Bug #80447 [Opn->Ver]: Strange out of memory error when running with JIT
Edit report at https://bugs.php.net/bug.php?id=80447&edit=1
ID: 80447
Updated by: nikic@php.net
Reported by: dac514 at hotmail dot com
Summary: Strange out of memory error when running with JIT
-Status: Open
+Status: Verified
Type: Bug
Package: JIT
Operating System: Ubuntu
PHP Version: 8.0.0
-Assigned To:
+Assigned To: dmitry
Block user comment: N
Private report: N
Previous Comments:
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[2020-11-30 20:23:19] dac514 at hotmail dot com
Upstream ticket: https://salsa.debian.org/benchmarksgame-team/benchmarksgame/-/issues/401
------------------------------------------------------------------------
[2020-11-30 20:21:49] dac514 at hotmail dot com
Description:
------------
In the last few days benchmarksgame-team.pages.debian.net upgraded to PHP8.
This script;
https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/binarytrees-php-4.html
When run with JIT:
/opt/src/php-8.0.0/bin/php
-dzend_extension=/opt/src/php-8.0.0/lib/php/extensions/no-debug-non-zts-20200930/opcache.so
-dopcache.enable_cli=1 -dopcache.jit_buffer_size=64M -n -d memory_limit=4096M binarytrees.php-4.php
21
Runs out of memory, very unusually, (it did not run out of memory in previous versions of PHP)
The following weird hack is a workaround, change:
```
function createTree($depth)
{
if (!$depth) {
return [null, null];
```
To:
```
function createTree($depth)
{
echo '';
if (!$depth) {
return [null, null];
```
I don't get it?
Test script:
---------------
function createTree($depth)
{
// echo ''; // TODO: This hack works?!
if (!$depth) {
return [null, null];
}
$depth--;
return [
createTree($depth),
createTree($depth)
];
}
function checkTree($treeNode)
{
return 1
+ ($treeNode[0][0] === null ? 1 : checkTree($treeNode[0]))
+ ($treeNode[1][0] === null ? 1 : checkTree($treeNode[1]));
}
$minDepth = 4;
$n = ($argc == 2) ? $argv[1] : 1;
$maxDepth = max($minDepth + 2, $n);
$stretchDepth = $maxDepth + 1;
$stretchTree = createTree($stretchDepth);
echo "stretch tree of depth $stretchDepth\t check: ", checkTree($stretchTree), PHP_EOL;
unset($stretchTree);
$longLivedTree = createTree($maxDepth);
function startWorker($depth, $iter, $n, $size, $shmId)
{
$pid = pcntl_fork();
if ($pid) {
return $pid;
} else {
$check = 0;
for ($i = 1; $i <= $iter; ++$i) {
$t = createTree($depth);
$check += checkTree($t);
unset($t);
}
$result = "$iter\t trees of depth $depth\t check: $check\n";
shmop_write($shmId, $result, $size * ($n - 1));
exit(0);
}
}
$iterations = 1 << ($maxDepth);
$depthIterations = [$minDepth => $iterations];
do {
$minDepth += 2;
if ($minDepth <= $maxDepth) {
$iterations >>= 2;
$depthIterations[$minDepth] = $iterations;
}
} while ($minDepth <= $maxDepth);
extension_loaded('shmop') or dl('shmop.so');
$size = 128;
$shmId = shmop_open(ftok(__FILE__, 'b'), 'c', 0644, $size *
(count($depthIterations) + 1));
$PIDs = [];
$n = 0;
foreach ($depthIterations as $d => $i) {
$PIDs[] = startWorker($d, $i, ++$n, $size, $shmId);
}
foreach ($PIDs as $PID) {
pcntl_waitpid($PID, $status);
}
foreach (range(1, count($depthIterations)) as $n) {
echo trim(shmop_read($shmId, $size * ($n - 1), $size)), PHP_EOL;
}
shmop_delete($shmId);
echo "long lived tree of depth $maxDepth\t check: ", checkTree($longLivedTree), PHP_EOL;
Expected result:
----------------
PROGRAM OUTPUT:
stretch tree of depth 22 check: 8388607
2097152 trees of depth 4 check: 65011712
524288 trees of depth 6 check: 66584576
131072 trees of depth 8 check: 66977792
32768 trees of depth 10 check: 67076096
8192 trees of depth 12 check: 67100672
2048 trees of depth 14 check: 67106816
512 trees of depth 16 check: 67108352
128 trees of depth 18 check: 67108736
32 trees of depth 20 check: 67108832
long lived tree of depth 21 check: 4194303
Actual result:
--------------
Out of memory error. Terminated.
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--
Edit this bug report at https://bugs.php.net/bug.php?id=80447&edit=1
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