilla-unified: ! wall 21.688715 comb 21.690000 user 21.570000 sys 0.120000 (best of 3) ! wall 25.683659 comb 25.680000 user 25.540000 sys 0.140000 (best of 3) Profiling seems to reveal that the changelog slowdown is due to reading changelog revisions multiple times. First in the linknode callback to resolve the set of files changed. Second in the delta generation. Before, we likely had hit the last revision cache in the revlog when doing delta generation since we performed that immediately after performing the linknode callback. I'm not exactly sure where the other ~8s are being spent. It might be from overhead of constructing a few million revisiondeltarequest objects. I'm OK with the regression for now because it is in service of a larger cause (storage abstraction). I'll try to profile later and claw back the performance. Differential Revision: https://phab.mercurial-scm.org/D4215
Gregory Szorc -
r39054:e793e11e default
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Mercurial for Windows



Welcome to Mercurial for Windows!




Mercurial is a command-line application. You must run it from
the Windows command prompt (or if you're hard core, a <a<br /> href="http://www.mingw.org/">MinGW shell).




Note: the standard http://www.mingw.org/">MinGW
msys startup script uses rxvt which has problems setting up
standard input and output. Running bash directly works
correctly.




For documentation, please visit the <a<br /> href="https://mercurial-scm.org/">Mercurial web site.
You can also download a free book, <a<br /> href="https://book.mercurial-scm.org/">Mercurial: The Definitive
Guide.




By default, Mercurial installs to C:\Program
Files\Mercurial
. The Mercurial command is called
hg.exe.



Testing Mercurial after you've installed it




The easiest way to check that Mercurial is installed properly is
to just type the following at the command prompt:




hg



This command should print a useful help message. If it does,
other Mercurial commands should work fine for you.



Configuration notes


Default editor



The default editor for commit messages is 'notepad'. You can set
the EDITOR (or HGEDITOR) environment variable
to specify your preference or set it in mercurial.ini:



[ui]
editor = whatever


Configuring a Merge program



It should be emphasized that Mercurial by itself doesn't attempt
to do a Merge at the file level, neither does it make any
attempt to Resolve the conflicts.




By default, Mercurial will use the merge program defined by the
HGMERGE environment variable, or uses the one defined
in the mercurial.ini file. (see <a<br /> href="https://mercurial-scm.org/wiki/MergeProgram">MergeProgram
on the Mercurial Wiki for more information)



Reporting problems




Before you report any problems, please consult the <a<br /> href="https://mercurial-scm.org/">Mercurial web site
and see if your question is already in our list of <a<br /> href="https://mercurial-scm.org/wiki/FAQ">Frequently
Answered Questions (the "FAQ").




If you cannot find an answer to your question, please feel free
to send mail to the Mercurial mailing list, at <a<br /> href="mailto:mercurial@mercurial-scm.org">mercurial@mercurial-scm.org.
Remember, the more useful information you include in your
report, the easier it will be for us to help you!




If you are IRC-savvy, that's usually the fastest way to get
help. Go to #mercurial on irc.freenode.net.



Author and copyright information




Mercurial was written by http://www.selenic.com">Matt
Mackall, and is maintained by Matt and a team of volunteers.




The Windows installer was written by <a<br /> href="http://www.serpentine.com/blog">Bryan O'Sullivan.




Mercurial is Copyright 2005-2018 Matt Mackall and others. See
the Contributors.txt file for a list of contributors.




Mercurial is free software; you can redistribute it and/or
modify it under the terms of the <a<br /> href="http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt">GNU
General Public License version 2 or any later version.




Mercurial 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.


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