qpprof

qpprof complements the pprof tool.

Commands

Use qpprof command --help to get more information.

Flat aggregation

Alternative flat aggregations allow you to get the top with some of the
nodes being folded to their callers.

For instance, take this copyBytes() function:

func copyBytes(b []byte) []byte {
  dst := make([]byte, len(b))
  copy(dst, b)
  return dst
}

If you benchmark it and use pprof top, then you’ll see this:

(pprof) top 5
37.56% runtime.mallocgc
12.16% runtime.memclrNoHeapPointers
 9.35% runtime.memmove
 8.47% runtime.scanobject
 6.42% runtime.scanblock

With flat-with-runtime you’ll get something that you would expect:

$ qpprof flat-with-runtime cpu.out
6.25s example.copyBytes
 40ms example.BenchmarkCopyBytes
 20ms testing.(*B).runN

There is also flat-with-stdlib that folds all standard library functions,
not just the runtime package.

Enriching the profile

Given a CPU profile X and executable E that was used to collect it, we can
generate a new CPU profile Y that contains even more useful information.

What we can add to the profile:

  • Explicit bound checks timings (displayed as runtime.boundcheck)
  • Explicit nil checks timings (displayed as runtime.nilcheck)

$ qpprof enrich -o=cpu2.out -exe=prog cpu.out
runtime.boundcheck: 7 samples (300ms)
runtime.nilcheck: 22 samples (300ms)

Now let’s open cpu2.out with pprof:

(pprof) top boundcheck|nilcheck
Active filters:
   focus=boundcheck|nilcheck
Showing nodes accounting for 0.60s, 1.10% of 54.68s total
Showing top 10 nodes out of 132
      flat  flat%   sum%        cum   cum%
     0.30s  0.55%  0.55%      0.30s  0.55%  runtime.boundcheck (inline)
     0.30s  0.55%  1.10%      0.30s  0.55%  runtime.nilcheck (inline)

The implicit bound checks are now explicit, visible in the profile.

GitHub

View Github