This should be changed also on the client side.
The libnbd part is here:
https://gitlab.com/nbdkit/libnbd/-/merge_requests/21
We may want to change also the nbd client code used in qemu-img. I can look at
this later.
> On 18 Apr 2025, at 17:24, Nir Soffer <nir...@gmail.com> wrote:
>
> Testing with qemu-nbd shows that computing a hash of an image via
> qemu-nbd is 5-7 times faster with this change.
>
> Tested with 2 qemu-nbd processes:
>
> $ ./qemu-nbd-after -r -t -e 0 -f raw -k /tmp/after.sock
> /var/tmp/bench/data-10g.img &
> $ ./qemu-nbd-before -r -t -e 0 -f raw -k /tmp/before.sock
> /var/tmp/bench/data-10g.img &
>
> With nbdcopy, using 4 NBD connections:
>
> $ hyperfine -w 3 "./nbdcopy --blkhash
> 'nbd+unix:///?socket=/tmp/before.sock' null:"
> "./nbdcopy --blkhash
> 'nbd+unix:///?socket=/tmp/after.sock' null:"
> Benchmark 1: ./nbdcopy --blkhash 'nbd+unix:///?socket=/tmp/before.sock'
> null:
> Time (mean ± σ): 8.670 s ± 0.025 s [User: 5.670 s, System:
> 7.113 s]
> Range (min … max): 8.620 s … 8.703 s 10 runs
>
> Benchmark 2: ./nbdcopy --blkhash 'nbd+unix:///?socket=/tmp/after.sock'
> null:
> Time (mean ± σ): 1.839 s ± 0.008 s [User: 4.651 s, System:
> 1.882 s]
> Range (min … max): 1.830 s … 1.853 s 10 runs
>
> Summary
> ./nbdcopy --blkhash 'nbd+unix:///?socket=/tmp/after.sock' null: ran
> 4.72 ± 0.02 times faster than ./nbdcopy --blkhash
> 'nbd+unix:///?socket=/tmp/before.sock' null:
>
> With blksum, using one NBD connection:
>
> $ hyperfine -w 3 "blksum 'nbd+unix:///?socket=/tmp/before.sock'" \
> "blksum 'nbd+unix:///?socket=/tmp/after.sock'"
> Benchmark 1: blksum 'nbd+unix:///?socket=/tmp/before.sock'
> Time (mean ± σ): 13.606 s ± 0.081 s [User: 5.799 s, System:
> 6.231 s]
> Range (min … max): 13.516 s … 13.785 s 10 runs
>
> Benchmark 2: blksum 'nbd+unix:///?socket=/tmp/after.sock'
> Time (mean ± σ): 1.946 s ± 0.017 s [User: 4.541 s, System:
> 1.481 s]
> Range (min … max): 1.912 s … 1.979 s 10 runs
>
> Summary
> blksum 'nbd+unix:///?socket=/tmp/after.sock' ran
> 6.99 ± 0.07 times faster than blksum
> 'nbd+unix:///?socket=/tmp/before.sock'
>
> This will improve other usage of unix domain sockets on macOS, I tested
> only qemu-nbd.
>
> Signed-off-by: Nir Soffer <nir...@gmail.com>
> ---
> io/channel-socket.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/io/channel-socket.c b/io/channel-socket.c
> index 608bcf066e..b858659764 100644
> --- a/io/channel-socket.c
> +++ b/io/channel-socket.c
> @@ -410,6 +410,19 @@ qio_channel_socket_accept(QIOChannelSocket *ioc,
> }
> #endif /* WIN32 */
>
> +#if __APPLE__
> + /* On macOS we need to tune unix domain socket buffer for best
> performance.
> + * Apple recommends sizing the receive buffer at 4 times the size of the
> + * send buffer.
> + */
> + if (cioc->localAddr.ss_family == AF_UNIX) {
> + const int sndbuf_size = 1024 * 1024;
> + const int rcvbuf_size = 4 * sndbuf_size;
> + setsockopt(cioc->fd, SOL_SOCKET, SO_SNDBUF, &sndbuf_size,
> sizeof(sndbuf_size));
> + setsockopt(cioc->fd, SOL_SOCKET, SO_RCVBUF, &rcvbuf_size,
> sizeof(rcvbuf_size));
> + }
> +#endif /* __APPLE__ */
> +
> qio_channel_set_feature(QIO_CHANNEL(cioc),
> QIO_CHANNEL_FEATURE_READ_MSG_PEEK);
>
> --
> 2.39.5 (Apple Git-154)
>
