Mercurial > hg
view tests/test-issue522.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> |
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date | Sun, 16 Oct 2016 13:35:23 -0700 |
parents | 2fc86d92c4a9 |
children | 009d0283de5f |
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https://bz.mercurial-scm.org/522 In the merge below, the file "foo" has the same contents in both parents, but if we look at the file-level history, we'll notice that the version in p1 is an ancestor of the version in p2. This test makes sure that we'll use the version from p2 in the manifest of the merge revision. $ hg init $ echo foo > foo $ hg ci -qAm 'add foo' $ echo bar >> foo $ hg ci -m 'change foo' $ hg backout -r tip -m 'backout changed foo' reverting foo changeset 2:4d9e78aaceee backs out changeset 1:b515023e500e $ hg up -C 0 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ touch bar $ hg ci -qAm 'add bar' $ hg merge --debug searching for copies back to rev 1 unmatched files in local: bar resolving manifests branchmerge: True, force: False, partial: False ancestor: bbd179dfa0a7, local: 71766447bdbb+, remote: 4d9e78aaceee foo: remote is newer -> g getting foo 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg debugstate | grep foo m 0 -2 unset foo $ hg st -A foo M foo $ hg ci -m 'merge' $ hg manifest --debug | grep foo c6fc755d7e68f49f880599da29f15add41f42f5a 644 foo $ hg debugindex foo rev offset length ..... linkrev nodeid p1 p2 (re) 0 0 5 ..... 0 2ed2a3912a0b 000000000000 000000000000 (re) 1 5 9 ..... 1 6f4310b00b9a 2ed2a3912a0b 000000000000 (re) 2 14 5 ..... 2 c6fc755d7e68 6f4310b00b9a 000000000000 (re)