On Fri, Sep 18, 2020 at 11:22:15AM +0100, Richard W.M. Jones wrote: > On Fri, Sep 18, 2020 at 10:52:58AM +0100, Daniel P. Berrangé wrote: > > On Fri, Sep 18, 2020 at 10:44:03AM +0100, Richard W.M. Jones wrote: > > > So it didn't make any noticable difference in my test. I wonder if > > > the test guest I'm using (Fedora 32 using dracut) doesn't use parallel > > > compression? > > > > Do you do anything special to optimize storage ? If the thing using > > parallel CPUs in the guest is doing I/O you'd likely want to tune > > storage at same time. In current QEMU git master there's a change[1] > > that sets viort-blk/virtio-scsi num_queues to match SMP count, > > so the guest OS get fully parallel I/O from meach guest CPU. > > > > [1] a4eef0711b2cf7a7476c3e2c202a414b68a1baa0 > > I'm not using a new enough qemu to have that and it doesn't appear in > a released version, but I'll test again once we have a new enough > version.
You could set num_queues explicitly in v2v if desired, as the actual config knob has been around a while, only the default is changing in QEMU. > > > However I don't think it can cause a problem and it seems obvious that > > > it could benefit some cases. > > > > What's the default RAM size ? On hosts with very large numbers of CPUs > > (100's) you might need to scale up RAM size too so you keep a sane > > RAM-per-CPU ratio. Or default to host CPUs, but cap it at say 32. > > I'll cap the number of CPUs in this patch. > > Thanks, > > Rich. > > -- > Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones > Read my programming and virtualization blog: http://rwmj.wordpress.com > Fedora Windows cross-compiler. Compile Windows programs, test, and > build Windows installers. Over 100 libraries supported. > http://fedoraproject.org/wiki/MinGW Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| _______________________________________________ Libguestfs mailing list [email protected] https://www.redhat.com/mailman/listinfo/libguestfs
