code review 156340043: driver: fix latency collection

driver: fix latency collection
This change:
http://build.golang.org/perfdetail?commit=28de6f41b1c77c5cb9046056fb29b96b9583a3a5&commit0=90a7c3c86944759bd88007c09f7a311c42f4bef8&builder=linux-amd64-perf&benchmark=http
shows +25% heap size increase on linux/http-8.
I've looked at the logs and the reason is that during benchmarking of the old commit
all runs used 500000 iterations:

2014/10/17 21:32:15 Benchmarking 500000 iterations
gc1058(8): 31+57+758+24 us, 8 -> 16 MB, 143644 (126950432-126806788) objects, 136 goroutines, 1586/0/657 sweeps, 202(6287) handoff, 26(217) steal, 438/13/0 yields

And during benchmarking of the new commit one of the runs used 1000000 iterations:

2014/10/17 21:38:51 Benchmarking 1000000 iterations
gc540(8): 29+33+1082+13 us, 12 -> 24 MB, 194738 (63964975-63770237) objects, 136 goroutines, 2019/0/658 sweeps, 227(5856) handoff, 35(251) steal, 656/107/7 yields

This resulted in twice larger latency array. Which is 4MB.
Multiplied by GOGC gives exactly the additional 8MB reported.

Simply create maximum latency array always.

[dvyukov, 2014-10-18 14:07:52]

Hello adg@golang.org, bradfitz@golang.org (cc:
golang-codereviews@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go.benchmarks

[adg1, 2014-10-20 00:20:57]

LGTM

[dvyukov, 2014-10-20 06:24:12]

*** Submitted as
https://code.google.com/p/go/source/detail?r=82cb5aac589f&repo=benchmarks ***

driver: fix latency collection
This change:
http://build.golang.org/perfdetail?commit=28de6f41b1c77c5cb9046056fb29b96b958...
shows +25% heap size increase on linux/http-8.
I've looked at the logs and the reason is that during benchmarking of the old
commit
all runs used 500000 iterations:

2014/10/17 21:32:15 Benchmarking 500000 iterations
gc1058(8): 31+57+758+24 us, 8 -> 16 MB, 143644 (126950432-126806788) objects,
136 goroutines, 1586/0/657 sweeps, 202(6287) handoff, 26(217) steal, 438/13/0
yields

And during benchmarking of the new commit one of the runs used 1000000
iterations:

2014/10/17 21:38:51 Benchmarking 1000000 iterations
gc540(8): 29+33+1082+13 us, 12 -> 24 MB, 194738 (63964975-63770237) objects, 136
goroutines, 2019/0/658 sweeps, 227(5856) handoff, 35(251) steal, 656/107/7
yields

This resulted in twice larger latency array. Which is 4MB.
Multiplied by GOGC gives exactly the additional 8MB reported.

Simply create maximum latency array always.

LGTM=adg
R=adg, bradfitz
CC=golang-codereviews
https://codereview.appspot.com/156340043