Mercurial > hg
annotate mercurial/node.py @ 26379:39d643252b9f
revlog: use existing file handle when reading during _addrevision
_addrevision() may need to read from revlogs as part of computing
deltas. Previously, we would flush existing file handles and open
a new, short-lived file handle to perform the reading.
If we have an existing file handle, it seems logical to reuse it
for reading instead of opening a new file handle. This patch
makes that the new behavior.
After this patch, revlog files are only reopened when adding
revisions if the revlog is switched from inline to non-inline.
On Linux when unbundling a bundle of the mozilla-central repo, this
patch has the following impact on system call counts:
Call Before After Delta
write 827,639 673,390 -154,249
open 700,103 684,089 -16,014
read 74,489 74,489 0
fstat 493,924 461,896 -32,028
close 249,131 233,117 -16,014
stat 242,001 242,001 0
lstat 18,676 18,676 0
lseek 20,268 20,268 0
ioctl 14,652 13,173 -1,479
TOTAL 3,180,758 2,930,679 -250,079
It's worth noting that many of the open() calls fail due to missing
files. That's why there are many more open() calls than close().
Despite the significant system call reduction, this change does not
seem to have a significant performance impact on Linux.
On Windows 10 (not a VM, on a SSD), this patch appears to reduce
unbundle time for mozilla-central from ~960s to ~920s. This isn't
as significant as I was hoping. But a decrease it is nonetheless.
Still, Windows unbundle performance is still >2x slower than Linux.
Despite the lack of significant gains, fewer system calls is fewer
system calls. If nothing else, this will narrow the focus of potential
areas to optimize in the future.
author | Gregory Szorc <gregory.szorc@gmail.com> |
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date | Sun, 27 Sep 2015 16:08:18 -0700 |
parents | 738314da6c75 |
children | 18f50b8cbf1e |
rev | line source |
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1 # node.py - basic nodeid manipulation for mercurial |
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2 # |
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3 # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> |
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4 # |
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5 # This software may be used and distributed according to the terms of the |
10263 | 6 # GNU General Public License version 2 or any later version. |
1089 | 7 |
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node: use absolute_import
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8 from __future__ import absolute_import |
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node: use absolute_import
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9 |
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10 import binascii |
1089 | 11 |
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Define and use nullrev (revision of nullid) instead of -1.
Thomas Arendsen Hein <thomas@intevation.de>
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12 nullrev = -1 |
1089 | 13 nullid = "\0" * 20 |
14 | |
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node: define experimental identifiers for working directory
Yuya Nishihara <yuya@tcha.org>
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15 # pseudo identifiers for working directory |
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16 # (they are experimental, so don't add too many dependencies on them) |
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17 wdirrev = 0x7fffffff |
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18 wdirid = "\xff" * 20 |
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19 |
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manifest: speed up creation of the manifestdict
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20 # This ugly style has a noticeable effect in manifest parsing |
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21 hex = binascii.hexlify |
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22 bin = binascii.unhexlify |
1089 | 23 |
24 def short(node): | |
25 return hex(node[:6]) |