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Fix jemalloc assertion due to non-monotonic CLOCK_MONOTONIC_COARSE

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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>
This commit is contained in:
Azat Khuzhin 2024-07-12 14:40:40 +02:00
parent 860db03d13
commit 22611781b0
8 changed files with 18 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
contrib/jemalloc-cmake/README
View File

@ -4,3 +4,14 @@ It allows to integrate JEMalloc into CMake project.
- Added JEMALLOC_CONFIG_MALLOC_CONF substitution
- Add musl support (USE_MUSL)
- Also note, that darwin build requires JEMALLOC_PREFIX, while others do not
- JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE should be disabled
CLOCK_MONOTONIC_COARSE can go backwards after clock_adjtime(ADJ_FREQUENCY)
Let's disable it for now, and this menas that CLOCK_MONOTONIC will be used,
and this, should not be a problem, since:
- jemalloc do not call clock_gettime() that frequently
- the difference is CLOCK_MONOTONIC 20ns and CLOCK_MONOTONIC_COARSE 4ns
This can be done with the following command:
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 */@'

2
contrib/jemalloc-cmake/include_freebsd_ppc64le/jemalloc/internal/jemalloc_internal_defs.h.in
View File

@ -96,7 +96,7 @@
/*
* Defined if clock_gettime(CLOCK_MONOTONIC_COARSE, ...) is available.
*/
#define JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE
/* #undef JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE */
/*
* Defined if clock_gettime(CLOCK_MONOTONIC, ...) is available.

2
contrib/jemalloc-cmake/include_linux_aarch64/jemalloc/internal/jemalloc_internal_defs.h.in
View File

@ -98,7 +98,7 @@
/*
* Defined if clock_gettime(CLOCK_MONOTONIC_COARSE, ...) is available.
*/
#define JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE
/* #undef JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE */
/*
* Defined if clock_gettime(CLOCK_MONOTONIC, ...) is available.

2
contrib/jemalloc-cmake/include_linux_ppc64le/jemalloc/internal/jemalloc_internal_defs.h.in
View File

@ -98,7 +98,7 @@
/*
* Defined if clock_gettime(CLOCK_MONOTONIC_COARSE, ...) is available.
*/
#define JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE
/* #undef JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE */
/*
* Defined if clock_gettime(CLOCK_MONOTONIC, ...) is available.

2
contrib/jemalloc-cmake/include_linux_riscv64/jemalloc/internal/jemalloc_internal_defs.h.in
View File

@ -98,7 +98,7 @@
/*
* Defined if clock_gettime(CLOCK_MONOTONIC_COARSE, ...) is available.
*/
#define JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE
/* #undef JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE */
/*
* Defined if clock_gettime(CLOCK_MONOTONIC, ...) is available.

2
contrib/jemalloc-cmake/include_linux_s390x/jemalloc/internal/jemalloc_internal_defs.h.in
View File

@ -96,7 +96,7 @@
/*
* Defined if clock_gettime(CLOCK_MONOTONIC_COARSE, ...) is available.
*/
#define JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE
/* #undef JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE */
/*
* Defined if clock_gettime(CLOCK_MONOTONIC, ...) is available.

2
contrib/jemalloc-cmake/include_linux_x86_64/jemalloc/internal/jemalloc_internal_defs.h.in
View File

@ -98,7 +98,7 @@
/*
* Defined if clock_gettime(CLOCK_MONOTONIC_COARSE, ...) is available.
*/
#define JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE
/* #undef JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE */
/*
* Defined if clock_gettime(CLOCK_MONOTONIC, ...) is available.

2
contrib/jemalloc-cmake/include_linux_x86_64_musl/jemalloc/internal/jemalloc_internal_defs.h.in
View File

@ -99,7 +99,7 @@
/*
* Defined if clock_gettime(CLOCK_MONOTONIC_COARSE, ...) is available.
*/
#define JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE
/* #undef JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE */
/*
* Defined if clock_gettime(CLOCK_MONOTONIC, ...) is available.