view tests/test-mq-pull-from-bundle.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.

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > mq=
  > [alias]
  > tlog = log --template "{rev}: {desc}\\n"
  > theads = heads --template "{rev}: {desc}\\n"
  > tincoming = incoming --template "{rev}: {desc}\\n"
  > EOF

Setup main:

  $ hg init base
  $ cd base
  $ echo "One" > one
  $ hg add
  adding one
  $ hg ci -m "main: one added"
  $ echo "++" >> one
  $ hg ci -m "main: one updated"

Bundle main:

  $ hg bundle --base=null ../main.hg
  2 changesets found

  $ cd ..

Incoming to fresh repo:

  $ hg init fresh

  $ hg -R fresh tincoming main.hg
  comparing with main.hg
  0: main: one added
  1: main: one updated
  $ test -f ./fresh/.hg/hg-bundle* && echo 'temp. bundle file remained' || true

  $ hg -R fresh tincoming bundle:fresh+main.hg
  comparing with bundle:fresh+main.hg
  0: main: one added
  1: main: one updated


Setup queue:

  $ cd base
  $ hg qinit -c
  $ hg qnew -m "patch: two added" two.patch
  $ echo two > two
  $ hg add
  adding two
  $ hg qrefresh
  $ hg qcommit -m "queue: two.patch added"
  $ hg qpop -a
  popping two.patch
  patch queue now empty

Bundle queue:

  $ hg -R .hg/patches bundle --base=null ../queue.hgq
  1 changesets found
  $ test -f ./fresh/.hg/hg-bundle* && echo 'temp. bundle file remained' || true

  $ cd ..


Clone base:

  $ hg clone base copy
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd copy
  $ hg qinit -c

Incoming queue bundle:

  $ hg -R .hg/patches tincoming ../queue.hgq
  comparing with ../queue.hgq
  0: queue: two.patch added
  $ test -f .hg/hg-bundle* && echo 'temp. bundle file remained' || true

Pull queue bundle:

  $ hg -R .hg/patches pull --update ../queue.hgq
  pulling from ../queue.hgq
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 3 changes to 3 files
  merging series
  2 files updated, 1 files merged, 0 files removed, 0 files unresolved
  $ test -f .hg/patches/hg-bundle* && echo 'temp. bundle file remained' || true

  $ hg -R .hg/patches theads
  0: queue: two.patch added

  $ hg -R .hg/patches tlog
  0: queue: two.patch added

  $ hg qseries
  two.patch

  $ cd ..


Clone base again:

  $ hg clone base copy2
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd copy2
  $ hg qinit -c

Unbundle queue bundle:

  $ hg -R .hg/patches unbundle --update ../queue.hgq
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 3 changes to 3 files
  merging series
  2 files updated, 1 files merged, 0 files removed, 0 files unresolved

  $ hg -R .hg/patches theads
  0: queue: two.patch added

  $ hg -R .hg/patches tlog
  0: queue: two.patch added

  $ hg qseries
  two.patch

  $ cd ..