Intel® VTune™ Amplifier XE and Intel® VTune™ Amplifier for Systems Help
While Concurrency analysis helps identify where your application is not parallel, Locks and Waits analysis helps identify the cause of ineffective processor utilization. One of the most common problems is threads waiting too long on synchronization objects (locks). Performance suffers when waits occur while cores are under-utilized.
Locks and Waits analysis uses user-mode sampling and tracing collection. With this analysis you can estimate the impact each synchronization object has on the application and understand how long the application had to wait on each synchronization object, or in blocking APIs, such as sleep and blocking I/O.
There are two groups of synchronization objects supported by the Intel® VTune™ Amplifier:
objects usually used for synchronization between threads, such as Mutex or Semaphore
objects associated with waits on I/O operations, such as Stream
Syntax:
$ amplxe-cl -collect locksandwaits [-knob <knobName=knobValue>] [--] <target>
Knobs: sampling-interval, enable-user-tasks, enable-user-sync
For the most current information on available knobs (configuration options) for the Locks and Waits analysis, enter:
$ amplxe-cl -help collect locksandwaits
Example:
This example shows how to run the Locks and Waits analysis on myApplication with the enabled User synchronization API profiling:
$ amplxe-cl -collect locksandwaits -knob enable-user-sync=true -- home/test/myApplicationWhen the data collection is complete, do one of the following to view the result:
Use the -report action to view the data from command line.
Use the -report-output action to write report to a .txt or .csv file
Open the data collection result (*.amplxe) in the VTune Amplifier graphical interface.