Re: [Qemu-devel] Modularizing QEMU RFC

[Fam Zheng <famz@redhat.com>]

On Mon, 08/03 11:01, Marc Marí wrote:
> Some profiling:
> 
> A QEMU with this configuration:
> ./configure --enable-sparse --enable-sdl --enable-gtk --enable-vte \
>  --enable-curses --enable-vnc --enable-vnc-{jpeg,tls,sasl,png,ws} \
>  --enable-virtfs --enable-brlapi --enable-curl --enable-fdt \
>  --enable-bluez --enable-kvm --enable-rdma --enable-uuid --enable-vde \
>  --enable-linux-aio --enable-cap-ng --enable-attr --enable-vhost-net \
>  --enable-vhost-scsi --enable-spice --enable-rbd --enable-libiscsi \
>  --enable-smartcard-nss --enable-guest-agent --enable-libusb \
>  --enable-usb-redir --enable-lzo --enable-snappy --enable-bzip2 \
>  --enable-seccomp --enable-coroutine-pool --enable-glusterfs \
>  --enable-tpm --enable-libssh2 --enable-vhdx --enable-quorum \
>  --enable-numa --enable-tcmalloc --target-list=x86_64-softmmu
> 
> Has dependencies on 142 libraries. It takes 60 ms between the run and
> the jump to the main function, and 80 ms between the run and the
> first kvm_entry.
> 
> A QEMU with the same configuration and --enable-modules has
> dependencies on 125 libraries. It takes 20 ms between the run and the
> jump to the main function, and 100 ms between the run and the first
> kvm_entry.

Which means 40 ms is saved because we reduced the size and dependency of QEMU
executable, but 60 ms is the extra cost of dynamical loading. That's a net
loss.

In your --enable-modules configuration, could you try comment out module_load
body and compare again, so we know how much time is spent in looking up and
loading modules?

Fam