Mercurial > hg
view mercurial/revlogutils/sidedata.py @ 45515:89f0d9f87701
branchmap: add a cache validation cache, avoid expensive re-hash on every use
In a pathological `hg log` case, we end up executing the branchmap validity
checking twice per commit displayed. Or maybe we always do, and I just noticed
because it's really slow in this repo for some reason.
Before:
```
Time (mean ± σ): 9.816 s ± 0.071 s [User: 9.435 s, System: 0.392 s]
Range (min … max): 9.709 s … 9.920 s
```
After:
```
Time (mean ± σ): 8.671 s ± 0.078 s [User: 8.309 s, System: 0.392 s]
Range (min … max): 8.594 s … 8.816 s
```
Differential Revision: https://phab.mercurial-scm.org/D9023
author | Kyle Lippincott <spectral@google.com> |
---|---|
date | Wed, 16 Sep 2020 12:13:46 -0700 |
parents | a61287a95dc3 |
children | 9a6b409b8ebc |
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# sidedata.py - Logic around store extra data alongside revlog revisions # # Copyright 2019 Pierre-Yves David <pierre-yves.david@octobus.net) # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. """core code for "sidedata" support The "sidedata" are stored alongside the revision without actually being part of its content and not affecting its hash. It's main use cases is to cache important information related to a changesets. The current implementation is experimental and subject to changes. Do not rely on it in production. Sidedata are stored in the revlog itself, withing the revision rawtext. They are inserted, removed from it using the flagprocessors mechanism. The following format is currently used:: initial header: <number of sidedata; 2 bytes> sidedata (repeated N times): <sidedata-key; 2 bytes> <sidedata-entry-length: 4 bytes> <sidedata-content-sha1-digest: 20 bytes> <sidedata-content; X bytes> normal raw text: <all bytes remaining in the rawtext> This is a simple and effective format. It should be enought to experiment with the concept. """ from __future__ import absolute_import import struct from .. import error from ..utils import hashutil ## sidedata type constant # reserve a block for testing purposes. SD_TEST1 = 1 SD_TEST2 = 2 SD_TEST3 = 3 SD_TEST4 = 4 SD_TEST5 = 5 SD_TEST6 = 6 SD_TEST7 = 7 # key to store copies related information SD_P1COPIES = 8 SD_P2COPIES = 9 SD_FILESADDED = 10 SD_FILESREMOVED = 11 # internal format constant SIDEDATA_HEADER = struct.Struct('>H') SIDEDATA_ENTRY = struct.Struct('>HL20s') def sidedatawriteprocessor(rl, text, sidedata): sidedata = list(sidedata.items()) sidedata.sort() rawtext = [SIDEDATA_HEADER.pack(len(sidedata))] for key, value in sidedata: digest = hashutil.sha1(value).digest() rawtext.append(SIDEDATA_ENTRY.pack(key, len(value), digest)) for key, value in sidedata: rawtext.append(value) rawtext.append(bytes(text)) return b''.join(rawtext), False def sidedatareadprocessor(rl, text): sidedata = {} offset = 0 (nbentry,) = SIDEDATA_HEADER.unpack(text[: SIDEDATA_HEADER.size]) offset += SIDEDATA_HEADER.size dataoffset = SIDEDATA_HEADER.size + (SIDEDATA_ENTRY.size * nbentry) for i in range(nbentry): nextoffset = offset + SIDEDATA_ENTRY.size key, size, storeddigest = SIDEDATA_ENTRY.unpack(text[offset:nextoffset]) offset = nextoffset # read the data associated with that entry nextdataoffset = dataoffset + size entrytext = text[dataoffset:nextdataoffset] readdigest = hashutil.sha1(entrytext).digest() if storeddigest != readdigest: raise error.SidedataHashError(key, storeddigest, readdigest) sidedata[key] = entrytext dataoffset = nextdataoffset text = text[dataoffset:] return text, True, sidedata def sidedatarawprocessor(rl, text): # side data modifies rawtext and prevent rawtext hash validation return False processors = ( sidedatareadprocessor, sidedatawriteprocessor, sidedatarawprocessor, )