Mercurial > hg
comparison mercurial/revlog.py @ 27650:e7222d326ea2
revlog: remove unnecessary cache validation in _chunks
Previously, we likely called _chunkraw() multiple times in order to
ensure it didn't change out from under us. I'm pretty certain this code
had its origins in the days where we attempted to have thread safety of
localrepository and thus revlog instances.
revlog instances are already not thread safe for writing. And, as of
Mercurial 3.6, hgweb uses a separate localrepository instance per
request, so there should only be a single thread reading a revlog at
a time. We more or less decided that attempting to make classes like
revlog thread safe is a lost cause.
So, this patch removes thread safety from _chunks. As a result, we make
one less call into _chunkraw() when the initial read isn't serviced
by the cache. This translates to savings of 4 function calls overall
and possibly prevents the creation of an additional buffer view into the
cache. I doubt this translates into any real world performance wins
because decompression will almost certainly dwarf time spent in
_chunks(). But it does make the code simpler, so it is an improvement.
author | Gregory Szorc <gregory.szorc@gmail.com> |
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date | Sun, 22 Nov 2015 17:57:35 -0800 |
parents | 6446e9b37c8b |
children | a9e010cd66e1 |
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27649:6446e9b37c8b | 27650:e7222d326ea2 |
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1120 buffer = util.buffer | 1120 buffer = util.buffer |
1121 | 1121 |
1122 l = [] | 1122 l = [] |
1123 ladd = l.append | 1123 ladd = l.append |
1124 | 1124 |
1125 # preload the cache | |
1126 try: | 1125 try: |
1127 while True: | 1126 offset, data = self._chunkraw(revs[0], revs[-1], df=df) |
1128 # ensure that the cache doesn't change out from under us | |
1129 _cache = self._chunkcache | |
1130 self._chunkraw(revs[0], revs[-1], df=df)[1] | |
1131 if _cache == self._chunkcache: | |
1132 break | |
1133 offset, data = _cache | |
1134 except OverflowError: | 1127 except OverflowError: |
1135 # issue4215 - we can't cache a run of chunks greater than | 1128 # issue4215 - we can't cache a run of chunks greater than |
1136 # 2G on Windows | 1129 # 2G on Windows |
1137 return [self._chunk(rev, df=df) for rev in revs] | 1130 return [self._chunk(rev, df=df) for rev in revs] |
1138 | 1131 |