Mercurial > hg
view tests/test-empty-file.t @ 27475:a2e2a8fa5fd1
revlog: avoid string slice when decompressing u* chunks
Revlog chunks can be stored uncompressed. If the first byte of the
raw data is \0, we store the data as is. Else we prefix it with 'u'.
Before, we performed a string slice to strip out the 'u' prefix.
With this patch, we use a buffer to avoid an extra memory copy and
associated garbage collection overhead.
I was unable to verify any performance impact of this patch. For both
mozilla-central and the hg repos, the number of manifest revisions
with 'u' prefixes is very small - under 1%. So this change likely
isn't called enough to have an impact on manifest reading. However,
the reasoning behind this change is solid, so it should be safe.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Sun, 20 Dec 2015 16:00:27 -0800 |
parents | f2719b387380 |
children |
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$ hg init a $ cd a $ touch empty1 $ hg add empty1 $ hg commit -m 'add empty1' $ touch empty2 $ hg add empty2 $ hg commit -m 'add empty2' $ hg up -C 0 0 files updated, 0 files merged, 1 files removed, 0 files unresolved $ touch empty3 $ hg add empty3 $ hg commit -m 'add empty3' created new head $ hg heads changeset: 2:a1cb177e0d44 tag: tip parent: 0:1e1d9c4e5b64 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: add empty3 changeset: 1:097d2b0e17f6 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: add empty2 $ hg merge 1 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) Before changeset 05257fd28591, we didn't notice the empty file that came from rev 1: $ hg status M empty2 $ hg commit -m merge $ hg manifest --debug tip b80de5d138758541c5f05265ad144ab9fa86d1db 644 empty1 b80de5d138758541c5f05265ad144ab9fa86d1db 644 empty2 b80de5d138758541c5f05265ad144ab9fa86d1db 644 empty3 $ cd ..