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Recently one tricky assertion of jemalloc had been discovered [1]:
Failed assertion: "nstime_compare(&decay->epoch, new_time) <= 0"
[1]: https://github.com/ClickHouse/ClickHouse/issues/66193
And as it turns out it is really possible for CLOCK_MONOTONIC_COARSE to
go backwards, in a nutshell it can be done with ADJ_FREQUENCY, you can
find example here [2]. And I can't trigger this issue for non-coarse
clocks.
[2]: https://gist.github.com/azat/7ea7f50ed75591b1af2d675a240ea94c?permalink_comment_id=5119222#gistcomment-5119222
But, jemalloc do not call clock_gettime() that frequently (I've verified
it), so it can use non-coarse version - CLOCK_MONOTONIC
I've also measured the latency of CLOCK_MONOTONIC and
CLOCK_MONOTONIC_COARSE, and it is 20ns vs 4ns per call [3], so make this
change affect performance you need really frequently calls of
clock_gettime.
[3]: https://gist.github.com/azat/622fa1f9a5d8e7d546ee9d294501961d?permalink_comment_id=5119245#gistcomment-5119245
Interesting, that this bug started to appears only after jemalloc heap
profiler had been enabled by default [4], no clue why (I would believe
more in a more frequent calls to clock_adjtime(ADJ_FREQUENCY), but I
can't verify this)
[4]: https://github.com/ClickHouse/ClickHouse/pull/65702
To be continued...
Fixes: https://github.com/ClickHouse/ClickHouse/issues/66193
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
18 lines
895 B
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18 lines
895 B
Plaintext
It allows to integrate JEMalloc into CMake project.
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- Remove JEMALLOC_HAVE_ATTR_FORMAT_GNU_PRINTF because it's non standard.
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- Added JEMALLOC_CONFIG_MALLOC_CONF substitution
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- Add musl support (USE_MUSL)
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- Also note, that darwin build requires JEMALLOC_PREFIX, while others do not
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- JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE should be disabled
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CLOCK_MONOTONIC_COARSE can go backwards after clock_adjtime(ADJ_FREQUENCY)
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Let's disable it for now, and this menas that CLOCK_MONOTONIC will be used,
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and this, should not be a problem, since:
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- jemalloc do not call clock_gettime() that frequently
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- the difference is CLOCK_MONOTONIC 20ns and CLOCK_MONOTONIC_COARSE 4ns
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This can be done with the following command:
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gg JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE | cut -d: -f1 | xargs sed -i 's@#define JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE@/* #undef JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE */@'
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