We are in a bit of a quandary here with some memory issues surrounding our application. This is a multitasking LE C application running in 31 bit mode that utilizes the IBM JSON and EZNOSQL Services. Some of the attributes are:
• z/OS V2.5 Operation System • POSIX(OFF) - all tasks/subtasks • Single address space (31 Bit Mode) • ATTACHX Multi-tasking model (no pthreads) • Execute as started task – Problem State – Key 4 • Drop in/out of supervisor state as needed • 3 EZNOSQL Databases are opened at application start and remain open until termination • Open EZNOSQL connections tokens are passed to the worker task(s) along with the unit of work to be processed Our issue is that the total available heap grows until we end up exhausting all available memory and inevitable application failure, but the key here is that while the total heap grows with every unit of work processed by tasks, the in use amount only shows no or only a small (<128 bytes) increment between units of work. For example, here is a heap report (using LE __heaprpt function) example. So we are fairly confident that our application code is not leaking memory. HeapReport: ZdpQuery @Start - Total/In Use/Available: 1048576/ 888160/ 160416. HeapReport: ZdpQuery @Enter - Total/In Use/Available: 1048576/ 888160/ 160416. HeapReport: ZdpQuery @Exit - Total/In Use/Available: 1560856/ 888192/ 672664. HeapReport: ZdpQuery @Enter - Total/In Use/Available: 1560856/ 888192/ 672664. HeapReport: ZdpQuery @Exit - Total/In Use/Available: 2073088/ 888224/ 1184864. HeapReport: ZdpQuery @Enter - Total/In Use/Available: 2073088/ 888224/ 1184864. HeapReport: ZdpQuery @Exit - Total/In Use/Available: 2073088/ 888224/ 1184864. HeapReport: ZdpQuery @Enter - Total/In Use/Available: 2073088/ 888224/ 1184864. HeapReport: ZdpQuery @Exit - Total/In Use/Available: 2585376/ 888256/ 1697120. HeapReport: ZdpQuery @Enter - Total/In Use/Available: 2585376/ 888256/ 1697120. HeapReport: ZdpQuery @Exit - Total/In Use/Available: 2585376/ 888256/ 1697120. HeapReport: ZdpQuery @Enter - Total/In Use/Available: 2585376/ 888256/ 1697120. HeapReport: ZdpQuery @Exit - Total/In Use/Available: 2585376/ 888256/ 1697120. HeapReport: ZdpQuery @Finish - Total/In Use/Available: 2585376/ 888256/ 1697120. The @Start and @Finish lines show the heap report results just after the task is attached and before it terminates. Each of the @Enter/@Exit lines show the heap at the unit of work start and end processing, respectively. We are at a loss to explain why the heap keeps growing. We would expect that the heap would grow to some high water mark and become stabilized, but the total size just keeps growing until the application fails due to out of memory condition, even though there is a significant amount of heap storage available. Our tasks are returning all the storage they directly allocate back to the heap, as indicated by in use at start & end. While there is a small increment in the in use number, we think that may just be LE overhead in managing the heap, but in any case is generally less than 128 bytes per iteration, and only appears then the total heap size increases. What makes this example even more interesting, is that we are processing the exact same request for each iteration. We’ve turned on all the various LE memory analysis options (HEAPCHK, RPTSTG) and utilized the LE alternate heap manager to detect overlays, corruption, etc.. This pointed us to a couple of minor leaks we plugged but has not led us to an answer as to the growing heap. We make heavy use of the IBM JSON and EZNOSQL services during processing. We are in search of any insight, recommendations as to how to proceed in diagnosis this issue. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
