Libguestfs - Jul 2017 - Re: read/write performance through mount point by guestmount

On Mon, Jul 31, 2017 at 09:49:00AM +0100, Richard W.M. Jones
wrote:
> On Mon, Jul 31, 2017 at 12:20:10PM +0800, lampahome wrote:
> > I mount the disk.qcow2 on the /home/test/, and create a 50GB file.
> 
> Mount the disk how?
OK, subject says using guestmount.

I'm surprised the slowdown isn't more than 95%.  It's using FUSE
which
goes through an insane number of layers, see the "Update" section in
this post:

  https://rwmj.wordpress.com/2009/10/30/fuse-support-for-libguestfs/

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org

if I mount through guestfs library in python or guestfish, the same
condition happenes?

I mean the insane number of layers and the performance

2017-07-31 16:52 GMT+08:00 Richard W.M. Jones <rjones@redhat.com>:
> On Mon, Jul 31, 2017 at 09:49:00AM +0100, Richard W.M. Jones wrote:
> > On Mon, Jul 31, 2017 at 12:20:10PM +0800, lampahome wrote:
> > > I mount the disk.qcow2 on the /home/test/, and create a 50GB
file.
> >
> > Mount the disk how?
>
> OK, subject says using guestmount.
>
> I'm surprised the slowdown isn't more than 95%.  It's using
FUSE which
> goes through an insane number of layers, see the "Update" section
in
> this post:
>
>   https://rwmj.wordpress.com/2009/10/30/fuse-support-for-libguestfs/
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~
> rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> libguestfs lets you edit virtual machines.  Supports shell scripting,
> bindings from many languages.  http://libguestfs.org
>

On Mon, Jul 31, 2017 at 06:52:28PM +0800, lampahome
wrote:
> if I mount through guestfs library in python or guestfish, the same
> condition happenes?
> 
> I mean the insane number of layers and the performance
No.  The layers are only present because guestmount uses FUSE.

libguestfs itself performs very well if you are careful to use it in
the correct way.

The architecture of libguestfs is described here:

  http://libguestfs.org/guestfs-internals.1.html#architecture

and we have tools for testing the performance of the virtio-serial
connection, qemu block layer and overhead of starting the appliance:

  https://github.com/libguestfs/libguestfs/tree/master/utils

and we have a page of tips on getting the best performance:

  http://libguestfs.org/guestfs-performance.1.html

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top