Skip to content

Fix GH-13193: Significant performance degradation in 'foreach' starting from PHP 8.2.13 (caused by garbage collection) #13265

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Jan 30, 2024
Merged

Fix GH-13193: Significant performance degradation in 'foreach' starting from PHP 8.2.13 (caused by garbage collection) #13265

Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
e0bdde0
Fix GH-13193: Significant performance degradation in 'foreach' starti…
dstogov Jan 29, 2024
a7559de
Don't run zend_gc_remove_root_tmpvars() if GC is not active or GC buf…
dstogov Jan 29, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
39 changes: 36 additions & 3 deletions Zend/zend_gc.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1465,14 +1465,17 @@ static int gc_remove_nested_data_from_buffer(zend_refcounted *ref, gc_root_buffe
}

static void zend_get_gc_buffer_release(void);
static void zend_gc_root_tmpvars(void);
static void zend_gc_check_root_tmpvars(void);
static void zend_gc_remove_root_tmpvars(void);

ZEND_API int zend_gc_collect_cycles(void)
{
int total_count = 0;
bool should_rerun_gc = 0;
bool did_rerun_gc = 0;

zend_gc_remove_root_tmpvars();
Copy link
Member

@iluuu1994 iluuu1994 Jan 29, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can this be moved into the if below? Preferably after if (GC_G(gc_active)) { so that this doesn't run twice when GC isn't even active.

Edit: It would only run once since the check returns. Might be fine if it can remove some elements from the buffer I suppose.

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

It make sense to wrap this call with if (GC(active) && GC_G(num_roots)).
Moving the call down is not a good idea because of rerun_gc label.


rerun_gc:
if (GC_G(num_roots)) {
int count;
Expand Down Expand Up @@ -1669,7 +1672,7 @@ ZEND_API int zend_gc_collect_cycles(void)

finish:
zend_get_gc_buffer_release();
zend_gc_root_tmpvars();
zend_gc_check_root_tmpvars();
return total_count;
}

Expand Down Expand Up @@ -1707,7 +1710,7 @@ static void zend_get_gc_buffer_release(void) {
* cycles. However, there are some rare exceptions where this is possible, in which case we rely
* on the producing code to root the value. If a GC run occurs between the rooting and consumption
* of the value, we would end up leaking it. To avoid this, root all live TMPVAR values here. */
static void zend_gc_root_tmpvars(void) {
static void zend_gc_check_root_tmpvars(void) {
zend_execute_data *ex = EG(current_execute_data);
for (; ex; ex = ex->prev_execute_data) {
zend_function *func = ex->func;
Expand Down Expand Up @@ -1737,6 +1740,36 @@ static void zend_gc_root_tmpvars(void) {
}
}

static void zend_gc_remove_root_tmpvars(void) {
zend_execute_data *ex = EG(current_execute_data);
for (; ex; ex = ex->prev_execute_data) {
zend_function *func = ex->func;
if (!func || !ZEND_USER_CODE(func->type)) {
continue;
}

uint32_t op_num = ex->opline - ex->func->op_array.opcodes;
for (uint32_t i = 0; i < func->op_array.last_live_range; i++) {
const zend_live_range *range = &func->op_array.live_range[i];
if (range->start > op_num) {
break;
}
if (range->end <= op_num) {
continue;
}

uint32_t kind = range->var & ZEND_LIVE_MASK;
if (kind == ZEND_LIVE_TMPVAR || kind == ZEND_LIVE_LOOP) {
uint32_t var_num = range->var & ~ZEND_LIVE_MASK;
zval *var = ZEND_CALL_VAR(ex, var_num);
if (Z_REFCOUNTED_P(var)) {
GC_REMOVE_FROM_BUFFER(Z_COUNTED_P(var));
}
}
}
}
}

#ifdef ZTS
size_t zend_gc_globals_size(void)
{
Expand Down