Unlike alloc_space, inuse_space tracks heap memory that is live and not yet collected by garbage collection. In this perspective, there is not much significant difference between preallocated and growing versions. inuse_space is generally used for checking memory leaks.
go test -run '^$' \
-bench '^BenchmarkBuildMessageBatch$/^implementation=growing$' \
-benchtime=100x \
-memprofilerate=1 \
-memprofile=/tmp/codec01-message-batch-growing-memory.pprof
goos: linux
goarch: arm64
pkg: codec01
BenchmarkBuildMessageBatch/implementation=growing-12 100 86302 ns/op 741.58 MB/s 285437 B/op 19 allocs/op
PASS
ok codec01 0.024s
go test -run '^$' \
-bench '^BenchmarkBuildMessageBatch$/^implementation=preallocated$' \
-benchtime=100x \
-memprofilerate=1 \
-memprofile=/tmp/codec01-message-batch-preallocated-memory.pprof
goos: linux
goarch: arm64
pkg: codec01
BenchmarkBuildMessageBatch/implementation=preallocated-12 100 27129 ns/op 2359.10 MB/s 65537 B/op 1 allocs/op
PASS
ok codec01 0.016sgo tool pprof -top -inuse_space \
/tmp/codec01-message-batch-growing-memory.pprof
File: codec01.test
Build ID: f4a53b5a12db4d35158b288d82f85a5798e33258
Type: inuse_space
Time: 2026-11-01 20:40:44 PST
Showing nodes accounting for 115.37kB, 99.06% of 116.46kB total
Dropped 64 nodes (cum <= 0.58kB)
flat flat% sum% cum cum%
72.22kB 62.01% 62.01% 72.22kB 62.01% codec01.BuildMessageBatchGrowing (inline)
36.19kB 31.07% 93.08% 36.19kB 31.07% runtime.mallocgc
3.52kB 3.02% 96.10% 3.52kB 3.02% sync.(*Pool).pinSlow
1.80kB 1.54% 97.65% 1.80kB 1.54% regexp.onePassCopy
1.38kB 1.18% 98.83% 1.38kB 1.18% regexp/syntax.(*compiler).inst (inline)
0.18kB 0.15% 98.98% 3.59kB 3.08% regexp.compile
0.09kB 0.08% 99.06% 1.86kB 1.60% regexp.newOnePassMachine (inline)
0 0% 99.06% 7.52kB 6.46% codec01.BenchmarkBuildMessageBatch
0 0% 99.06% 72.33kB 62.11% codec01.BenchmarkBuildMessageBatch.func1
0 0% 99.06% 1.95kB 1.68% fmt.Fprintf
0 0% 99.06% 1.95kB 1.68% fmt.newPrinter
0 0% 99.06% 1.86kB 1.60% regexp.(*Regexp).MatchString (inline)
0 0% 99.06% 1.86kB 1.60% regexp.(*Regexp).doExecute
0 0% 99.06% 1.86kB 1.60% regexp.(*Regexp).doMatch (inline)
0 0% 99.06% 1.86kB 1.60% regexp.(*Regexp).doOnePass
0 0% 99.06% 3.59kB 3.08% regexp.Compile (inline)
0 0% 99.06% 1.81kB 1.56% regexp.compileOnePass
0 0% 99.06% 1.38kB 1.18% regexp/syntax.(*compiler).compile
0 0% 99.06% 1.38kB 1.18% regexp/syntax.(*compiler).rune
0 0% 99.06% 1.42kB 1.22% regexp/syntax.Compile
0 0% 99.06% 22.78kB 19.56% runtime.allocm
0 0% 99.06% 6.55kB 5.62% runtime.gcBgMarkWorker
0 0% 99.06% 5.20kB 4.46% runtime.gcStart.func4
0 0% 99.06% 9kB 7.73% runtime.mProfStackInit (inline)
0 0% 99.06% 9kB 7.73% runtime.makeProfStackFP (inline)
0 0% 99.06% 9kB 7.73% runtime.makeslice
0 0% 99.06% 10.31kB 8.85% runtime.malg
0 0% 99.06% 10.39kB 8.92% runtime.mcall
0 0% 99.06% 10.91kB 9.36% runtime.mcommoninit
0 0% 99.06% 1.88kB 1.61% runtime.mpreinit (inline)
0 0% 99.06% 7.20kB 6.18% runtime.mstart
0 0% 99.06% 7.20kB 6.18% runtime.mstart0
0 0% 99.06% 7.20kB 6.18% runtime.mstart1
0 0% 99.06% 22.78kB 19.56% runtime.newm
0 0% 99.06% 26.89kB 23.09% runtime.newobject
0 0% 99.06% 6.81kB 5.85% runtime.newproc.func1
0 0% 99.06% 6.81kB 5.85% runtime.newproc1
0 0% 99.06% 10.39kB 8.92% runtime.park_m
0 0% 99.06% 12.39kB 10.64% runtime.resetspinning
0 0% 99.06% 17.59kB 15.10% runtime.schedule
0 0% 99.06% 5.20kB 4.46% runtime.startTheWorldWithSema
0 0% 99.06% 17.59kB 15.10% runtime.startm
0 0% 99.06% 12.01kB 10.31% runtime.systemstack
0 0% 99.06% 17.59kB 15.10% runtime.wakep
0 0% 99.06% 2.05kB 1.76% sync.(*Once).Do (inline)
0 0% 99.06% 2.05kB 1.76% sync.(*Once).doSlow
0 0% 99.06% 3.72kB 3.19% sync.(*Pool).Get
0 0% 99.06% 3.52kB 3.02% sync.(*Pool).pin
0 0% 99.06% 7.52kB 6.46% testing.(*B).Run
0 0% 99.06% 2.08kB 1.78% testing.(*B).run
0 0% 99.06% 1.95kB 1.68% testing.(*B).run.func1
0 0% 99.06% 79.85kB 68.57% testing.(*B).run1.func1
0 0% 99.06% 79.85kB 68.57% testing.(*B).runN
0 0% 99.06% 5.45kB 4.68% testing.(*matcher).fullName
0 0% 99.06% 5.45kB 4.68% testing.simpleMatch.matches
0 0% 99.06% 5.45kB 4.68% testing/internal/testdeps.TestDeps.MatchString
go tool pprof -top -inuse_space \
/tmp/codec01-message-batch-preallocated-memory.pprof
File: codec01.test
Build ID: f4a53b5a12db4d35158b288d82f85a5798e33258
Type: inuse_space
Time: 2026-11-01 20:40:48 PST
Showing nodes accounting for 100kB, 98.79% of 101.23kB total
Dropped 59 nodes (cum <= 0.51kB)
flat flat% sum% cum cum%
64kB 63.22% 63.22% 64kB 63.22% codec01.BuildMessageBatchPreallocated (inline)
30.63kB 30.26% 93.49% 30.63kB 30.26% runtime.mallocgc
2.05kB 2.02% 95.51% 2.05kB 2.02% regexp.onePassCopy
1.76kB 1.74% 97.24% 1.76kB 1.74% sync.(*Pool).pinSlow
1.38kB 1.36% 98.60% 1.38kB 1.36% regexp/syntax.(*compiler).inst (inline)
0.19kB 0.19% 98.79% 3.84kB 3.80% regexp.compile
0 0% 98.79% 6.05kB 5.98% codec01.BenchmarkBuildMessageBatch
0 0% 98.79% 64kB 63.22% codec01.BenchmarkBuildMessageBatch.func2
0 0% 98.79% 2.10kB 2.08% fmt.Fprintf
0 0% 98.79% 1.96kB 1.94% fmt.newPrinter
0 0% 98.79% 0.54kB 0.53% main.main
0 0% 98.79% 3.84kB 3.80% regexp.Compile (inline)
0 0% 98.79% 2.06kB 2.04% regexp.compileOnePass
0 0% 98.79% 1.38kB 1.36% regexp/syntax.(*compiler).compile
0 0% 98.79% 1.38kB 1.36% regexp/syntax.(*compiler).rune
0 0% 98.79% 1.42kB 1.40% regexp/syntax.Compile
0 0% 98.79% 17.59kB 17.37% runtime.allocm
0 0% 98.79% 6.22kB 6.14% runtime.gcBgMarkWorker
0 0% 98.79% 5.20kB 5.13% runtime.gcStart.func4
0 0% 98.79% 6.75kB 6.67% runtime.mProfStackInit (inline)
0 0% 98.79% 0.54kB 0.53% runtime.main
0 0% 98.79% 6.75kB 6.67% runtime.makeProfStackFP (inline)
0 0% 98.79% 6.75kB 6.67% runtime.makeslice
0 0% 98.79% 9.38kB 9.26% runtime.malg
0 0% 98.79% 5.20kB 5.13% runtime.mcall
0 0% 98.79% 8.18kB 8.08% runtime.mcommoninit
0 0% 98.79% 1.41kB 1.39% runtime.mpreinit (inline)
0 0% 98.79% 7.20kB 7.11% runtime.mstart
0 0% 98.79% 7.20kB 7.11% runtime.mstart0
0 0% 98.79% 7.20kB 7.11% runtime.mstart1
0 0% 98.79% 17.59kB 17.37% runtime.newm
0 0% 98.79% 23.62kB 23.33% runtime.newobject
0 0% 98.79% 6.81kB 6.73% runtime.newproc.func1
0 0% 98.79% 6.81kB 6.73% runtime.newproc1
0 0% 98.79% 5.20kB 5.13% runtime.park_m
0 0% 98.79% 7.20kB 7.11% runtime.resetspinning
0 0% 98.79% 12.39kB 12.24% runtime.schedule
0 0% 98.79% 5.20kB 5.13% runtime.startTheWorldWithSema
0 0% 98.79% 12.39kB 12.24% runtime.startm
0 0% 98.79% 12.01kB 11.86% runtime.systemstack
0 0% 98.79% 12.39kB 12.24% runtime.wakep
0 0% 98.79% 2.06kB 2.04% sync.(*Once).Do (inline)
0 0% 98.79% 2.06kB 2.04% sync.(*Once).doSlow
0 0% 98.79% 1.96kB 1.94% sync.(*Pool).Get
0 0% 98.79% 1.76kB 1.74% sync.(*Pool).pin
0 0% 98.79% 6.16kB 6.09% testing.(*B).Run
0 0% 98.79% 2.10kB 2.08% testing.(*B).run
0 0% 98.79% 1.96kB 1.94% testing.(*B).run.func1
0 0% 98.79% 70.05kB 69.21% testing.(*B).run1.func1
0 0% 98.79% 70.16kB 69.31% testing.(*B).runN
0 0% 98.79% 0.54kB 0.53% testing.(*M).Run
0 0% 98.79% 3.84kB 3.80% testing.(*matcher).fullName
0 0% 98.79% 3.84kB 3.80% testing.simpleMatch.matches
0 0% 98.79% 3.84kB 3.80% testing/internal/testdeps.TestDeps.MatchString