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LibC: Make empty malloc blocks purgeable

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This commit is contained in:
Sergey Bugaev 2019-12-17 23:01:19 +03:00 • committed by Andreas Kling
parent ac007218bc
commit d91c40de3b
1 changed files with 23 additions and 2 deletions
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25
Libraries/LibC/malloc.cpp
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@ -134,7 +134,7 @@ size_t malloc_good_size(size_t size)
static void* os_alloc(size_t size, const char* name) static void* os_alloc(size_t size, const char* name)
{ {
return mmap_with_name(nullptr, size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0, name); return mmap_with_name(nullptr, size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_PURGEABLE, 0, 0, name);
} }
static void os_free(void* ptr, size_t size) static void os_free(void* ptr, size_t size)
@ -162,10 +162,18 @@ void* malloc(size_t size)
if (auto* allocator = big_allocator_for_size(real_size)) { if (auto* allocator = big_allocator_for_size(real_size)) {
if (!allocator->blocks.is_empty()) { if (!allocator->blocks.is_empty()) {
auto* block = allocator->blocks.take_last(); auto* block = allocator->blocks.take_last();
int rc = madvise(block, real_size, MADV_SET_NONVOLATILE);
bool this_block_was_purged = rc == 1;
if (rc < 0) {
perror("madvise");
ASSERT_NOT_REACHED();
}
if (mprotect(block, real_size, PROT_READ | PROT_WRITE) < 0) { if (mprotect(block, real_size, PROT_READ | PROT_WRITE) < 0) {
perror("mprotect"); perror("mprotect");
ASSERT_NOT_REACHED(); ASSERT_NOT_REACHED();
} }
if (this_block_was_purged)
new (block) BigAllocationBlock(real_size);
set_mmap_name(block, PAGE_SIZE, "malloc: BigAllocationBlock (reused)"); set_mmap_name(block, PAGE_SIZE, "malloc: BigAllocationBlock (reused)");
return &block->m_slot[0]; return &block->m_slot[0];
} }
@ -185,11 +193,19 @@ void* malloc(size_t size)
if (!block && allocator->empty_block_count) { if (!block && allocator->empty_block_count) {
block = allocator->empty_blocks[--allocator->empty_block_count]; block = allocator->empty_blocks[--allocator->empty_block_count];
int rc = mprotect(block, PAGE_SIZE, PROT_READ | PROT_WRITE); int rc = madvise(block, PAGE_SIZE, MADV_SET_NONVOLATILE);
bool this_block_was_purged = rc == 1;
if (rc < 0) {
perror("madvise");
ASSERT_NOT_REACHED();
}
rc = mprotect(block, PAGE_SIZE, PROT_READ | PROT_WRITE);
if (rc < 0) { if (rc < 0) {
perror("mprotect"); perror("mprotect");
ASSERT_NOT_REACHED(); ASSERT_NOT_REACHED();
} }
if (this_block_was_purged)
new (block) ChunkedBlock(good_size);
char buffer[64]; char buffer[64];
snprintf(buffer, sizeof(buffer), "malloc: ChunkedBlock(%zu) (reused)", good_size); snprintf(buffer, sizeof(buffer), "malloc: ChunkedBlock(%zu) (reused)", good_size);
set_mmap_name(block, PAGE_SIZE, buffer); set_mmap_name(block, PAGE_SIZE, buffer);
@ -246,6 +262,10 @@ void free(void* ptr)
perror("mprotect"); perror("mprotect");
ASSERT_NOT_REACHED(); ASSERT_NOT_REACHED();
} }
if (madvise(block, PAGE_SIZE, MADV_SET_VOLATILE) != 0) {
perror("madvise");
ASSERT_NOT_REACHED();
}
return; return;
} }
} }
@ -293,6 +313,7 @@ void free(void* ptr)
snprintf(buffer, sizeof(buffer), "malloc: ChunkedBlock(%zu) (free)", good_size); snprintf(buffer, sizeof(buffer), "malloc: ChunkedBlock(%zu) (free)", good_size);
set_mmap_name(block, PAGE_SIZE, buffer); set_mmap_name(block, PAGE_SIZE, buffer);
mprotect(block, PAGE_SIZE, PROT_NONE); mprotect(block, PAGE_SIZE, PROT_NONE);
madvise(block, PAGE_SIZE, MADV_SET_VOLATILE);
return; return;
} }
#ifdef MALLOC_DEBUG #ifdef MALLOC_DEBUG