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malloc: Keep some stats and dump them at process exit if LIBC_DUMP_MALLOC_STATS is set

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Very bare-bones and barely useful. Can go away once the perf_event-based
malloc tracking is further along.
This commit is contained in:
Nico Weber 2020-08-16 21:24:14 -04:00 committed by Andreas Kling
parent c44d2515b4
commit 22f701d657
Notes: sideshowbarker 2024-07-19 03:30:03 +09:00 
Author: https://github.com/nico
Commit: https://github.com/SerenityOS/serenity/commit/22f701d6570
Pull-request: https://github.com/SerenityOS/serenity/pull/3186
3 changed files with 72 additions and 2 deletions
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69
Libraries/LibC/malloc.cpp
View file

@ -25,6 +25,7 @@
*/
#include <AK/InlineLinkedList.h>
#include <AK/LogStream.h>
#include <AK/ScopedValueRollback.h>
#include <AK/Vector.h>
#include <LibThread/Lock.h>
@ -72,6 +73,29 @@ static bool s_profiling = false;
static unsigned short size_classes[] = { 8, 16, 32, 64, 128, 252, 508, 1016, 2036, 4090, 8188, 16376, 32756, 0 };
static constexpr size_t num_size_classes = sizeof(size_classes) / sizeof(unsigned short);
struct MallocStats {
size_t number_of_malloc_calls;
size_t number_of_big_allocator_hits;
size_t number_of_big_allocator_purge_hits;
size_t number_of_big_allocs;
size_t number_of_empty_block_hits;
size_t number_of_empty_block_purge_hits;
size_t number_of_block_allocs;
size_t number_of_blocks_full;
size_t number_of_free_calls;
size_t number_of_big_allocator_keeps;
size_t number_of_big_allocator_frees;
size_t number_of_freed_full_blocks;
size_t number_of_keeps;
size_t number_of_frees;
};
static MallocStats g_malloc_stats = {};
constexpr size_t block_size = 64 * KiB;
constexpr size_t block_mask = ~(block_size - 1);
@ -207,6 +231,8 @@ static void* malloc_impl(size_t size)
if (!size)
return nullptr;
g_malloc_stats.number_of_malloc_calls++;
size_t good_size;
auto* allocator = allocator_for_size(size, good_size);
@ -215,6 +241,7 @@ static void* malloc_impl(size_t size)
#ifdef RECYCLE_BIG_ALLOCATIONS
if (auto* allocator = big_allocator_for_size(real_size)) {
if (!allocator->blocks.is_empty()) {
g_malloc_stats.number_of_big_allocator_hits++;
auto* block = allocator->blocks.take_last();
int rc = madvise(block, real_size, MADV_SET_NONVOLATILE);
bool this_block_was_purged = rc == 1;
@ -226,14 +253,17 @@ static void* malloc_impl(size_t size)
perror("mprotect");
ASSERT_NOT_REACHED();
}
if (this_block_was_purged)
if (this_block_was_purged) {
g_malloc_stats.number_of_big_allocator_purge_hits++;
new (block) BigAllocationBlock(real_size);
}
ue_notify_malloc(&block->m_slot[0], size);
return &block->m_slot[0];
}
}
#endif
g_malloc_stats.number_of_big_allocs++;
auto* block = (BigAllocationBlock*)os_alloc(real_size, "malloc: BigAllocationBlock");
new (block) BigAllocationBlock(real_size);
ue_notify_malloc(&block->m_slot[0], size);
@ -248,6 +278,7 @@ static void* malloc_impl(size_t size)
}
if (!block && allocator->empty_block_count) {
g_malloc_stats.number_of_empty_block_hits++;
block = allocator->empty_blocks[--allocator->empty_block_count];
int rc = madvise(block, block_size, MADV_SET_NONVOLATILE);
bool this_block_was_purged = rc == 1;
@ -260,12 +291,15 @@ static void* malloc_impl(size_t size)
perror("mprotect");
ASSERT_NOT_REACHED();
}
if (this_block_was_purged)
if (this_block_was_purged) {
g_malloc_stats.number_of_empty_block_purge_hits++;
new (block) ChunkedBlock(good_size);
}
allocator->usable_blocks.append(block);
}
if (!block) {
g_malloc_stats.number_of_block_allocs++;
char buffer[64];
snprintf(buffer, sizeof(buffer), "malloc: ChunkedBlock(%zu)", good_size);
block = (ChunkedBlock*)os_alloc(block_size, buffer);
@ -278,6 +312,7 @@ static void* malloc_impl(size_t size)
void* ptr = block->m_freelist;
block->m_freelist = block->m_freelist->next;
if (block->is_full()) {
g_malloc_stats.number_of_blocks_full++;
#ifdef MALLOC_DEBUG
dbgprintf("Block %p is now full in size class %zu\n", block, good_size);
#endif
@ -302,6 +337,8 @@ static void free_impl(void* ptr)
if (!ptr)
return;
g_malloc_stats.number_of_free_calls++;
LOCKER(malloc_lock());
void* block_base = (void*)((FlatPtr)ptr & block_mask);
@ -312,6 +349,7 @@ static void free_impl(void* ptr)
#ifdef RECYCLE_BIG_ALLOCATIONS
if (auto* allocator = big_allocator_for_size(block->m_size)) {
if (allocator->blocks.size() < number_of_big_blocks_to_keep_around_per_size_class) {
g_malloc_stats.number_of_big_allocator_keeps++;
allocator->blocks.append(block);
size_t this_block_size = block->m_size;
if (mprotect(block, this_block_size, PROT_NONE) < 0) {
@ -326,6 +364,7 @@ static void free_impl(void* ptr)
}
}
#endif
g_malloc_stats.number_of_big_allocator_frees++;
os_free(block, block->m_size);
return;
}
@ -350,6 +389,7 @@ static void free_impl(void* ptr)
#ifdef MALLOC_DEBUG
dbgprintf("Block %p no longer full in size class %u\n", block, good_size);
#endif
g_malloc_stats.number_of_freed_full_blocks++;
allocator->full_blocks.remove(block);
allocator->usable_blocks.prepend(block);
}
@ -363,6 +403,7 @@ static void free_impl(void* ptr)
#ifdef MALLOC_DEBUG
dbgprintf("Keeping block %p around for size class %u\n", block, good_size);
#endif
g_malloc_stats.number_of_keeps++;
allocator->usable_blocks.remove(block);
allocator->empty_blocks[allocator->empty_block_count++] = block;
mprotect(block, block_size, PROT_NONE);
@ -372,6 +413,7 @@ static void free_impl(void* ptr)
#ifdef MALLOC_DEBUG
dbgprintf("Releasing block %p for size class %u\n", block, good_size);
#endif
g_malloc_stats.number_of_frees++;
allocator->usable_blocks.remove(block);
--allocator->block_count;
os_free(block, block_size);
@ -454,4 +496,27 @@ void __malloc_init()
new (&big_allocators()[0])(BigAllocator);
}
void serenity_dump_malloc_stats()
{
dbg() << "# malloc() calls: " << g_malloc_stats.number_of_malloc_calls;
dbg();
dbg() << "big alloc hits: " << g_malloc_stats.number_of_big_allocator_hits;
dbg() << "big alloc hits that were purged: " << g_malloc_stats.number_of_big_allocator_purge_hits;
dbg() << "big allocs: " << g_malloc_stats.number_of_big_allocs;
dbg();
dbg() << "empty block hits: " << g_malloc_stats.number_of_empty_block_hits;
dbg() << "empty block hits that were purged: " << g_malloc_stats.number_of_empty_block_purge_hits;
dbg() << "block allocs: " << g_malloc_stats.number_of_block_allocs;
dbg() << "filled blocks: " << g_malloc_stats.number_of_blocks_full;
dbg();
dbg() << "# free() calls: " << g_malloc_stats.number_of_free_calls;
dbg();
dbg() << "big alloc keeps: " << g_malloc_stats.number_of_big_allocator_keeps;
dbg() << "big alloc frees: " << g_malloc_stats.number_of_big_allocator_frees;
dbg();
dbg() << "full block frees: " << g_malloc_stats.number_of_freed_full_blocks;
dbg() << "number of keeps: " << g_malloc_stats.number_of_keeps;
dbg() << "number of frees: " << g_malloc_stats.number_of_frees;
}
}

4
Libraries/LibC/stdlib.cpp
View file

@ -201,6 +201,10 @@ extern "C" {
void exit(int status)
{
__cxa_finalize(nullptr);
if (getenv("LIBC_DUMP_MALLOC_STATS"))
serenity_dump_malloc_stats();
extern void _fini();
_fini();
fflush(stdout);

1
Libraries/LibC/stdlib.h
View file

@ -41,6 +41,7 @@ __BEGIN_DECLS
__attribute__((malloc)) __attribute__((alloc_size(1))) void* malloc(size_t);
__attribute__((malloc)) __attribute__((alloc_size(1, 2))) void* calloc(size_t nmemb, size_t);
size_t malloc_size(void*);
void serenity_dump_malloc_stats(void);
void free(void*);
__attribute__((alloc_size(2))) void* realloc(void* ptr, size_t);
char* getenv(const char* name);