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

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) + } +

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) + } +