glibc/benchtests/thread_create-inputs

## args: int:size_t:size_t
## init: thread_create_init
## includes: pthread.h
## include-sources: thread_create-source.c

## name: stack=1024,guard=1
32, 1024, 1
## name: stack=1024,guard=2
32, 1024, 2

## name: stack=2048,guard=1
32, 2048, 1
## name: stack=2048,guard=2
32, 2048, 2
nptl: Invert the mmap/mprotect logic on allocated stacks (BZ#18988) Current allocate_stack logic for create stacks is to first mmap all the required memory with the desirable memory and then mprotect the guard area with PROT_NONE if required. Although it works as expected, it pessimizes the allocation because it requires the kernel to actually increase commit charge (it counts against the available physical/swap memory available for the system). The only issue is to actually check this change since side-effects are really Linux specific and to actually account them it would require a kernel specific tests to parse the system wide information. On the kernel I checked /proc/self/statm does not show any meaningful difference for vmm and/or rss before and after thread creation. I could only see really meaningful information checking on system wide /proc/meminfo between thread creation: MemFree, MemAvailable, and Committed_AS shows large difference without the patch. I think trying to use these kind of information on a testcase is fragile. The BZ#18988 reports shows that the commit pages are easily seen with mlockall (MCL_FUTURE) (with lock all pages that become mapped in the process) however a more straighfoward testcase shows that pthread_create could be faster using this patch: -- static const int inner_count = 256; static const int outer_count = 128; static void thread1(void arg) { return NULL; } static void sleeper(void arg) { pthread_t ts[inner_count]; for (int i = 0; i < inner_count; i++) pthread_create (&ts[i], &a, thread1, NULL); for (int i = 0; i < inner_count; i++) pthread_join (ts[i], NULL); return NULL; } int main(void) { pthread_attr_init(&a); pthread_attr_setguardsize(&a, 1<<20); pthread_attr_setstacksize(&a, 1134592); pthread_t ts[outer_count]; for (int i = 0; i < outer_count; i++) pthread_create(&ts[i], &a, sleeper, NULL); for (int i = 0; i < outer_count; i++) pthread_join(ts[i], NULL); assert(r == 0); } return 0; } -- On x86_64 (4.4.0-45-generic, gcc 5.4.0) running the small benchtests I see: $ time ./test real 0m3.647s user 0m0.080s sys 0m11.836s While with the patch I see: $ time ./test real 0m0.696s user 0m0.040s sys 0m1.152s So I added a pthread_create benchtest (thread_create) which check the thread creation latency. As for the simple benchtests, I saw improvements in thread creation on all architectures I tested the change. Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu, arm-linux-gnueabihf, powerpc64le-linux-gnu, sparc64-linux-gnu, and sparcv9-linux-gnu. [BZ #18988] * benchtests/thread_create-inputs: New file. * benchtests/thread_create-source.c: Likewise. * support/xpthread_attr_setguardsize.c: Likewise. * support/Makefile (libsupport-routines): Add xpthread_attr_setguardsize object. * support/xthread.h: Add xpthread_attr_setguardsize prototype. * benchtests/Makefile (bench-pthread): Add thread_create. * nptl/allocatestack.c (allocate_stack): Call mmap with PROT_NONE and then mprotect the required area. 2017-01-31 20:01:59 +00:00			`## args: int:size_t:size_t`
			`## init: thread_create_init`
			`## includes: pthread.h`
			`## include-sources: thread_create-source.c`

			`## name: stack=1024,guard=1`
			`32, 1024, 1`
			`## name: stack=1024,guard=2`
			`32, 1024, 2`

			`## name: stack=2048,guard=1`
			`32, 2048, 1`
			`## name: stack=2048,guard=2`
			`32, 2048, 2`