.Net CLR Memory Performance Monitoring

If you need to monitor you memory the usage of Perfmon is needed to start. There are also some shareware and MS CLR Profiler available but lets explain the basic's for the usage of Perfmon.

to start perfmon: start -> run: type: perfmon and the Performance SnapIn window appears.



the window starts with some default counters, usually you those are not the counters you will have to look on. Therefor you need to choose the right selection, which you do with right click -> add counters. Then you can select your requested counters as shown below:




Lets describe the different counters we have:

• # Bytes in all Heaps: This counter is the sum of four other counters; Gen 0 Heap Size; Gen 1 Heap Size; Gen 2 Heap Size and the Large Object Heap Size. This counter indicates the current memory allocated in bytes on the GC Heaps.
• # GC Handles: This counter displays the current number of GC Handles in use. GCHandles are handles to resources external to the CLR and the managed environment. Handles occupy small amounts of memory in the GCHeap but potentially expensive unmanaged resources.
• # Gen 0 Collections: This counter displays the number of times the generation 0 objects (youngest; most recently allocated) are garbage collected (Gen 0 GC) since the start of the application. Gen 0 GC occurs when the available memory in generation 0 is not sufficient to satisfy an allocation request. This counter is incremented at the end of a Gen 0 GC. Higher generation GCs include all lower generation GCs. This counter is explicitly incremented when a higher generation (Gen 1 or Gen 2) GC occurs. _Global_ counter value is not accurate and should be ignored. This counter displays the last observed value.
• # Gen 1 Collections: This counter displays the number of times the generation 1 objects are garbage collected since the start of the application. The counter is incremented at the end of a Gen 1 GC. Higher generation GCs include all lower generation GCs. This counter is explicitly incremented when a higher generation (Gen 2) GC occurs. _Global_ counter value is not accurate and should be ignored. This counter displays the last observed value.
• # Gen 2 Collections: This counter displays the number of times the generation 2 objects (older) are garbage collected since the start of the application. The counter is incremented at the end of a Gen 2 GC (also called full GC). _Global_ counter value is not accurate and should be ignored. This counter displays the last observed value.
• # Induced GC: This counter displays the peak number of times a garbage collection was performed because of an explicit call to GC.Collect. Its a good practice to let the GC tune the frequency of its collections.
• # of Pinned Objects: This counter displays the number of pinned objects encountered in the last GC. This counter tracks the pinned objects only in the heaps that were garbage collected e.g. a Gen 0 GC would cause enumeration of pinned objects in the generation 0 heap only. A pinned object is one that the Garbage Collector cannot move in memory.
• # of Sink Blocks in use: This counter displays the current number of sync blocks in use. Sync blocks are per-object data structures allocated for storing synchronization information. Sync blocks hold weak references to managed objects and need to be scanned by the Garbage Collector. Sync blocks are not limited to storing synchronization information and can also store COM interop metadata. This counter was designed to indicate performance problems with heavy use of synchronization primitives.
• # Total committed Bytes: This counter displays the amount of virtual memory (in bytes) currently committed by the Garbage Collector. (Committed memory is the physical memory for which space has been reserved on the disk paging file).
• # Total reserved Bytes: This counter displays the amount of virtual memory (in bytes) currently reserved by the Garbage Collector. (Reserved memory is the virtual memory space reserved for the application but no disk or main memory pages have been used.)
• % Time in GC: % Time in GC is the percentage of elapsed time that was spent in performing a garbage collection (GC) since the last GC cycle. This counter is usually an indicator of the work done by the Garbage Collector on behalf of the application to collect and compact memory. This counter is updated only at the end of every GC and the counter value reflects the last observed value; its not an average.
• Allocated Bytes/sec: This counter displays the rate of bytes per second allocated on the GC Heap. This counter is updated at the end of every GC; not at each allocation. This counter is not an average over time; it displays the difference between the values observed in the last two samples divided by the duration of the sample interval.
• Finalization Survivors: This counter displays the number of garbage collected objects that survive a collection because they are waiting to be finalized. If these objects hold references to other objects then those objects also survive but are not counted by this counter; the "Promoted Finalization-Memory from Gen 0" and "Promoted Finalization-Memory from Gen 1" counters represent all the memory that survived due to finalization. This counter is not a cumulative counter; its updated at the end of every GC with count of the survivors during that particular GC only. This counter was designed to indicate the extra overhead that the application might incur because of finalization.
• Gen 0 Heap Size: This counter displays the maximum bytes that can be allocated in generation 0 (Gen 0): its does not indicate the current number of bytes allocated in Gen 0. A Gen 0 GC is triggered when the allocations since the last GC exceed this size. The Gen 0 size is tuned by the Garbage Collector and can change during the execution of the application. At the end of a Gen 0 collection the size of the Gen 0 heap is infact 0 bytes; this counter displays the size (in bytes) of allocations that would trigger the next Gen 0 GC. This counter is updated at the end of a GC; its not updated on every allocation.
• Gen 0 Promted Bytes/Sec: This counter displays the bytes per second that are promoted from generation 0 (youngest) to generation 1; objects that are promoted just because they are waiting to be finalized are not included in this counter. Memory is promoted when it survives a garbage collection. This counter was designed as an indicator of relatively long-lived objects being created per sec. This counter displays the difference between the values observed in the last two samples divided by the duration of the sample interval.
• Gen 1 heap size: This counter displays the current number of bytes in generation 1 (Gen 1); this counter does not display the maximum size of Gen 1. Objects are not directly allocated in this generation; they are promoted from previous Gen 0 GCs. This counter is updated at the end of a GC; its not updated on every allocation.
• Gen 1 Promted Bytes/Sec: This counter displays the bytes per second that are promoted from generation 1 to generation 2 (oldest); objects that are promoted just because they are waiting to be finalized are not included in this counter. Memory is promoted when it survives a garbage collection. Nothing is promoted from generation 2 since it is the oldest. This counter was designed as an indicator of very long-lived objects being created per sec. This counter displays the difference between the values observed in the last two samples divided by the duration of the sample interval.
• Gen 2 heap size: This counter displays the current number of bytes in generation 2 (Gen 2). Objects are not directly allocated in this generation; they are promoted from Gen 1 during previous Gen 1 GCs. This counter is updated at the end of a GC; its not updated on every allocation.
• Large Object Heap Size: This counter displays the current size of the Large Object Heap in bytes. Objects greater than 20 KBytes are treated as large objects by the Garbage Collector and are directly allocated in a special heap; they are not promoted through the generations. This counter is updated at the end of a GC; its not updated on every allocation.
• Process ID: This counter displays the process ID of the CLR process instance being monitored.
• Promted Finalization-Memory from Gen 0: This counter displays the bytes of memory that are promoted from generation 0 to generation 1 just because they are waiting to be finalized. This counter displays the value observed at the end of the last GC; its not a cumulative counter.
• Promted Memory from Gen 0: This counter displays the bytes of memory that survive garbage collection (GC) and are promoted from generation 0 to generation 1; objects that are promoted just because they are waiting to be finalized are not included in this counter. This counter displays the value observed at the end of the last GC; its not a cumulative counter.
• Promted Memory from Gen 1: This counter displays the bytes of memory that survive garbage collection (GC) and are promoted from generation 1 to generation 2; objects that are promoted just because they are waiting to be finalized are not included in this counter. This counter displays the value observed at the end of the last GC; its not a cumulative counter. This counter is reset to 0 if the last GC was a Gen 0 GC only.