Documentation
¶
Overview ¶
package dump is a utility for printing memory allocations info using printf. This allows instrumentation of code for memory allocation analysis with very little effort.
- MemStats: Uses `runtime.ReadMemStats`. The numbers shown include "garbage" not yet collected by GC according to Go docs.
- MemProf: Uses code from pprof package to show stats as would be shown by pprof tool. The pprof itself uses some probabilistic approach. Hopefully this is more accurate than `MemStats` and do not include "garbage".
- WriteHeapDump(): Write pprof heap profiles at any point in code.
Sample usage:
func Example() []int64 {
// Write pprof heap profile at the start and end of function
dump.WriteHeapDump(fmt.Sprintf("heap-example-before"))
defer dump.WriteHeapDump(fmt.Sprintf("heap-example-after"))
// Take a snapshot at the start of a function
// Capture and print deltas at the end
memProf := dump.NewMemProf("example")
defer memProf.PrintDiff()
// Similar for memStats
memStats := dump.NewMemStats("example")
defer memStats.PrintDiff()
// allocate memory
allocateMem := func () []int64 {
return make([]int64, 100000)
}
var result []int64
for i := 0; i < 1000; i++{
result = append(result, allocateMem()...)
}
return result
}
This will produce results similar to this:
WRITTEN HEAP DUMP TO /Users/philip/thanos/github.com/ppanyukov/go-dump/heap-example-before.pb.gz MEM STATS DIFF: example example - AFTER -> Delta HeapAlloc : 219.76K 963.52M -> 963.30M HeapObjects: 203 408 -> 205 MEM PROF DIFF: example example - AFTER -> Delta InUseBytes : 0 816.39M -> 816.39M InUseObjects: 0 1 -> 1 AllocBytes : 1.26M 4.69G -> 4.69G AllocObjects: 6 808 -> 802 WRITTEN HEAP DUMP TO /Users/philip/thanos/github.com/ppanyukov/go-dump/heap-example-after.pb.gz
The size of 1,000,000 int64 values is `800MB`, and can be seen `MemProf` reports this quite close to this number. The MemStats are slightly off with its `963.30M` as this number includes objects not yet collected by GC.
To use pprof tool to see allocations use this command:
go tool pprof \ -sample_index=inuse_space \ -edgefraction=0 \ -functions \ -http=:8081 \ -base /Users/philip/thanos/github.com/ppanyukov/go-dump/heap-example-before.pb.gz \ /Users/philip/thanos/github.com/ppanyukov/go-dump/heap-example-after.pb.gz
This would report figures like so:
Showing nodes accounting for 778.57MB, 100% of 778.57MB total
Also close to `800MB`.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func WriteHeapDump ¶
func WriteHeapDump(name string)
WriteHeapDump is a convenience method to write a pprof heap dump which can be examined with pprof tool. The file `{name}.pb.gz` is written to `heapDumpDir`.
Call at the start and end of the function to see how much and where things were allocated within that function.
Types ¶
type MemProf ¶
type MemProf struct {
Name string
AllocObjects int64
AllocBytes int64
InUseObjects int64
InUseBytes int64
}
MemProf is memory heap profile as would be shown by pprof tool.
func NewMemProf ¶
NewMemProf creates memory heap profile as would be shown by pprof tool. Code here is based largely on pprof package with some copy/paste.
Source Files
Directories