Bug #70098 [Opn->Asn]: Real memory usage doesn't decrease

Edit report at https://bugs.php.net/bug.php?id=70098&edit=1 ID: 70098 Updated by: bwoebi@php.net Reported by: robin dot kunde at recoursive dot com Summary: Real memory usage doesn't decrease -Status: Open +Status: Assigned Type: Bug Package: Performance problem Operating System: Ubuntu 15.04, OSX 10.10.4 PHP Version: 7.0.0beta1 -Assigned To: +Assigned To: dmitry Block user comment: N Private report: N New Comment: PHP 7 uses a new memory allocator, which puts small allocations of 3 KB or less into buckets with well defined sizes. These small buckets though… are never freed. @Dmitry: Is that intentional that they're never freed? I see no handling logic for unmmapping these... Sure, it's faster to not have logic which frees them, but seems we need it. Previous Comments: ------------------------------------------------------------------------ [2015-07-18 20:43:38] robin dot kunde at recoursive dot com Description: ------------ PHP 7b1 doesn't appear to be reclaiming freed memory correctly. This problem only affects real usage as reported by memory_get_usage(true). Usage as reported by memory_get_usage(false) behaves as expected. The problem appears to be related to allocation of strings, the use of stdclass, and/or multidimensional array. I don't believe PHP is actually leaking memory, since usage is not continuously increasing. It just appear that certain actions prevent real usage from decreasing again after variables are nulled out or leave scope. The test script gist I posted can demonstrates the problem better than I can explain it. This problem still occurs with the master git branch as of 7/17. Test script: --------------- https://gist.github.com/robinkunde/68f3d442aa294550ab15 Expected result: ---------------- PHP 5.6.11 Assembling 5M string Real: 0.50, Malloc: 0.25 Storing 1M bools Real: 0.75, Malloc: 0.25 Real: 1.00, Malloc: 0.25 Real: 1.00, Malloc: 0.25 Storing 1M ints Real: 1.25, Malloc: 0.25 Real: 1.25, Malloc: 0.25 Real: 1.50, Malloc: 0.25 Storing 1M stringyfied ints Real: 1.50, Malloc: 0.25 Real: 1.75, Malloc: 0.25 Real: 1.75, Malloc: 0.25 Storing 1M stringyfied ints with stringyfied int keys Real: 1.75, Malloc: 0.25 Real: 1.75, Malloc: 0.25 Real: 1.75, Malloc: 0.25 Storing 1M empty strings Real: 1.75, Malloc: 0.25 Real: 2.00, Malloc: 0.25 Real: 2.00, Malloc: 0.25 Storing 1M hellos Real: 2.00, Malloc: 0.25 Real: 2.25, Malloc: 0.25 Real: 2.00, Malloc: 0.25 Storing 1M hellos with stringyfied int keys Real: 2.00, Malloc: 0.25 Storing 1M empty arrays Real: 1.50, Malloc: 0.25 Real: 2.00, Malloc: 0.25 Real: 2.00, Malloc: 0.25 Storing 1M arrays with empty strings Real: 2.00, Malloc: 0.25 Real: 2.50, Malloc: 0.25 Real: 2.50, Malloc: 0.25 Storing 1M arrays with hello Real: 2.50, Malloc: 0.25 Real: 2.75, Malloc: 0.25 Real: 2.75, Malloc: 0.25 Final Usage Real: 2.75, Malloc: 0.25 Real peak: 436.00, Malloc peak: 435.50 Actual result: -------------- PHP 7.0.0b1 Assembling 5M string Real: 4.00, Malloc: 0.36 Storing 1M bools Real: 4.00, Malloc: 0.36 Real: 32.00, Malloc: 0.36 Real: 32.00, Malloc: 0.36 Storing 1M ints Real: 32.00, Malloc: 0.36 Real: 32.00, Malloc: 0.36 Real: 32.00, Malloc: 0.36 Storing 1M stringyfied ints Real: 32.00, Malloc: 0.36 Real: 62.00, Malloc: 0.36 Real: 62.00, Malloc: 0.36 Storing 1M stringyfied ints with stringyfied int keys Real: 62.00, Malloc: 0.36 Real: 62.00, Malloc: 0.36 Real: 62.00, Malloc: 0.36 Storing 1M empty strings Real: 62.00, Malloc: 0.36 Real: 62.00, Malloc: 0.36 Real: 62.00, Malloc: 0.36 Storing 1M hellos Real: 62.00, Malloc: 0.36 Real: 62.00, Malloc: 0.36 Real: 62.00, Malloc: 0.36 Storing 1M hellos with stringyfied int keys Real: 62.00, Malloc: 0.36 Storing 1M empty arrays Real: 116.00, Malloc: 0.36 Real: 116.00, Malloc: 0.36 Real: 116.00, Malloc: 0.36 Storing 1M arrays with empty strings Real: 422.00, Malloc: 0.36 Real: 422.00, Malloc: 0.36 Real: 422.00, Malloc: 0.36 Storing 1M arrays with hello Real: 422.00, Malloc: 0.36 Real: 422.00, Malloc: 0.36 Real: 422.00, Malloc: 0.36 Final Usage Real: 422.00, Malloc: 0.36 Real peak: 476.00, Malloc peak: 425.46 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=70098&edit=1