Mercurial > hg
view tests/test-show.t @ 38732:be4984261611
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
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 18 Jul 2018 09:49:34 -0700 |
parents | e6b5e7329ff2 |
children |
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$ cat >> $HGRCPATH << EOF > [extensions] > show = > EOF No arguments shows available views $ hg init empty $ cd empty $ hg show available views: bookmarks -- bookmarks and their associated changeset stack -- current line of work work -- changesets that aren't finished abort: no view requested (use "hg show VIEW" to choose a view) [255] `hg help show` prints available views $ hg help show hg show VIEW show various repository information A requested view of repository data is displayed. If no view is requested, the list of available views is shown and the command aborts. Note: There are no backwards compatibility guarantees for the output of this command. Output may change in any future Mercurial release. Consumers wanting stable command output should specify a template via "-T/--template". List of available views: bookmarks bookmarks and their associated changeset stack current line of work work changesets that aren't finished (use 'hg help -e show' to show help for the show extension) options: -T --template TEMPLATE display with template (some details hidden, use --verbose to show complete help) Unknown view prints error $ hg show badview abort: unknown view: badview (run "hg show" to see available views) [255] HGPLAIN results in abort $ HGPLAIN=1 hg show bookmarks abort: must specify a template in plain mode (invoke with -T/--template to control output format) [255] But not if a template is specified $ HGPLAIN=1 hg show bookmarks -T '{bookmark}\n' (no bookmarks set) $ cd .. bookmarks view with no bookmarks prints empty message $ hg init books $ cd books $ touch f0 $ hg -q commit -A -m initial $ hg show bookmarks (no bookmarks set) bookmarks view shows bookmarks in an aligned table $ echo book1 > f0 $ hg commit -m 'commit for book1' $ echo book2 > f0 $ hg commit -m 'commit for book2' $ hg bookmark -r 1 book1 $ hg bookmark a-longer-bookmark $ hg show bookmarks * a-longer-bookmark 7b57 book1 b757 A custom bookmarks template works $ hg show bookmarks -T '{node} {bookmark} {active}\n' 7b5709ab64cbc34da9b4367b64afff47f2c4ee83 a-longer-bookmark True b757f780b8ffd71267c6ccb32e0882d9d32a8cc0 book1 False bookmarks JSON works $ hg show bookmarks -T json [ { "active": true, "bookmark": "a-longer-bookmark", "longestbookmarklen": 17, "node": "7b5709ab64cbc34da9b4367b64afff47f2c4ee83", "nodelen": 4 }, { "active": false, "bookmark": "book1", "longestbookmarklen": 17, "node": "b757f780b8ffd71267c6ccb32e0882d9d32a8cc0", "nodelen": 4 } ] JSON works with no bookmarks $ hg book -d a-longer-bookmark $ hg book -d book1 $ hg show bookmarks -T json [ ] commands.show.aliasprefix aliases values to `show <view>` $ hg --config commands.show.aliasprefix=s sbookmarks (no bookmarks set) $ hg --config commands.show.aliasprefix=sh shwork @ 7b57 commit for book2 o b757 commit for book1 o ba59 initial $ hg --config commands.show.aliasprefix='s sh' swork @ 7b57 commit for book2 o b757 commit for book1 o ba59 initial $ hg --config commands.show.aliasprefix='s sh' shwork @ 7b57 commit for book2 o b757 commit for book1 o ba59 initial The aliases don't appear in `hg config` $ hg --config commands.show.aliasprefix=s config alias [1] Doesn't overwrite existing alias $ hg --config alias.swork='log -r .' --config commands.show.aliasprefix=s swork changeset: 2:7b5709ab64cb tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: commit for book2 $ hg --config alias.swork='log -r .' --config commands.show.aliasprefix=s config alias alias.swork=log -r . $ cd ..