Page Comparison

The purpose of this page is to list tools and techniques that people can use to measure the performance of RAMCloud at various levels. The scope is intended to be broad, from using CPU performance counters, to RAMCloud's internal performance monitoring infrastructure, to existing RAMCloud client applications that collect statistics.

TimeTrace

If you are trying to analyze  the latency of a particular operation to see where the time is going, you will probably find the TimeTrace class useful.  An instance of this class keeps a circular buffer of events and the times when they occurred, which you can then print. Typically, you'll use the instance that is part of each RAMCloud context. You can then sprinkle calls to the record method in your code, like this:

context->timeTrace->record("starting read operation");
...
context->timeTrace->record("found hash table entry");
...

Then you run a benchmark that executes  the desired code  multiple times, enough to fill up the  circuit buffer.  Once the benchmark has run, you can print out the buffer to the log  using the printToLog method, like this:

context->printToLog();

If the recording is happening on a RAMCloud server but you are running a benchmark from a client machine, you can invoke the ServerControl RPC on the client to ask the server to dump its time trace buffer to the log:

cluster->objectServerControl(tableId, key, keyLength, WireFormat::LOG_TIME_TRACE);

In this example, cluster is a pointer to the RamCloud object for a cluster. TableId is the identifier for a table, and key and keyLength specify the key for an object; the RPC will be sent to the server containing the object given by these parameters, and the server will then dump its time trace log.

Internal RAMCloud Metrics

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