pprof

README

http/pprof Profiling

Using the http/pprof support you can profile your web applications and services to see exactly where your performance or memory is being taken.

Building and Running the Project

Build and run the example program.

    go build
    ./pprof

Test it is working.

    http://localhost:4000/sendjson

To add load to the service while running profiling we can run these command.

Send 1M request using 8 connections.

    hey -m POST -c 8 -n 1000000 "http://localhost:4000/sendjson"

Raw http/pprof

We already added the following import so we can include the profiling route to our web service.

    import _ "net/http/pprof"

Look at the basic profiling stats from the new endpoint.

    http://localhost:4000/debug/pprof

Run a single search from the Browser and then refresh the profile information.

    http://localhost:4000/sendjson

Put some load of the web application. Review the raw profiling information once again.

    hey -m POST -c 8 -n 1000000 "http://localhost:4000/sendjson"

Interactive Profiling

Heap Profiling

Run the pprof tool.

    go tool pprof -<option> ./pprof http://localhost:4000/debug/pprof/heap

Options help to see pressure on heap over time:

    -alloc_space:       All allocations happened since program start (default).
    -alloc_objects:     Number of object allocated at the time of profile.

Options help to see the current status of the heap:

    -inuse_space:       Allocations live at the time of profile.
    -inuse_objects:     Number of bytes allocated at the time of profile.

If you want to reduce memory consumption, look at the -inuse_space profile collected during normal program operation.

If you want to improve execution speed, look at the -alloc_objects profile collected after significant running time or at program end.

CPU Profiling

Run the Go pprof tool in another window or tab to review cpu information.

    go tool pprof http://localhost:4000/debug/pprof/profile

If you include the binary when using the browser tooling, you can get information down to the assembly.

    go tool pprof -http :3000 ./pprof http://localhost:4000/debug/pprof/profile

Note that goroutines in syscall state consume an OS thread, other goroutines do not(except for goroutines that called runtime.LockOSThread, which is, unfortunately, not visible in the profile).

Note that goroutines in IO wait state do NOT consume an OS thread. They are parked on the non-blocking network poller.

Comparing Profiles

Take a snapshot of the current heap profile. Then do the same for the cpu profile.

    curl -s http://localhost:4000/debug/pprof/heap > base.heap

After some time, take another snapshot:

    curl -s http://localhost:4000/debug/pprof/heap > current.heap

Now compare both snapshots against the binary and get into the pprof tool:

    go tool pprof -inuse_space -base base.heap current.heap