view tests/test-branch-option.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.

test branch selection options

  $ hg init branch
  $ cd branch
  $ hg branch a
  marked working directory as branch a
  (branches are permanent and global, did you want a bookmark?)
  $ echo a > foo
  $ hg ci -d '0 0' -Ama
  adding foo
  $ echo a2 > foo
  $ hg ci -d '0 0' -ma2
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg branch c
  marked working directory as branch c
  $ echo c > foo
  $ hg ci -d '0 0' -mc
  $ hg tag -l z
  $ cd ..
  $ hg clone -r 0 branch branch2
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  updating to branch a
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd branch2
  $ hg up 0
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg branch b
  marked working directory as branch b
  $ echo b > foo
  $ hg ci -d '0 0' -mb
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --encoding utf-8 branch æ
  marked working directory as branch \xc3\xa6 (esc)
  $ echo ae1 > foo
  $ hg ci -d '0 0' -mae1
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --encoding utf-8 branch -f æ
  marked working directory as branch \xc3\xa6 (esc)
  $ echo ae2 > foo
  $ hg ci -d '0 0' -mae2
  created new head
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg branch -f b
  marked working directory as branch b
  $ echo b2 > foo
  $ hg ci -d '0 0' -mb2
  created new head

unknown branch and fallback

  $ hg in -qbz
  abort: unknown branch 'z'!
  [255]
  $ hg in -q ../branch#z
  2:f25d57ab0566
  $ hg out -qbz
  abort: unknown branch 'z'!
  [255]

in rev c branch a

  $ hg in -qr c ../branch#a
  1:dd6e60a716c6
  2:f25d57ab0566
  $ hg in -qr c -b a
  1:dd6e60a716c6
  2:f25d57ab0566

out branch .

  $ hg out -q ../branch#.
  1:b84708d77ab7
  4:65511d0e2b55
  $ hg out -q -b .
  1:b84708d77ab7
  4:65511d0e2b55

out branch . non-ascii

  $ hg --encoding utf-8 up æ
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --encoding latin1 out -q ../branch#.
  2:df5a44224d4e
  3:4f4a5125ca10
  $ hg --encoding latin1 out -q -b .
  2:df5a44224d4e
  3:4f4a5125ca10

clone branch b

  $ cd ..
  $ hg clone branch2#b branch3
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 1 files (+1 heads)
  updating to branch b
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg -q -R branch3 heads b
  2:65511d0e2b55
  1:b84708d77ab7
  $ hg -q -R branch3 parents
  2:65511d0e2b55
  $ rm -rf branch3

clone rev a branch b

  $ hg clone -r a branch2#b branch3
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 1 files (+1 heads)
  updating to branch a
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg -q -R branch3 heads b
  2:65511d0e2b55
  1:b84708d77ab7
  $ hg -q -R branch3 parents
  0:5b65ba7c951d
  $ rm -rf branch3