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support zero-initialized memory detection

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This commit is contained in:
daan 2019-09-02 13:16:52 -07:00
parent 216d75a222
commit d1bd1644d5
9 changed files with 123 additions and 48 deletions
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57
src/memory.c
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@ -41,10 +41,10 @@ Possible issues:
size_t _mi_os_large_page_size();
bool _mi_os_protect(void* addr, size_t size);
bool _mi_os_unprotect(void* addr, size_t size);
bool _mi_os_commit(void* p, size_t size, mi_stats_t* stats);
bool _mi_os_commit(void* p, size_t size, bool* is_zero, mi_stats_t* stats);
bool _mi_os_decommit(void* p, size_t size, mi_stats_t* stats);
bool _mi_os_reset(void* p, size_t size, mi_stats_t* stats);
bool _mi_os_unreset(void* p, size_t size, mi_stats_t* stats);
bool _mi_os_unreset(void* p, size_t size, bool* is_zero, mi_stats_t* stats);
void* _mi_os_alloc_aligned(size_t size, size_t alignment, bool commit, bool* large, mi_os_tld_t* tld);
void _mi_os_free_ex(void* p, size_t size, bool was_committed, mi_stats_t* stats);
void* _mi_os_try_alloc_from_huge_reserved(size_t size, size_t try_alignment);
@ -86,6 +86,7 @@ static inline void* mi_region_info_read(mi_region_info_t info, bool* is_large, b
typedef struct mem_region_s {
volatile _Atomic(uintptr_t) map; // in-use bit per MI_SEGMENT_SIZE block
volatile _Atomic(mi_region_info_t) info; // start of virtual memory area, and flags
volatile _Atomic(uintptr_t) dirty_mask; // bit per block if the contents are not zero'd
} mem_region_t;
@ -138,7 +139,8 @@ Commit from a region
// Returns `false` on an error (OOM); `true` otherwise. `p` and `id` are only written
// if the blocks were successfully claimed so ensure they are initialized to NULL/SIZE_MAX before the call.
// (not being able to claim is not considered an error so check for `p != NULL` afterwards).
static bool mi_region_commit_blocks(mem_region_t* region, size_t idx, size_t bitidx, size_t blocks, size_t size, bool* commit, bool* allow_large, void** p, size_t* id, mi_os_tld_t* tld)
static bool mi_region_commit_blocks(mem_region_t* region, size_t idx, size_t bitidx, size_t blocks,
size_t size, bool* commit, bool* allow_large, bool* is_zero, void** p, size_t* id, mi_os_tld_t* tld)
{
size_t mask = mi_region_block_mask(blocks,bitidx);
mi_assert_internal(mask != 0);
@ -203,10 +205,19 @@ static bool mi_region_commit_blocks(mem_region_t* region, size_t idx, size_t bit
void* start = mi_region_info_read(info,&region_is_large,&region_is_committed);
mi_assert_internal(!(region_is_large && !*allow_large));
// set dirty bits
uintptr_t m;
do {
m = mi_atomic_read(&region->dirty_mask);
} while (!mi_atomic_cas_weak(&region->dirty_mask, m | mask, m));
*is_zero = ((m & mask) == 0); // no dirty bit set in our claimed range?
void* blocks_start = (uint8_t*)start + (bitidx * MI_SEGMENT_SIZE);
if (*commit && !region_is_committed) {
// ensure commit
_mi_os_commit(blocks_start, mi_good_commit_size(size), tld->stats); // only commit needed size (unless using large OS pages)
// ensure commit
bool commit_zero = false;
_mi_os_commit(blocks_start, mi_good_commit_size(size), &commit_zero, tld->stats); // only commit needed size (unless using large OS pages)
if (commit_zero) *is_zero = true;
}
else if (!*commit && region_is_committed) {
// but even when no commit is requested, we might have committed anyway (in a huge OS page for example)
@ -258,7 +269,8 @@ static inline size_t mi_bsr(uintptr_t x) {
// Returns `false` on an error (OOM); `true` otherwise. `p` and `id` are only written
// if the blocks were successfully claimed so ensure they are initialized to NULL/SIZE_MAX before the call.
// (not being able to claim is not considered an error so check for `p != NULL` afterwards).
static bool mi_region_alloc_blocks(mem_region_t* region, size_t idx, size_t blocks, size_t size, bool* commit, bool* allow_large, void** p, size_t* id, mi_os_tld_t* tld)
static bool mi_region_alloc_blocks(mem_region_t* region, size_t idx, size_t blocks, size_t size,
bool* commit, bool* allow_large, bool* is_zero, void** p, size_t* id, mi_os_tld_t* tld)
{
mi_assert_internal(p != NULL && id != NULL);
mi_assert_internal(blocks < MI_REGION_MAP_BITS);
@ -288,7 +300,8 @@ static bool mi_region_alloc_blocks(mem_region_t* region, size_t idx, size_t bloc
else {
// success, we claimed the bits
// now commit the block memory -- this can still fail
return mi_region_commit_blocks(region, idx, bitidx, blocks, size, commit, allow_large, p, id, tld);
return mi_region_commit_blocks(region, idx, bitidx, blocks,
size, commit, allow_large, is_zero, p, id, tld);
}
}
else {
@ -311,7 +324,9 @@ static bool mi_region_alloc_blocks(mem_region_t* region, size_t idx, size_t bloc
// Returns `false` on an error (OOM); `true` otherwise. `p` and `id` are only written
// if the blocks were successfully claimed so ensure they are initialized to NULL/0 before the call.
// (not being able to claim is not considered an error so check for `p != NULL` afterwards).
static bool mi_region_try_alloc_blocks(size_t idx, size_t blocks, size_t size, bool* commit, bool* allow_large, void** p, size_t* id, mi_os_tld_t* tld)
static bool mi_region_try_alloc_blocks(size_t idx, size_t blocks, size_t size,
bool* commit, bool* allow_large, bool* is_zero,
void** p, size_t* id, mi_os_tld_t* tld)
{
// check if there are available blocks in the region..
mi_assert_internal(idx < MI_REGION_MAX);
@ -331,7 +346,7 @@ static bool mi_region_try_alloc_blocks(size_t idx, size_t blocks, size_t size, b
ok = (start == NULL || (*commit || !is_committed) || (*allow_large || !is_large)); // Todo: test with one bitmap operation?
}
if (ok) {
return mi_region_alloc_blocks(region, idx, blocks, size, commit, allow_large, p, id, tld);
return mi_region_alloc_blocks(region, idx, blocks, size, commit, allow_large, is_zero, p, id, tld);
}
}
return true; // no error, but no success either
@ -343,16 +358,19 @@ static bool mi_region_try_alloc_blocks(size_t idx, size_t blocks, size_t size, b
// Allocate `size` memory aligned at `alignment`. Return non NULL on success, with a given memory `id`.
// (`id` is abstract, but `id = idx*MI_REGION_MAP_BITS + bitidx`)
void* _mi_mem_alloc_aligned(size_t size, size_t alignment, bool* commit, bool* large, size_t* id, mi_os_tld_t* tld)
void* _mi_mem_alloc_aligned(size_t size, size_t alignment, bool* commit, bool* large, bool* is_zero,
size_t* id, mi_os_tld_t* tld)
{
mi_assert_internal(id != NULL && tld != NULL);
mi_assert_internal(size > 0);
*id = SIZE_MAX;
*is_zero = false;
bool default_large = false;
if (large==NULL) large = &default_large; // ensure `large != NULL`
if (large==NULL) large = &default_large; // ensure `large != NULL`
// use direct OS allocation for huge blocks or alignment (with `id = SIZE_MAX`)
if (size > MI_REGION_MAX_ALLOC_SIZE || alignment > MI_SEGMENT_ALIGN) {
*is_zero = true;
return _mi_os_alloc_aligned(mi_good_commit_size(size), alignment, *commit, large, tld); // round up size
}
@ -370,20 +388,21 @@ void* _mi_mem_alloc_aligned(size_t size, size_t alignment, bool* commit, bool* l
size_t idx = 0; // tld->region_idx; // start at 0 to reuse low addresses? Or, use tld->region_idx to reduce contention?
for (size_t visited = 0; visited < count; visited++, idx++) {
if (idx >= count) idx = 0; // wrap around
if (!mi_region_try_alloc_blocks(idx, blocks, size, commit, large, &p, id, tld)) return NULL; // error
if (!mi_region_try_alloc_blocks(idx, blocks, size, commit, large, is_zero, &p, id, tld)) return NULL; // error
if (p != NULL) break;
}
if (p == NULL) {
// no free range in existing regions -- try to extend beyond the count.. but at most 4 regions
for (idx = count; idx < count + 4 && idx < MI_REGION_MAX; idx++) {
if (!mi_region_try_alloc_blocks(idx, blocks, size, commit, large, &p, id, tld)) return NULL; // error
if (!mi_region_try_alloc_blocks(idx, blocks, size, commit, large, is_zero, &p, id, tld)) return NULL; // error
if (p != NULL) break;
}
}
if (p == NULL) {
// we could not find a place to allocate, fall back to the os directly
*is_zero = true;
p = _mi_os_alloc_aligned(size, alignment, commit, large, tld);
}
else {
@ -439,8 +458,8 @@ void _mi_mem_free(void* p, size_t size, size_t id, mi_stats_t* stats) {
// reset: 10x slowdown on malloc-large, decommit: 17x slowdown on malloc-large
if (!is_large) {
if (mi_option_is_enabled(mi_option_segment_reset)) {
_mi_os_reset(p, size, stats);
// _mi_os_decommit(p,size,stats); // if !is_eager_committed
_mi_os_reset(p, size, stats); //
// _mi_os_decommit(p,size,stats); // if !is_eager_committed (and clear dirty bits)
}
// else { _mi_os_reset(p,size,stats); }
}
@ -495,8 +514,8 @@ void _mi_mem_collect(mi_stats_t* stats) {
Other
-----------------------------------------------------------------------------*/
bool _mi_mem_commit(void* p, size_t size, mi_stats_t* stats) {
return _mi_os_commit(p, size, stats);
bool _mi_mem_commit(void* p, size_t size, bool* is_zero, mi_stats_t* stats) {
return _mi_os_commit(p, size, is_zero, stats);
}
bool _mi_mem_decommit(void* p, size_t size, mi_stats_t* stats) {
@ -507,8 +526,8 @@ bool _mi_mem_reset(void* p, size_t size, mi_stats_t* stats) {
return _mi_os_reset(p, size, stats);
}
bool _mi_mem_unreset(void* p, size_t size, mi_stats_t* stats) {
return _mi_os_unreset(p, size, stats);
bool _mi_mem_unreset(void* p, size_t size, bool* is_zero, mi_stats_t* stats) {
return _mi_os_unreset(p, size, is_zero, stats);
}
bool _mi_mem_protect(void* p, size_t size) {