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refactor os_overcommit detection

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Daan 2021-10-27 17:39:11 -07:00
parent 0335d32766
commit 5fd77aa198
1 changed files with 33 additions and 29 deletions
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62
src/os.c
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@ -40,7 +40,6 @@ terms of the MIT license. A copy of the license can be found in the file
#if defined(__linux__) #if defined(__linux__)
#include <features.h> #include <features.h>
#include <fcntl.h> #include <fcntl.h>
#include <stdlib.h>
#if defined(__GLIBC__) #if defined(__GLIBC__)
#include <linux/mman.h> // linux mmap flags #include <linux/mman.h> // linux mmap flags
#else #else
@ -98,8 +97,9 @@ static size_t os_alloc_granularity = 4096;
// if non-zero, use large page allocation // if non-zero, use large page allocation
static size_t large_os_page_size = 0; static size_t large_os_page_size = 0;
// if non-zero, enable page overcommit // is memory overcommit allowed?
static int os_overcommit = 0; // set dynamically in _mi_os_init (and if true we use MAP_NORESERVE)
static bool os_overcommit = true;
// OS (small) page size // OS (small) page size
size_t _mi_os_page_size() { size_t _mi_os_page_size() {
@ -189,7 +189,9 @@ static bool mi_win_enable_large_os_pages()
return (ok!=0); return (ok!=0);
} }
void _mi_os_init(void) { void _mi_os_init(void)
{
os_overcommit = false;
// get the page size // get the page size
SYSTEM_INFO si; SYSTEM_INFO si;
GetSystemInfo(&si); GetSystemInfo(&si);
@ -224,10 +226,36 @@ void _mi_os_init(void) {
} }
#elif defined(__wasi__) #elif defined(__wasi__)
void _mi_os_init() { void _mi_os_init() {
os_overcommit = false;
os_page_size = 0x10000; // WebAssembly has a fixed page size: 64KiB os_page_size = 0x10000; // WebAssembly has a fixed page size: 64KiB
os_alloc_granularity = 16; os_alloc_granularity = 16;
} }
#else // generic unix
static void os_detect_overcommit(void) {
#if defined(__linux__)
int fd = open("/proc/sys/vm/overcommit_memory", O_RDONLY);
if (fd < 0) return;
char buf[128];
ssize_t nread = read(fd, &buf, sizeof(buf));
close(fd);
// <https://www.kernel.org/doc/Documentation/vm/overcommit-accounting>
// 0: heuristic overcommit, 1: always overcommit, 2: never overcommit (ignore NORESERVE)
if (nread >= 1) {
os_overcommit = (buf[0] == '0' || buf[0] == '1');
}
#elif defined(__FreeBSD__)
int val = 0;
size_t olen = sizeof(val);
if (sysctlbyname("vm.overcommit", &val, &olen, NULL, 0) == 0) {
os_overcommit = (val != 0);
}
#else #else
// default: overcommit is true
#endif
}
void _mi_os_init() { void _mi_os_init() {
// get the page size // get the page size
long result = sysconf(_SC_PAGESIZE); long result = sysconf(_SC_PAGESIZE);
@ -236,31 +264,7 @@ void _mi_os_init() {
os_alloc_granularity = os_page_size; os_alloc_granularity = os_page_size;
} }
large_os_page_size = 2*MiB; // TODO: can we query the OS for this? large_os_page_size = 2*MiB; // TODO: can we query the OS for this?
#if defined(__linux__) os_detect_overcommit();
int fd = open("/proc/sys/vm/overcommit_memory", O_RDONLY);
if (fd != -1) {
char buf[1] = {0};
if (read(fd, buf, sizeof(buf)) == sizeof(buf)) {
switch (buf[0]) {
case '0': // heuristic mode
case '1': // always
os_overcommit = 1;
break;
default: // never regardless
os_overcommit = 0;
}
}
close(fd);
}
#elif defined(__FreeBSD__)
int val = 0;
size_t olen = sizeof(val);
if (sysctlbyname("vm.overcommit", &val, &olen, NULL, 0) == 0) {
os_overcommit = val;
}
#elif defined(__NetBSD__) || defined(__HAIKU__)
os_overcommit = 1;
#endif
} }
#endif #endif