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use MADV_DONTNEED for commit/decommit on macOS

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daan 2020-09-06 12:06:56 -07:00
parent 5ae01fe4d9
commit 828613a694
1 changed files with 19 additions and 4 deletions
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23
src/os.c
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@ -716,20 +716,35 @@ static bool mi_os_commitx(void* addr, size_t size, bool commit, bool conservativ
#elif defined(__wasi__) #elif defined(__wasi__)
// WebAssembly guests can't control memory protection // WebAssembly guests can't control memory protection
#elif defined(MAP_FIXED) && !defined(__APPLE__) #elif defined(MAP_FIXED) && !defined(__APPLE__)
// Linux
if (!commit) { if (!commit) {
// use mmap with MAP_FIXED to discard the existing memory (and reduce commit charge) // decommit: use mmap with MAP_FIXED to discard the existing memory (and reduce rss)
const int fd = mi_unix_mmap_fd(); const int fd = mi_unix_mmap_fd();
void* p = mmap(start, csize, PROT_NONE, (MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE), fd, 0); void* p = mmap(start, csize, PROT_NONE, (MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE), fd, 0);
if (p != start) { err = errno; } if (p != start) { err = errno; }
} }
else { else {
// for commit, just change the protection // commit: just change the protection
err = mprotect(start, csize, (PROT_READ | PROT_WRITE)); err = mprotect(start, csize, (PROT_READ | PROT_WRITE));
if (err != 0) { err = errno; } if (err != 0) { err = errno; }
} }
#else #else
err = mprotect(start, csize, (commit ? (PROT_READ | PROT_WRITE) : PROT_NONE)); // MacOS and others.
if (err != 0) { err = errno; } if (!commit) {
#if defined(MADV_DONTNEED)
// decommit: use MADV_DONTNEED as it decrease rss immediately (unlike MADV_FREE)
err = madvise(start, csize, MADV_DONTNEED);
#else
// decommit: just disable access
err = mprotect(start, csize, PROT_NONE);
if (err != 0) { err = errno; }
#endif
}
else {
// commit: ensure we can access the area
err = mprotect(start, csize, (PROT_READ | PROT_WRITE));
if (err != 0) { err = errno; }
}
#endif #endif
if (err != 0) { if (err != 0) {
_mi_warning_message("%s error: start: %p, csize: 0x%x, err: %i\n", commit ? "commit" : "decommit", start, csize, err); _mi_warning_message("%s error: start: %p, csize: 0x%x, err: %i\n", commit ? "commit" : "decommit", start, csize, err);