From b630be0922dbaaa50eb174a7740f0d3fb88602da Mon Sep 17 00:00:00 2001 From: Cupertino Miranda Date: Fri, 14 Apr 2023 16:12:20 +0100 Subject: [PATCH] Created tunable to force small pages on stack allocation. Created tunable glibc.pthread.stack_hugetlb to control when hugepages can be used for stack allocation. In case THP are enabled and glibc.pthread.stack_hugetlb is set to 0, glibc will madvise the kernel not to use allow hugepages for stack allocations. Reviewed-by: Adhemerval Zanella --- NEWS | 3 +++ manual/tunables.texi | 15 +++++++++++++++ nptl/allocatestack.c | 6 ++++++ nptl/nptl-stack.c | 1 + nptl/nptl-stack.h | 3 +++ nptl/pthread_mutex_conf.c | 8 ++++++++ sysdeps/nptl/dl-tunables.list | 6 ++++++ 7 files changed, 42 insertions(+) diff --git a/NEWS b/NEWS index 83d082afad..40964d2ee0 100644 --- a/NEWS +++ b/NEWS @@ -21,6 +21,9 @@ Major new features: * PRIb* and PRIB* macros from C2X have been added to . +* A new tunable, glibc.pthread.stack_hugetlb, can be used to disable + Transparent Huge Pages (THP) in stack allocation at pthread_create. + Deprecated and removed features, and other changes affecting compatibility: * In the Linux kernel for the hppa/parisc architecture some of the diff --git a/manual/tunables.texi b/manual/tunables.texi index 70dd2264c5..130f94b2bc 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -459,6 +459,21 @@ registration on behalf of the application. Restartable sequences are a Linux-specific extension. @end deftp +@deftp Tunable glibc.pthread.stack_hugetlb +This tunable controls whether to use Huge Pages in the stacks created by +@code{pthread_create}. This tunable only affects the stacks created by +@theglibc{}, it has no effect on stack assigned with +@code{pthread_attr_setstack}. + +The default is @samp{1} where the system default value is used. Setting +its value to @code{0} enables the use of @code{madvise} with +@code{MADV_NOHUGEPAGE} after stack creation with @code{mmap}. + +This is a memory utilization optimization, since internal glibc setup of either +the thread descriptor and the guard page might force the kernel to move the +thread stack originally backup by Huge Pages to default pages. +@end deftp + @node Hardware Capability Tunables @section Hardware Capability Tunables @cindex hardware capability tunables diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c index c7adbccd6f..f9d8cdfd08 100644 --- a/nptl/allocatestack.c +++ b/nptl/allocatestack.c @@ -369,6 +369,12 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp, if (__glibc_unlikely (mem == MAP_FAILED)) return errno; + /* Do madvise in case the tunable glibc.pthread.stack_hugetlb is + set to 0, disabling hugetlb. */ + if (__glibc_unlikely (__nptl_stack_hugetlb == 0) + && __madvise (mem, size, MADV_NOHUGEPAGE) != 0) + return errno; + /* SIZE is guaranteed to be greater than zero. So we can never get a null pointer back from mmap. */ assert (mem != NULL); diff --git a/nptl/nptl-stack.c b/nptl/nptl-stack.c index 5eb7773575..e829711cb5 100644 --- a/nptl/nptl-stack.c +++ b/nptl/nptl-stack.c @@ -21,6 +21,7 @@ #include size_t __nptl_stack_cache_maxsize = 40 * 1024 * 1024; +int32_t __nptl_stack_hugetlb = 1; void __nptl_stack_list_del (list_t *elem) diff --git a/nptl/nptl-stack.h b/nptl/nptl-stack.h index 34f8bbb15e..cf90b27c2b 100644 --- a/nptl/nptl-stack.h +++ b/nptl/nptl-stack.h @@ -27,6 +27,9 @@ /* Maximum size of the cache, in bytes. 40 MiB by default. */ extern size_t __nptl_stack_cache_maxsize attribute_hidden; +/* Should allow stacks to use hugetlb. (1) is default. */ +extern int32_t __nptl_stack_hugetlb; + /* Check whether the stack is still used or not. */ static inline bool __nptl_stack_in_use (struct pthread *pd) diff --git a/nptl/pthread_mutex_conf.c b/nptl/pthread_mutex_conf.c index 9133384d47..6517899718 100644 --- a/nptl/pthread_mutex_conf.c +++ b/nptl/pthread_mutex_conf.c @@ -44,6 +44,12 @@ TUNABLE_CALLBACK (set_stack_cache_size) (tunable_val_t *valp) __nptl_stack_cache_maxsize = valp->numval; } +static void +TUNABLE_CALLBACK (set_stack_hugetlb) (tunable_val_t *valp) +{ + __nptl_stack_hugetlb = (int32_t) valp->numval; +} + void __pthread_tunables_init (void) { @@ -51,4 +57,6 @@ __pthread_tunables_init (void) TUNABLE_CALLBACK (set_mutex_spin_count)); TUNABLE_GET (stack_cache_size, size_t, TUNABLE_CALLBACK (set_stack_cache_size)); + TUNABLE_GET (stack_hugetlb, int32_t, + TUNABLE_CALLBACK (set_stack_hugetlb)); } diff --git a/sysdeps/nptl/dl-tunables.list b/sysdeps/nptl/dl-tunables.list index bd1ddb121d..4cde9500b6 100644 --- a/sysdeps/nptl/dl-tunables.list +++ b/sysdeps/nptl/dl-tunables.list @@ -33,5 +33,11 @@ glibc { maxval: 1 default: 1 } + stack_hugetlb { + type: INT_32 + minval: 0 + maxval: 1 + default: 1 + } } }