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linux, checking THP current system settings.

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This commit is contained in:
David Carlier 2021-12-12 14:51:47 +00:00
parent 36edfbc70a
commit 83228bb973
1 changed files with 33 additions and 3 deletions
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36
src/os.c
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@ -97,6 +97,11 @@ 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 defined(MADV_HUGEPAGE)
// only linux supports the THP's notion.
static bool os_transparent_huge_pages = false;
#endif
// is memory overcommit allowed? // is memory overcommit allowed?
// set dynamically in _mi_os_init (and if true we use MAP_NORESERVE) // set dynamically in _mi_os_init (and if true we use MAP_NORESERVE)
static bool os_overcommit = true; static bool os_overcommit = true;
@ -237,13 +242,37 @@ void _mi_os_init() {
#else // generic unix #else // generic unix
static void os_detect_transparent_huge_pages(void) {
#if defined(MADV_HUGEPAGE)
int fd = -1;
size_t i;
static const char *paths[] = {
"/sys/kernel/mm/transparent_hugepage/enabled",
"/sys/kernel/mm/redhat_transparent_hugepage/enabled",
};
for (i = 0; i < sizeof(paths) / sizeof(paths[0]); i ++) {
fd = open(paths[i], O_RDONLY);
if (fd != -1) break;
}
if (fd < 0) return;
char buf[128];
ssize_t nread = read(fd, &buf, sizeof(buf));
close(fd);
if (nread >= 1) {
if (strstr(buf, "[madvise]")) os_transparent_huge_pages = true;
}
#endif
}
static void os_detect_overcommit(void) { static void os_detect_overcommit(void) {
#if defined(__linux__) #if defined(__linux__)
int fd = open("/proc/sys/vm/overcommit_memory", O_RDONLY); int fd = open("/proc/sys/vm/overcommit_memory", O_RDONLY);
if (fd < 0) return; if (fd < 0) return;
char buf[128]; char buf[128];
ssize_t nread = read(fd, &buf, sizeof(buf)); ssize_t nread = read(fd, &buf, sizeof(buf));
close(fd); close(fd);
// <https://www.kernel.org/doc/Documentation/vm/overcommit-accounting> // <https://www.kernel.org/doc/Documentation/vm/overcommit-accounting>
// 0: heuristic overcommit, 1: always overcommit, 2: never overcommit (ignore NORESERVE) // 0: heuristic overcommit, 1: always overcommit, 2: never overcommit (ignore NORESERVE)
if (nread >= 1) { if (nread >= 1) {
@ -269,6 +298,7 @@ void _mi_os_init() {
} }
large_os_page_size = 2*MI_MiB; // TODO: can we query the OS for this? large_os_page_size = 2*MI_MiB; // TODO: can we query the OS for this?
os_detect_overcommit(); os_detect_overcommit();
os_detect_transparent_huge_pages();
} }
#endif #endif
@ -542,7 +572,7 @@ static void* mi_unix_mmap(void* addr, size_t size, size_t try_alignment, int pro
// in that case -- in particular for our large regions (in `memory.c`). // in that case -- in particular for our large regions (in `memory.c`).
// However, some systems only allow THP if called with explicit `madvise`, so // However, some systems only allow THP if called with explicit `madvise`, so
// when large OS pages are enabled for mimalloc, we call `madvise` anyways. // when large OS pages are enabled for mimalloc, we call `madvise` anyways.
if (allow_large && use_large_os_page(size, try_alignment)) { if (os_transparent_huge_pages && allow_large && use_large_os_page(size, try_alignment)) {
if (madvise(p, size, MADV_HUGEPAGE) == 0) { if (madvise(p, size, MADV_HUGEPAGE) == 0) {
*is_large = true; // possibly *is_large = true; // possibly
}; };