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author | Daniel Martí <mvdan@mvdan.cc> | 2020-04-24 10:53:17 +0100 |
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committer | Daniel Martí <mvdan@mvdan.cc> | 2020-04-30 07:05:55 +0000 |
commit | b7e54d8d0784ceb21f7d4d406cf42c86a7fdb0f8 (patch) | |
tree | 863afbe8ccf550dcc25689193f6a0cbab9dbfea5 /lib | |
parent | e87b0644db46c2b313f420c657a4b308fb6bc2cb (diff) | |
download | go-b7e54d8d0784ceb21f7d4d406cf42c86a7fdb0f8.tar.gz go-b7e54d8d0784ceb21f7d4d406cf42c86a7fdb0f8.zip |
cmd/go: make 'mod verify' use multiple CPUs
'go mod verify' checksums one module zip at a time, which is
CPU-intensive on most modern machines with fast disks. As a result, one
can see a CPU bottleneck when running the command on, for example, a
module where 'go list -m all' lists ~440 modules:
$ /usr/bin/time go mod verify
all modules verified
11.47user 0.77system 0:09.41elapsed 130%CPU (0avgtext+0avgdata 24284maxresident)k
0inputs+0outputs (0major+4156minor)pagefaults 0swaps
Instead, verify up to GOMAXPROCS zips at once, which should line up
pretty well with the amount of processors we can use on a machine. The
results below are obtained via 'benchcmd -n 5 GoModVerify go mod verify'
on the same large module.
name old time/op new time/op delta
GoModVerify 9.35s ± 1% 3.03s ± 2% -67.60% (p=0.008 n=5+5)
name old user-time/op new user-time/op delta
GoModVerify 11.2s ± 1% 16.3s ± 3% +45.38% (p=0.008 n=5+5)
name old sys-time/op new sys-time/op delta
GoModVerify 841ms ± 9% 865ms ± 8% ~ (p=0.548 n=5+5)
name old peak-RSS-bytes new peak-RSS-bytes delta
GoModVerify 27.8MB ±13% 50.7MB ±27% +82.01% (p=0.008 n=5+5)
The peak memory usage nearly doubles, and there is some extra overhead,
but it seems clearly worth the tradeoff given that we see a ~3x speedup
on my laptop with 4 physical cores. The vast majority of developer
machines nowadays should have 2-4 cores at least.
No test or benchmark is included; one can benchmark 'go mod verify'
directly, as I did above. The existing tests also cover correctness,
including any data races via -race.
Fixes #38623.
Change-Id: I45d8154687a6f3a6a9fb0e2b13da4190f321246c
Reviewed-on: https://go-review.googlesource.com/c/go/+/229817
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Diffstat (limited to 'lib')
0 files changed, 0 insertions, 0 deletions