[PATCH v2 19/25] netfs: Speed up buffered reading

[Eduard Zingerman]

On Mon, 2024-09-23 at 11:34 -0700, Manu Bretelle wrote:

[...]

> The qemu command invoked by vmtest is:
> 
> qemu-system-x86_64 "-nodefaults" "-display" "none" "-serial" "mon:stdio" \
>   "-enable-kvm" "-cpu" "host" "-qmp" "unix:/tmp/qmp-971717.sock,server=on,wait=off" \
>   "-chardev" "socket,path=/tmp/qga-888301.sock,server=on,wait=off,id=qga0" \
>   "-device" "virtio-serial" \
>   "-device" "virtserialport,chardev=qga0,name=org.qemu.guest_agent.0" \
>   "--device" "virtio-serial" \
>   "-chardev" "socket,path=/tmp/cmdout-508724.sock,server=on,wait=off,id=cmdout" \
>   "--device" "virtserialport,chardev=cmdout,name=org.qemu.virtio_serial.0" \
>   "-virtfs" "local,id=root,path=/,mount_tag=/dev/root,security_model=none,multidevs=remap" \
>   "-kernel" "/data/users/chantra/linux/arch/x86/boot/bzImage" \
>   "-no-reboot" "-append" "rootfstype=9p rootflags=trans=virtio,cache=mmap,msize=1048576 rw earlyprintk=serial,0,115200 printk.devkmsg=on console=0,115200 loglevel=7 raid=noautodetect init=/tmp/vmtest-init4PdCA.sh panic=-1" \
>   "-virtfs" "local,id=shared,path=/data/users/chantra/linux,mount_tag=vmtest-shared,security_model=none,multidevs=remap" \
>   "-smp" "2" "-m" "4G"

fwiw: removing "cache=mmap" from "rootflags" allows VM to boot and run tests.