Nir Soffer
2022-Mar-06 20:27 UTC
[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 ? ?): 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 ? ?): 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 at redhat.com>
---
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)
+ }
+
var offset uint64
for offset < size || queue.Len() > 0 {
for offset < size && inflightRequests() < *requests {
length := *requestSize
if size-offset < uint64(length) {
length = uint(size - offset)
}
startRead(offset, length)
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)
+ }
+
buf := make([]byte, *requestSize)
var offset uint64
for offset < size {
if size-offset < uint64(len(buf)) {
buf = buf[:offset-size]
}
err = h.Pread(buf, offset, nil)
if err != nil {
--
2.35.1
Richard W.M. Jones
2022-Mar-06 20:35 UTC
[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 ? ?): 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 ? ?): 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 at redhat.com> > --- > 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. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into KVM guests. http://libguestfs.org/virt-v2v