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add initial support for _mi_prim_reuse and MADV_FREE_REUSABLE on macOS (issue #1097)

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This commit is contained in:
Daan 2025-06-06 17:59:46 -07:00
parent 2d34956bed
commit d389819cc9
8 changed files with 64 additions and 7 deletions
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5
src/prim/emscripten/prim.c
View file

@ -114,6 +114,11 @@ int _mi_prim_reset(void* addr, size_t size) {
return 0;
}
int _mi_prim_reuse(void* addr, size_t size) {
MI_UNUSED(addr); MI_UNUSED(size);
return 0;
}
int _mi_prim_protect(void* addr, size_t size, bool protect) {
MI_UNUSED(addr); MI_UNUSED(size); MI_UNUSED(protect);
return 0;

33
src/prim/unix/prim.c
View file

@ -433,13 +433,27 @@ int _mi_prim_commit(void* start, size_t size, bool* is_zero) {
return err;
}
int _mi_prim_reuse(void* start, size_t size) {
#if defined(__APPLE__) && defined(MADV_FREE_REUSE)
return unix_madvise(start, size, MADV_FREE_REUSE);
#endif
return 0;
}
int _mi_prim_decommit(void* start, size_t size, bool* needs_recommit) {
int err = 0;
// decommit: use MADV_DONTNEED as it decreases rss immediately (unlike MADV_FREE)
err = unix_madvise(start, size, MADV_DONTNEED);
#if !MI_DEBUG && MI_SECURE<=2
*needs_recommit = false;
#if defined(__APPLE__) && defined(MADV_FREE_REUSABLE)
// decommit on macOS: use MADV_FREE_REUSABLE as it does immediate rss accounting (issue #1097)
err = unix_madvise(start, size, MADV_FREE_REUSABLE);
#else
// decommit: use MADV_DONTNEED as it decreases rss immediately (unlike MADV_FREE)
err = unix_madvise(start, size, MADV_DONTNEED);
#endif
#else
// note: don't use MADV_FREE_REUSABLE as the range may contain protected areas
err = unix_madvise(start, size, MADV_DONTNEED);
*needs_recommit = true;
mprotect(start, size, PROT_NONE);
#endif
@ -454,14 +468,21 @@ int _mi_prim_decommit(void* start, size_t size, bool* needs_recommit) {
}
int _mi_prim_reset(void* start, size_t size) {
// We try to use `MADV_FREE` as that is the fastest. A drawback though is that it
int err = 0;
#if defined(__APPLE__) && defined(MADV_FREE_REUSABLE)
// on macOS we try to use MADV_FREE_REUSABLE as it seems the fastest
err = unix_madvise(start, size, MADV_FREE_REUSABLE);
if (err == 0) return 0;
// fall through
#endif
#if defined(MADV_FREE)
// Otherwise, we try to use `MADV_FREE` as that is the fastest. A drawback though is that it
// will not reduce the `rss` stats in tools like `top` even though the memory is available
// to other processes. With the default `MIMALLOC_PURGE_DECOMMITS=1` we ensure that by
// default `MADV_DONTNEED` is used though.
#if defined(MADV_FREE)
static _Atomic(size_t) advice = MI_ATOMIC_VAR_INIT(MADV_FREE);
int oadvice = (int)mi_atomic_load_relaxed(&advice);
int err;
while ((err = unix_madvise(start, size, oadvice)) != 0 && errno == EAGAIN) { errno = 0; };
if (err != 0 && errno == EINVAL && oadvice == MADV_FREE) {
// if MADV_FREE is not supported, fall back to MADV_DONTNEED from now on
@ -469,7 +490,7 @@ int _mi_prim_reset(void* start, size_t size) {
err = unix_madvise(start, size, MADV_DONTNEED);
}
#else
int err = unix_madvise(start, size, MADV_DONTNEED);
err = unix_madvise(start, size, MADV_DONTNEED);
#endif
return err;
}

5
src/prim/wasi/prim.c
View file

@ -149,6 +149,11 @@ int _mi_prim_reset(void* addr, size_t size) {
return 0;
}
int _mi_prim_reuse(void* addr, size_t size) {
MI_UNUSED(addr); MI_UNUSED(size);
return 0;
}
int _mi_prim_protect(void* addr, size_t size, bool protect) {
MI_UNUSED(addr); MI_UNUSED(size); MI_UNUSED(protect);
return 0;

5
src/prim/windows/prim.c
View file

@ -352,6 +352,11 @@ int _mi_prim_reset(void* addr, size_t size) {
return (p != NULL ? 0 : (int)GetLastError());
}
int _mi_prim_reuse(void* addr, size_t size) {
MI_UNUSED(addr); MI_UNUSED(size);
return 0;
}
int _mi_prim_protect(void* addr, size_t size, bool protect) {
DWORD oldprotect = 0;
BOOL ok = VirtualProtect(addr, size, protect ? PAGE_NOACCESS : PAGE_READWRITE, &oldprotect);