Mercurial > hg
view tests/test-empty-group.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 | 301725c3df9a |
children | eb586ed5d8ce |
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# A B # # 3 4 3 # |\/| |\ # |/\| | \ # 1 2 1 2 # \ / \ / # 0 0 # # if the result of the merge of 1 and 2 # is the same in 3 and 4, no new manifest # will be created and the manifest group # will be empty during the pull # # (plus we test a failure where outgoing # wrongly reported the number of csets) $ hg init a $ cd a $ touch init $ hg ci -A -m 0 adding init $ touch x y $ hg ci -A -m 1 adding x adding y $ hg update 0 0 files updated, 0 files merged, 2 files removed, 0 files unresolved $ touch x y $ hg ci -A -m 2 adding x adding y created new head $ hg merge 1 0 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg ci -A -m m1 $ hg update -C 1 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg merge 2 0 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg ci -A -m m2 created new head $ cd .. $ hg clone -r 3 a b adding changesets adding manifests adding file changes added 4 changesets with 3 changes to 3 files updating to branch default 3 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg clone -r 4 a c adding changesets adding manifests adding file changes added 4 changesets with 3 changes to 3 files updating to branch default 3 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R a outgoing b comparing with b searching for changes changeset: 4:1ec3c74fc0e0 tag: tip parent: 1:79f9e10cd04e parent: 2:8e1bb01c1a24 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: m2 $ hg -R a outgoing c comparing with c searching for changes changeset: 3:d15a0c284984 parent: 2:8e1bb01c1a24 parent: 1:79f9e10cd04e user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: m1 $ hg -R b outgoing c comparing with c searching for changes changeset: 3:d15a0c284984 tag: tip parent: 2:8e1bb01c1a24 parent: 1:79f9e10cd04e user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: m1 $ hg -R c outgoing b comparing with b searching for changes changeset: 3:1ec3c74fc0e0 tag: tip parent: 1:79f9e10cd04e parent: 2:8e1bb01c1a24 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: m2 $ hg -R b pull a pulling from a searching for changes adding changesets adding manifests adding file changes added 1 changesets with 0 changes to 0 files (+1 heads) (run 'hg heads' to see heads, 'hg merge' to merge) $ hg -R c pull a pulling from a searching for changes adding changesets adding manifests adding file changes added 1 changesets with 0 changes to 0 files (+1 heads) (run 'hg heads' to see heads, 'hg merge' to merge)