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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
Robert Bachmann - - Load All Authors

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xml.rnc
41 lines | 1.2 KiB | application/relax-ng-compact-syntax | RNCCompactLexer
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# RelaxNG schema for "xml" log style
# Inspired by Subversion's XML log format.
start = log
node.type = xsd:string {minLength = "40" maxLength = "40"}
log = element log { logentry+ }
logentry = element logentry {
logentry.attlist,
branch*, tag*, hgparent*,
author, date,
msg, paths?, copies?, extra*
}
logentry.attlist =
attribute revision {xsd:nonNegativeInteger}
& attribute node {node.type}
branch = element branch { text }
tag = element tag { text }
hgparent = element parent {hgparent.attlist, text}
hgparent.attlist =
attribute revision {xsd:integer {minInclusive = "-1"} }
& attribute node {node.type}
author = element author { author.attlist, text }
author.attlist =
attribute email {text}
date = element date {xsd:dateTime}
msg = element msg {msg.attlist, text}
msg.attlist =
attribute xml:space {"preserve"}
paths = element paths { path* }
path = element path { path.attlist, text }
path.attlist =
# Action: (A)dd, (M)odify, (R)emove
attribute action {"A"|"M"|"R"}
copies = element copies { copy+ }
copy = element copy { copy.attlist, text }
copy.attlist =
attribute source {text}
extra = element extra {extra.attlist, text}
extra.attlist =
attribute key {text}