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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
Pulkit Goyal - - Load All Authors

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Pulkit Goyal
thirdparty: vendor cbor2 python library...
 r37144 .. image:: https://travis-ci.org/agronholm/cbor2.svg?branch=master
:target: https://travis-ci.org/agronholm/cbor2
:alt: Build Status
.. image:: https://coveralls.io/repos/github/agronholm/cbor2/badge.svg?branch=master
:target: https://coveralls.io/github/agronholm/cbor2?branch=master
:alt: Code Coverage
This library provides encoding and decoding for the Concise Binary Object Representation (CBOR)
(`RFC 7049`_) serialization format.
There exists another Python CBOR implementation (cbor) which is faster on CPython due to its C
extensions. On PyPy, cbor2 and cbor are almost identical in performance. The other implementation
also lacks documentation and a comprehensive test suite, does not support most standard extension
tags and is known to crash (segfault) when passed a cyclic structure (say, a list containing
itself).
.. _RFC 7049: https://tools.ietf.org/html/rfc7049
Project links
-------------
* `Documentation <http://cbor2.readthedocs.org/>`_
* `Source code <https://github.com/agronholm/cbor2>`_
* `Issue tracker <https://github.com/agronholm/cbor2/issues>`_