The current thread name reading path updates the name every time, which requires
both alloc and dalloc -- and the temporary NULL value in the middle causes races
where the prof dump read path gets NULLed in the middle.
Minimize the changes in this commit to isolate the bugfix testing; will also
refactor the whole thread name paths later.
The added hooks hooks.prof_sample and hooks.prof_sample_free are intended to
allow advanced users to track additional information, to enable new ways of
profiling on top of the jemalloc heap profile and sample features.
The sample hook is invoked after the allocation and backtracing, and forwards
the both the allocation and backtrace to the user hook; the sample_free hook
happens before the actual deallocation, and forwards only the ptr and usz to the
hook.
Allows the use of getenv() rather than secure_getenv() to read MALLOC_CONF.
This helps in situations where hosts are under full control, and setting
MALLOC_CONF is needed while also setuid. Disabled by default.
Previously if a thread does only allocations, it stays on the slow path /
minimal initialized state forever. However, dealloc-only is a valid pattern for
dedicated reclamation threads -- this means thread cache is disabled (no batched
flush) for them, which causes high overhead and contention.
Added the condition to fully initialize TSD when a fair amount of dealloc
activities are observed.
Add new runtime option `debug_double_free_max_scan` that specifies the max
number of stack entries to scan in the cache bit when trying to detect the
double free bug (currently debug build only).
In arena_stats_merge() first nmalloc was read, and after ndalloc.
However with this order, it is possible for some thread to incement
ndalloc in between, and then nmalloc < ndalloc, and assertion will fail,
like again found by ClickHouse CI [1] (even after #2234).
[1]: https://github.com/ClickHouse/ClickHouse/issues/31531
Swap the order to avoid possible assertion.
Cc: @interwq
Follow-up for: #2234
The option makes jemalloc use prctl with PR_SET_VMA to tag memory mappings with
"jemalloc_pg" or "jemalloc_pg_overcommit". This allows to easily identify
jemalloc's mappings in /proc/<pid>/maps. PR_SET_VMA is only available in Linux
5.17 and above.
Default SEC max_alloc option value was 32k, disabling SEC for platforms with
lg-page=16. This change enables SEC for all platforms, making minimum max_alloc
value equal to PAGE.
Due to a bug in sec initialization, the number of cached size classes
was equal to 198. The bug caused the creation of more than a hundred of
unused bins, although it didn't affect the caching logic.
Before this commit, in case FreeBSD libc jemalloc was overridden by another
jemalloc, proper thread shutdown callback was involved only for the overriding
jemalloc. A call to _malloc_thread_cleanup from libthr would be redirected to
user jemalloc, leaving data about dead threads hanging in system jemalloc. This
change tackles the issue in two ways. First, for current and old system
jemallocs, which we can not modify, the overriding jemalloc would locate and
invoke system cleanup routine. For upcoming jemalloc integrations, the cleanup
registering function will also be redirected to user jemalloc, which means that
system jemalloc's cleanup routine will be registered in user's jemalloc and a
single call to _malloc_thread_cleanup will be sufficient to invoke both
callbacks.
While calculating the number of stashed pointers, multiple variables
potentially modified by a concurrent thread were used for the
calculation. This led to some inconsistencies, correctly detected by
the assertions. The change eliminates some possible inconsistencies by
using unmodified variables and only once a concurrently modified one.
The assertions are omitted for the cases where we acknowledge potential
inconsistencies too.
The option makes the process to exit with error code 1 if a memory leak
is detected. This is useful for implementing automated tools that rely
on leak detection.
With DSS as primary, the default merge impl will (correctly) decline to merge
when one of the extent is non-dss. The error path should tolerate the
not-merged extent being in a merging state.
On deallocation, sampled pointers (specially aligned) get junked and stashed
into tcache (to prevent immediate reuse). The expected behavior is to have
read-after-free corrupted and stopped by the junk-filling, while
write-after-free is checked when flushing the stashed pointers.
Also refactor the handling of the non-deterministic case. Notably allow the
case with narenas set to proceed w/o warnings, to not affect existing valid use
cases.
nstime module guarantees monotonic clock update within a single nstime_t. This
means, if two separate nstime_t variables are read and updated separately,
nstime_subtract between them may result in underflow. Fixed by switching to the
time since utility provided by nstime.
Determinitic number of CPUs is important for percpu arena to work
correctly, since it uses cpu index - sched_getcpu(), and if it will
greater then number of CPUs bad thing will happen, or assertion will be
failed in debug build:
<jemalloc>: ../contrib/jemalloc/src/jemalloc.c:321: Failed assertion: "ind <= narenas_total_get()"
Aborted (core dumped)
Number of CPUs can be obtained from the following places:
- sched_getaffinity()
- sysconf(_SC_NPROCESSORS_ONLN)
- sysconf(_SC_NPROCESSORS_CONF)
For the sched_getaffinity() you may simply use taskset(1) to run program
on a different cpu, and in case it will be not first, percpu will work
incorrectly, i.e.:
$ taskset --cpu-list $(( $(getconf _NPROCESSORS_ONLN)-1 )) <your_program>
_SC_NPROCESSORS_ONLN uses /sys/devices/system/cpu/online, LXD/LXC
virtualize /sys/devices/system/cpu/online file [1], and so when you run
container with limited limits.cpus it will bind randomly selected CPU to
it
[1]: https://github.com/lxc/lxcfs/issues/301
_SC_NPROCESSORS_CONF uses /sys/devices/system/cpu/cpu*, and AFAIK nobody
playing with dentries there.
So if all three of these are equal, percpu arenas should work correctly.
And a small note regardless _SC_NPROCESSORS_ONLN/_SC_NPROCESSORS_CONF,
musl uses sched_getaffinity() for both. So this will also increase the
entropy.
Also note, that you can check is percpu arena really applied using
abort_conf:true.
Refs: https://github.com/jemalloc/jemalloc/pull/1939
Refs: https://github.com/ClickHouse/ClickHouse/issues/32806
v2: move malloc_cpu_count_is_deterministic() into
malloc_init_hard_recursible() since _SC_NPROCESSORS_CONF does
allocations for readdir()
v3:
- mark cpu_count_is_deterministic static
- check only if percpu arena is enabled
- check narenas
