Re: [Libguestfs] [PATCH libnbd 1/3] golang: examples: Do not initialize pread buffer

On Sun, Mar 06, 2022 at 10:27:28PM +0200, Nir Soffer wrote: > The aio_copy example checks errors properly, so it will not leak > uninitialized memory to the destination image. Testing shows 5% speedup > when copying a real image. > > $ qemu-nbd --read-only --persistent --shared 8 --cache none --aio native \ > --socket /tmp/src.sock --format raw fedora-35-data.raw & > > $ hyperfine -p "sleep 5" "./aio_copy-init $SRC >/dev/null" "./aio_copy-no-init $SRC >/dev/null" > > Benchmark 1: ./aio_copy-init nbd+unix:///?socket=/tmp/src.sock >/dev/null > Time (mean ± σ): 1.452 s ± 0.027 s [User: 0.330 s, System: 0.489 s] > Range (min … max): 1.426 s … 1.506 s 10 runs > > Benchmark 2: ./aio_copy-no-init nbd+unix:///?socket=/tmp/src.sock >/dev/null > Time (mean ± σ): 1.378 s ± 0.009 s [User: 0.202 s, System: 0.484 s] > Range (min … max): 1.369 s … 1.399 s 10 runs > > Summary > './aio_copy-no-init nbd+unix:///?socket=/tmp/src.sock >/dev/null' ran > 1.05 ± 0.02 times faster than './aio_copy-init nbd+unix:///?socket=/tmp/src.sock >/dev/null' > > Signed-off-by: Nir Soffer <nsoffer(a)redhat.com&gt; > --- > golang/examples/aio_copy/aio_copy.go | 5 +++++ > golang/examples/simple_copy/simple_copy.go | 5 +++++ > 2 files changed, 10 insertions(+) > > diff --git a/golang/examples/aio_copy/aio_copy.go b/golang/examples/aio_copy/aio_copy.go > index bb20b478..89eac4df 100644 > --- a/golang/examples/aio_copy/aio_copy.go > +++ b/golang/examples/aio_copy/aio_copy.go > @@ -84,20 +84,25 @@ func main() { > err = h.ConnectUri(flag.Arg(0)) > if err != nil { > panic(err) > } > > size, err := h.GetSize() > if err != nil { > panic(err) > } > > + err = h.SetPreadInitialize(false) > + if err != nil { > + panic(err) > + } > + In patch #2 you added a comment above the call. Because this is an example and so people may just copy the code blindly without understanding it, I think adding a comment here and below is worth doing too. > diff --git a/golang/examples/simple_copy/simple_copy.go b/golang/examples/simple_copy/simple_copy.go > index e8fa1f76..2a2ed0ff 100644 > --- a/golang/examples/simple_copy/simple_copy.go > +++ b/golang/examples/simple_copy/simple_copy.go > @@ -63,20 +63,25 @@ func main() { > err = h.ConnectUri(flag.Arg(0)) > if err != nil { > panic(err) > } > > size, err := h.GetSize() > if err != nil { > panic(err) > } > > + err = h.SetPreadInitialize(false) > + if err != nil { > + panic(err) > + } > + And above this one.