Mercurial > hg
view tests/test-double-merge.t @ 30212:260af19891f2
changegroup: increase write buffer size to 128k
By default, Python defers to the operating system for choosing the
default buffer size on opened files. On my Linux machine, the default
is 4k, which is really small for 2016.
This patch bumps the write buffer size when writing
changegroups/bundles to 128k. This matches the 128k read buffer
we already use on revlogs.
It's worth noting that this only impacts when writing to an explicit
file (such as during `hg bundle`). Buffers when writing to bundle
files via the repo vfs or to a temporary file are not impacted.
When producing a none-v2 bundle file of the mozilla-unified repository,
this change caused the number of write() system calls to drop from
952,449 to 29,788. After this change, the most frequent system
calls are fstat(), read(), lseek(), and open(). There were
2,523,672 system calls after this patch (so a net decrease of
~950k is statistically significant).
This change shows no performance change on my system. But I have a
high-end system with a fast SSD. It is quite possible this change
will have a significant impact on network file systems, where
extra network round trips due to excessive I/O system calls could
introduce significant latency.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Sun, 16 Oct 2016 13:35:23 -0700 |
parents | 564a354f7f35 |
children | 91a0bc50b288 |
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$ hg init repo $ cd repo $ echo line 1 > foo $ hg ci -qAm 'add foo' copy foo to bar and change both files $ hg cp foo bar $ echo line 2-1 >> foo $ echo line 2-2 >> bar $ hg ci -m 'cp foo bar; change both' in another branch, change foo in a way that doesn't conflict with the other changes $ hg up -qC 0 $ echo line 0 > foo $ hg cat foo >> foo $ hg ci -m 'change foo' created new head we get conflicts that shouldn't be there $ hg merge -P changeset: 1:484bf6903104 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: cp foo bar; change both $ hg merge --debug searching for copies back to rev 1 unmatched files in other: bar all copies found (* = to merge, ! = divergent, % = renamed and deleted): src: 'foo' -> dst: 'bar' * checking for directory renames resolving manifests branchmerge: True, force: False, partial: False ancestor: e6dc8efe11cc, local: 6a0df1dad128+, remote: 484bf6903104 preserving foo for resolve of bar preserving foo for resolve of foo starting 4 threads for background file closing (?) bar: remote copied from foo -> m (premerge) picked tool ':merge' for bar (binary False symlink False changedelete False) merging foo and bar to bar my bar@6a0df1dad128+ other bar@484bf6903104 ancestor foo@e6dc8efe11cc premerge successful foo: versions differ -> m (premerge) picked tool ':merge' for foo (binary False symlink False changedelete False) merging foo my foo@6a0df1dad128+ other foo@484bf6903104 ancestor foo@e6dc8efe11cc premerge successful 0 files updated, 2 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) contents of foo $ cat foo line 0 line 1 line 2-1 contents of bar $ cat bar line 0 line 1 line 2-2 $ cd ..