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revise unix decommit

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This commit is contained in:
daanx 2023-04-23 20:53:27 -07:00
parent bfe2651ec9
commit 88a8b13782
1 changed files with 21 additions and 11 deletions
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32
src/prim/unix/prim.c
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@ -357,26 +357,36 @@ static void unix_mprotect_hint(int err) {
int _mi_prim_commit(void* start, size_t size, bool* is_zero) { int _mi_prim_commit(void* start, size_t size, bool* is_zero) {
// commit: ensure we can access the area // commit: ensure we can access the area
*is_zero = false; // note: we may think that *is_zero can be true since the memory
// was either from mmap PROT_NONE, or from decommit MADV_DONTNEED, but
// we sometimes call commit on a range with still partially committed
// memory and `mprotect` does not zero the range.
*is_zero = false;
int err = mprotect(start, size, (PROT_READ | PROT_WRITE)); int err = mprotect(start, size, (PROT_READ | PROT_WRITE));
if (err != 0) { err = errno; } if (err != 0) {
unix_mprotect_hint(err); err = errno;
unix_mprotect_hint(err);
}
return err; return err;
} }
int _mi_prim_decommit(void* start, size_t size, bool* needs_recommit) { int _mi_prim_decommit(void* start, size_t size, bool* needs_recommit) {
int err = 0; int err = 0;
#if defined(MADV_DONTNEED) && !MI_DEBUG && !MI_SECURE // decommit: use MADV_DONTNEED as it decreases rss immediately (unlike MADV_FREE)
// decommit: use MADV_DONTNEED as it decreases rss immediately (unlike MADV_FREE) err = unix_madvise(start, size, MADV_DONTNEED);
#if !MI_DEBUG && !MI_SECURE
*needs_recommit = false; *needs_recommit = false;
err = unix_madvise(start, size, MADV_DONTNEED);
#else #else
// decommit: use mmap with MAP_FIXED and PROT_NONE to discard the existing memory (and reduce rss)
*needs_recommit = true; *needs_recommit = true;
const int fd = unix_mmap_fd(); mprotect(start, size, PROT_NONE);
void* p = mmap(start, size, PROT_NONE, (MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE), fd, 0);
if (p != start) { err = errno; }
#endif #endif
/*
// decommit: use mmap with MAP_FIXED and PROT_NONE to discard the existing memory (and reduce rss)
*needs_recommit = true;
const int fd = unix_mmap_fd();
void* p = mmap(start, size, PROT_NONE, (MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE), fd, 0);
if (p != start) { err = errno; }
*/
return err; return err;
} }