Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

linux, checking THP current system settings. #494

Open
wants to merge 1 commit into
base: dev
Choose a base branch
from
Open

linux, checking THP current system settings. #494

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
36 changes: 33 additions & 3 deletions src/os.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -97,6 +97,11 @@ static size_t os_alloc_granularity = 4096;
// if non-zero, use large page allocation
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?
// set dynamically in _mi_os_init (and if true we use MAP_NORESERVE)
static bool os_overcommit = true;
Expand Down Expand Up @@ -237,13 +242,37 @@ void _mi_os_init() {

#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) {
#if defined(__linux__)
int fd = open("/proc/sys/vm/overcommit_memory", O_RDONLY);
if (fd < 0) return;
if (fd < 0) return;
char buf[128];
ssize_t nread = read(fd, &buf, sizeof(buf));
close(fd);
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) {
Expand All @@ -269,6 +298,7 @@ void _mi_os_init() {
}
large_os_page_size = 2*MI_MiB; // TODO: can we query the OS for this?
os_detect_overcommit();
os_detect_transparent_huge_pages();
}
#endif

Expand Down Expand Up @@ -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`).
// However, some systems only allow THP if called with explicit `madvise`, so
// 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) {
*is_large = true; // possibly
};
Expand Down