https://bugs.kde.org/show_bug.cgi?id=444488
Bug ID: 444488
Summary: Use glibc.pthread.stack_cache_size tunable
Product: valgrind
Version: unspecified
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: jsew...@acm.org
Reporter: m...@klomp.org
Target Milestone: ---
Since glibc 2.34 the internal/private stack_cache_maxsize variable isn't
available anymore, which causes "sched WARNING: pthread stack cache cannot be
disabled!" when the simhint no_nptl_pthread_stackcache is set (e.g. in
helgrind/tests/tls_threads.vgtest)
See coregrind/pub_core_clientstate.h:
/* glibc nptl pthread systems only, when no-nptl-pthread-stackcache
was given in --sim-hints.
Used for a (kludgy) way to disable the cache of stacks as implemented in
nptl glibc.
Based on internal knowledge of the pthread glibc nptl/allocatestack.c code:
a huge value in stack_cache_actsize (bigger than the constant
stack_cache_maxsize) makes glibc believes the cache is full
and so stacks are always released when a pthread terminates.
Several ugliness in this kludge:
* hardcodes private glibc var name "stack_cache_maxsize"
* based on knowledge of the code of the functions
queue_stack and __free_stacks
* static symbol for "stack_cache_maxsize" must be in
the debug info.
It would be much cleaner to have a documented and supported
way to disable the pthread stack cache. */
extern SizeT* VG_(client__stack_cache_actsize__addr);
Instead we should use the new (in glibc 2.34) tunable:
@deftp Tunable glibc.pthread.stack_cache_size
This tunable configures the maximum size of the stack cache. Once the
stack cache exceeds this size, unused thread stacks are returned to
the kernel, to bring the cache size below this limit.
The value is measured in bytes. The default is @samp{41943040}
(fourty mibibytes).
@end deftp
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