nptl: Add glibc.pthread.stack_cache_size
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Commit Message
The valgrind/helgrind test suite needs a way to make stack dealloction
more prompt, and this feature seems to be generally useful.
Tested on i686-linux-gnu, x86_64-linux-gnu. Built with
build-many-glibcs.py. Confirmed manually with GDB that the stack cache
size indeed changes as a result of setting the tunable.
---
NEWS | 3 +++
manual/tunables.texi | 9 +++++++++
nptl/nptl-stack.c | 7 +++----
nptl/nptl-stack.h | 3 +++
nptl/pthread_mutex_conf.c | 9 +++++++++
sysdeps/nptl/dl-tunables.list | 4 ++++
6 files changed, 31 insertions(+), 4 deletions(-)
Comments
On Jun 28 2021, Florian Weimer via Libc-alpha wrote:
> diff --git a/nptl/nptl-stack.h b/nptl/nptl-stack.h
> index a6bd8df77f..19d040431e 100644
> --- a/nptl/nptl-stack.h
> +++ b/nptl/nptl-stack.h
> @@ -25,6 +25,9 @@
> #include <list.h>
> #include <stdbool.h>
>
> +/* Maximum size in kB of cache. 40MiBi by default. */
> +extern size_t __nptl_stack_cache_maxsize attribute_hidden;
Kilobytes or bytes?
Andreas.
* Andreas Schwab:
> On Jun 28 2021, Florian Weimer via Libc-alpha wrote:
>
>> diff --git a/nptl/nptl-stack.h b/nptl/nptl-stack.h
>> index a6bd8df77f..19d040431e 100644
>> --- a/nptl/nptl-stack.h
>> +++ b/nptl/nptl-stack.h
>> @@ -25,6 +25,9 @@
>> #include <list.h>
>> #include <stdbool.h>
>>
>> +/* Maximum size in kB of cache. 40MiBi by default. */
>> +extern size_t __nptl_stack_cache_maxsize attribute_hidden;
>
> Kilobytes or bytes?
Oh, looks like the original comment was wrong. stackblock_size, among
other things, is measured in bytes. I have changed it locally to:
/* Maximum size of the cache, in bytes. 40 MiB by default. */
Thanks,
Florian
On 6/28/21 5:14 PM, Florian Weimer via Libc-alpha wrote:
> The valgrind/helgrind test suite needs a way to make stack dealloction
> more prompt, and this feature seems to be generally useful.
>
> Tested on i686-linux-gnu, x86_64-linux-gnu. Built with
> build-many-glibcs.py. Confirmed manually with GDB that the stack cache
> size indeed changes as a result of setting the tunable.
>
> ---
> NEWS | 3 +++
> manual/tunables.texi | 9 +++++++++
> nptl/nptl-stack.c | 7 +++----
> nptl/nptl-stack.h | 3 +++
> nptl/pthread_mutex_conf.c | 9 +++++++++
> sysdeps/nptl/dl-tunables.list | 4 ++++
> 6 files changed, 31 insertions(+), 4 deletions(-)
>
> diff --git a/NEWS b/NEWS
> index 37ba4334c6..a107b14112 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -49,6 +49,9 @@ Major new features:
> with names ending with .conf to logically classify the converter modules in
> that directory.
>
> +* A new tunable, glibc.pthread.stack_cache_size, can be used to
> + configure the thread stack size on Linux.
configure the size of the thread stack cache.
> +
> Deprecated and removed features, and other changes affecting compatibility:
>
> * The function pthread_mutex_consistent_np has been deprecated; programs
> diff --git a/manual/tunables.texi b/manual/tunables.texi
> index fe7c1313cc..d5d957fb5b 100644
> --- a/manual/tunables.texi
> +++ b/manual/tunables.texi
> @@ -402,6 +402,15 @@ is acquired.
> The default value of this tunable is @samp{100}.
> @end deftp
>
> +@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
> +
> @node Hardware Capability Tunables
> @section Hardware Capability Tunables
> @cindex hardware capability tunables
> diff --git a/nptl/nptl-stack.c b/nptl/nptl-stack.c
> index 1a0c460ba8..d04feb0683 100644
> --- a/nptl/nptl-stack.c
> +++ b/nptl/nptl-stack.c
> @@ -21,8 +21,7 @@
> #include <ldsodefs.h>
> #include <pthreadP.h>
>
> -/* Maximum size in kB of cache. 40MiBi by default. */
> -static const size_t stack_cache_maxsize = 40 * 1024 * 1024;
> +size_t __nptl_stack_cache_maxsize = 40 * 1024 * 1024;
>
> void
> __nptl_stack_list_del (list_t *elem)
> @@ -103,8 +102,8 @@ queue_stack (struct pthread *stack)
> __nptl_stack_list_add (&stack->list, &GL (dl_stack_cache));
>
> GL (dl_stack_cache_actsize) += stack->stackblock_size;
> - if (__glibc_unlikely (GL (dl_stack_cache_actsize) > stack_cache_maxsize))
> - __nptl_free_stacks (stack_cache_maxsize);
> + if (GL (dl_stack_cache_actsize) > __nptl_stack_cache_maxsize)
> + __nptl_free_stacks (__nptl_stack_cache_maxsize);
Not a strong preference, but maybe this still remains just as unlikely?
A bulk of use cases shouldn't need frequent freeing.
> }
>
> void
> diff --git a/nptl/nptl-stack.h b/nptl/nptl-stack.h
> index a6bd8df77f..19d040431e 100644
> --- a/nptl/nptl-stack.h
> +++ b/nptl/nptl-stack.h
> @@ -25,6 +25,9 @@
> #include <list.h>
> #include <stdbool.h>
>
> +/* Maximum size in kB of cache. 40MiBi by default. */
Comment needs fixing as Andreas pointed out.
> +extern size_t __nptl_stack_cache_maxsize attribute_hidden;
> +
> /* 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 e6235dea47..c8f171c995 100644
> --- a/nptl/pthread_mutex_conf.c
> +++ b/nptl/pthread_mutex_conf.c
> @@ -23,6 +23,7 @@
> #include <stdbool.h>
> #include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
> #include <elf/dl-tunables.h>
> +#include <nptl-stack.h>
>
> struct mutex_config __mutex_aconf =
> {
> @@ -38,10 +39,18 @@ TUNABLE_CALLBACK (set_mutex_spin_count) (tunable_val_t *valp)
> __mutex_aconf.spin_count = (int32_t) (valp)->numval;
> }
>
> +static void
> +TUNABLE_CALLBACK (set_stack_cache_size) (tunable_val_t *valp)
> +{
> + __nptl_stack_cache_maxsize = valp->numval;
> +}
> +
> void
> __pthread_tunables_init (void)
> {
> TUNABLE_GET (mutex_spin_count, int32_t,
> TUNABLE_CALLBACK (set_mutex_spin_count));
> + TUNABLE_GET (stack_cache_size, size_t,
> + TUNABLE_CALLBACK (set_stack_cache_size));
> }
> #endif
OK.
> diff --git a/sysdeps/nptl/dl-tunables.list b/sysdeps/nptl/dl-tunables.list
> index e3f6432e60..ac5d053298 100644
> --- a/sysdeps/nptl/dl-tunables.list
> +++ b/sysdeps/nptl/dl-tunables.list
> @@ -23,5 +23,9 @@ glibc {
> maxval: 32767
> default: 100
> }
> + stack_cache_size {
> + type: SIZE_T
> + default: 41943040
> + }
> }
> }
OK.
* Siddhesh Poyarekar:
>> index 37ba4334c6..a107b14112 100644
>> --- a/NEWS
>> +++ b/NEWS
>> @@ -49,6 +49,9 @@ Major new features:
>> with names ending with .conf to logically classify the converter modules in
>> that directory.
>> +* A new tunable, glibc.pthread.stack_cache_size, can be used to
>> + configure the thread stack size on Linux.
>
> configure the size of the thread stack cache.
Fixed.
>> diff --git a/nptl/nptl-stack.c b/nptl/nptl-stack.c
>> index 1a0c460ba8..d04feb0683 100644
>> --- a/nptl/nptl-stack.c
>> +++ b/nptl/nptl-stack.c
>> @@ -21,8 +21,7 @@
>> #include <ldsodefs.h>
>> #include <pthreadP.h>
>> -/* Maximum size in kB of cache. 40MiBi by default. */
>> -static const size_t stack_cache_maxsize = 40 * 1024 * 1024;
>> +size_t __nptl_stack_cache_maxsize = 40 * 1024 * 1024;
>> void
>> __nptl_stack_list_del (list_t *elem)
>> @@ -103,8 +102,8 @@ queue_stack (struct pthread *stack)
>> __nptl_stack_list_add (&stack->list, &GL (dl_stack_cache));
>> GL (dl_stack_cache_actsize) += stack->stackblock_size;
>> - if (__glibc_unlikely (GL (dl_stack_cache_actsize) > stack_cache_maxsize))
>> - __nptl_free_stacks (stack_cache_maxsize);
>> + if (GL (dl_stack_cache_actsize) > __nptl_stack_cache_maxsize)
>> + __nptl_free_stacks (__nptl_stack_cache_maxsize);
>
> Not a strong preference, but maybe this still remains just as
> unlikely? A bulk of use cases shouldn't need frequent freeing.
I'm going to bring it back in a v2.
Thanks,
Florian
@@ -49,6 +49,9 @@ Major new features:
with names ending with .conf to logically classify the converter modules in
that directory.
+* A new tunable, glibc.pthread.stack_cache_size, can be used to
+ configure the thread stack size on Linux.
+
Deprecated and removed features, and other changes affecting compatibility:
* The function pthread_mutex_consistent_np has been deprecated; programs
@@ -402,6 +402,15 @@ is acquired.
The default value of this tunable is @samp{100}.
@end deftp
+@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
+
@node Hardware Capability Tunables
@section Hardware Capability Tunables
@cindex hardware capability tunables
@@ -21,8 +21,7 @@
#include <ldsodefs.h>
#include <pthreadP.h>
-/* Maximum size in kB of cache. 40MiBi by default. */
-static const size_t stack_cache_maxsize = 40 * 1024 * 1024;
+size_t __nptl_stack_cache_maxsize = 40 * 1024 * 1024;
void
__nptl_stack_list_del (list_t *elem)
@@ -103,8 +102,8 @@ queue_stack (struct pthread *stack)
__nptl_stack_list_add (&stack->list, &GL (dl_stack_cache));
GL (dl_stack_cache_actsize) += stack->stackblock_size;
- if (__glibc_unlikely (GL (dl_stack_cache_actsize) > stack_cache_maxsize))
- __nptl_free_stacks (stack_cache_maxsize);
+ if (GL (dl_stack_cache_actsize) > __nptl_stack_cache_maxsize)
+ __nptl_free_stacks (__nptl_stack_cache_maxsize);
}
void
@@ -25,6 +25,9 @@
#include <list.h>
#include <stdbool.h>
+/* Maximum size in kB of cache. 40MiBi by default. */
+extern size_t __nptl_stack_cache_maxsize attribute_hidden;
+
/* Check whether the stack is still used or not. */
static inline bool
__nptl_stack_in_use (struct pthread *pd)
@@ -23,6 +23,7 @@
#include <stdbool.h>
#include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
#include <elf/dl-tunables.h>
+#include <nptl-stack.h>
struct mutex_config __mutex_aconf =
{
@@ -38,10 +39,18 @@ TUNABLE_CALLBACK (set_mutex_spin_count) (tunable_val_t *valp)
__mutex_aconf.spin_count = (int32_t) (valp)->numval;
}
+static void
+TUNABLE_CALLBACK (set_stack_cache_size) (tunable_val_t *valp)
+{
+ __nptl_stack_cache_maxsize = valp->numval;
+}
+
void
__pthread_tunables_init (void)
{
TUNABLE_GET (mutex_spin_count, int32_t,
TUNABLE_CALLBACK (set_mutex_spin_count));
+ TUNABLE_GET (stack_cache_size, size_t,
+ TUNABLE_CALLBACK (set_stack_cache_size));
}
#endif
@@ -23,5 +23,9 @@ glibc {
maxval: 32767
default: 100
}
+ stack_cache_size {
+ type: SIZE_T
+ default: 41943040
+ }
}
}