perf: clear vfs audit_cache before each run When generating a stream clone, we spend a large amount of time auditing path. Before this changes, the first run was warming the vfs cache for the other runs, leading to a large runtime difference and a "faulty" reported timing for the operation. We now clear this important cache between run to get a more realistic timing. Below are some example of median time change when clearing these cases. The maximum time for a run did not changed significantly. ### data-env-vars.name = mozilla-central-2018-08-01-zstd-sparse-revlog # benchmark.name = hg.perf.exchange.stream.generate # bin-env-vars.hg.flavor = default # bin-env-vars.hg.py-re2-module = default # benchmark.variants.version = latest no-clearing: 17.289905 cache-clearing: 21.587965 (+24.86%, +4.30) ## data-env-vars.name = mozilla-central-2024-03-22-zstd-sparse-revlog no-clearing: 32.670748 cache-clearing: 40.467095 (+23.86%, +7.80) ## data-env-vars.name = mozilla-try-2019-02-18-zstd-sparse-revlog no-clearing: 37.838858 cache-clearing: 46.072749 (+21.76%, +8.23) ## data-env-vars.name = mozilla-unified-2024-03-22-zstd-sparse-revlog no-clearing: 32.969395 cache-clearing: 39.646209 (+20.25%, +6.68) In addition, this significantly reduce the timing difference between the performance command, from the perf extensions and a `real `hg bundle` call producing a stream bundle. Some significant differences remain especially on the "mozilla-try" repositories, but they are now smaller. Note that some of that difference will actually not be attributable to the stream generation (like maybe phases or branch map computation). Below are some benchmarks done on a currently draft changeset fixing some unrelated slowness in `hg bundle` (34a78972af409d1ff37c29e60f6ca811ad1a457d) ### data-env-vars.name = mozilla-central-2018-08-01-zstd-sparse-revlog # bin-env-vars.hg.flavor = default # bin-env-vars.hg.py-re2-module = default hg.perf.exchange.stream.generate: 21.587965 hg.command.bundle: 24.301799 (+12.57%, +2.71) ## data-env-vars.name = mozilla-central-2024-03-22-zstd-sparse-revlog hg.perf.exchange.stream.generate: 40.467095 hg.command.bundle: 44.831317 (+10.78%, +4.36) ## data-env-vars.name = mozilla-unified-2024-03-22-zstd-sparse-revlog hg.perf.exchange.stream.generate: 39.646209 hg.command.bundle: 45.395258 (+14.50%, +5.75) ## data-env-vars.name = mozilla-try-2019-02-18-zstd-sparse-revlog hg.perf.exchange.stream.generate: 46.072749 hg.command.bundle: 55.882608 (+21.29%, +9.81) ## data-env-vars.name = mozilla-try-2023-03-22-zlib-general-delta hg.perf.exchange.stream.generate: 334.716708 hg.command.bundle: 377.856767 (+12.89%, +43.14) ## data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog hg.perf.exchange.stream.generate: 302.972301 hg.command.bundle: 326.098755 (+7.63%, +23.13)

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import io

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import unittest

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from mercurial import util

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class CappedReaderTests(unittest.TestCase):

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    def testreadfull(self):

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        source = io.BytesIO(b'x' * 100)

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        reader = util.cappedreader(source, 10)

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        res = reader.read(10)

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        self.assertEqual(res, b'x' * 10)

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        self.assertEqual(source.tell(), 10)

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        source.seek(0)

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        reader = util.cappedreader(source, 15)

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        res = reader.read(16)

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        self.assertEqual(res, b'x' * 15)

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        self.assertEqual(source.tell(), 15)

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        source.seek(0)

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        reader = util.cappedreader(source, 100)

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        res = reader.read(100)

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        self.assertEqual(res, b'x' * 100)

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        self.assertEqual(source.tell(), 100)

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        source.seek(0)

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        reader = util.cappedreader(source, 50)

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        res = reader.read()

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        self.assertEqual(res, b'x' * 50)

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        self.assertEqual(source.tell(), 50)

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        source.seek(0)

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    def testreadnegative(self):

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        source = io.BytesIO(b'x' * 100)

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        reader = util.cappedreader(source, 20)

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        res = reader.read(-1)

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        self.assertEqual(res, b'x' * 20)

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        self.assertEqual(source.tell(), 20)

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        source.seek(0)

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        reader = util.cappedreader(source, 100)

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        res = reader.read(-1)

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        self.assertEqual(res, b'x' * 100)

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        self.assertEqual(source.tell(), 100)

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        source.seek(0)

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    def testreadmultiple(self):

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        source = io.BytesIO(b'x' * 100)

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        reader = util.cappedreader(source, 10)

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        for i in range(10):

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            res = reader.read(1)

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            self.assertEqual(res, b'x')

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            self.assertEqual(source.tell(), i + 1)

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        self.assertEqual(source.tell(), 10)

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        res = reader.read(1)

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        self.assertEqual(res, b'')

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        self.assertEqual(source.tell(), 10)

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        source.seek(0)

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        reader = util.cappedreader(source, 45)

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        for i in range(4):

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            res = reader.read(10)

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            self.assertEqual(res, b'x' * 10)

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            self.assertEqual(source.tell(), (i + 1) * 10)

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        res = reader.read(10)

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        self.assertEqual(res, b'x' * 5)

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        self.assertEqual(source.tell(), 45)

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    def readlimitpasteof(self):

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        source = io.BytesIO(b'x' * 100)

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        reader = util.cappedreader(source, 1024)

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        res = reader.read(1000)

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        self.assertEqual(res, b'x' * 100)

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        self.assertEqual(source.tell(), 100)

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        res = reader.read(1000)

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        self.assertEqual(res, b'')

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        self.assertEqual(source.tell(), 100)

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if __name__ == '__main__':

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    import silenttestrunner

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    silenttestrunner.main(__name__)