Michał Kępień 7aa7b6474b Prevent memory bloat caused by a jemalloc quirk ... Since version 5.0.0, decay-based purging is the only available dirty page cleanup mechanism in jemalloc. It relies on so-called tickers, which are simple data structures used for ensuring that certain actions are taken "once every N times". Ticker data (state) is stored in a thread-specific data structure called tsd in jemalloc parlance. Ticks are triggered when extents are allocated and deallocated. Once every 1000 ticks, jemalloc attempts to release some of the dirty pages hanging around (if any). This allows memory use to be kept in check over time. This dirty page cleanup mechanism has a quirk. If the first allocator-related action for a given thread is a free(), a minimally-initialized tsd is set up which does not include ticker data. When that thread subsequently calls *alloc(), the tsd transitions to its nominal state, but due to a certain flag being set during minimal tsd initialization, ticker data remains unallocated. This prevents decay-based dirty page purging from working, effectively enabling memory exhaustion over time. [1] The quirk described above has been addressed (by moving ticker state to a different structure) in jemalloc's development branch [2], but not in any numbered jemalloc version released to date (the latest one being 5.2.1 as of this writing). Work around the problem by ensuring that every thread spawned by isc_thread_create() starts with a malloc() call. Avoid immediately calling free() for the dummy allocation to prevent an optimizing compiler from stripping away the malloc() + free() pair altogether. An alternative implementation of this workaround was considered that used a pair of isc_mem_create() + isc_mem_destroy() calls instead of malloc() + free(), enabling the change to be fully contained within isc__trampoline_run() (i.e. to not touch struct isc__trampoline), as the compiler is not allowed to strip away arbitrary function calls. However, that solution was eventually dismissed as it triggered ThreadSanitizer reports when tools like dig, nsupdate, or rndc exited abruptly without waiting for all worker threads to finish their work. [1] https://github.com/jemalloc/jemalloc/issues/2251 [2] c259323ab3		2022-04-21 14:19:39 +02:00
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bind9	More explicit dns64 prefix errors	2022-03-25 10:59:15 +01:00
dns	Tighten DBC restrictions on message sections	2022-04-19 22:12:38 +00:00
irs	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
isc	Prevent memory bloat caused by a jemalloc quirk	2022-04-21 14:19:39 +02:00
isccc	Keep the list of scheduled events on the timer	2022-04-01 23:45:23 +02:00
isccfg	Rename the configuration option to load balance sockets to reuseport	2022-04-06 17:03:57 +02:00
ns	Allow listening on less than nworkers threads	2022-04-19 11:08:13 +02:00
.gitignore	The isc/platform.h header has been completely removed	2021-07-06 05:33:48 +00:00
Makefile.am	move samples/resolve.c to bin/tests/system	2021-04-16 14:29:43 +02:00
unit-test-driver.sh.in	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00