On Wed, Oct 16, 2013 at 01:09:25PM -0600, Chris Murphy wrote: > Caching mode was none in all prior cases. Note that cache=none is almost never useful. It bypasses the host cache so you don't get the benefit of having lots of free host memory, plus causes endless pain because of filesystems that don't support O_DIRECT (eg. tmpfs) or have buggy O_DIRECT support (eg. glibc on top of older kernels). It took me quite a long time to realize this -- it was the default in libguestfs until quite recently :-( http://rwmj.wordpress.com/2013/09/02/new-in-libguestfs-allow-cache-mode-to-be-selected/#content > I made the suggested cache change for both LVM and qcow2; and > created the qcow2 file as suggested (adding lazy_refcount): > > Fedora 20 default standard partition guided install (ext4) to an LV takes 18m02s. Firstboot systemd-analyze: > Reboot, first boot systemd-analyze results: 852ms (kernel) + 1.425s (initrd) + 10.417s (userspace) = 12.695s > > The same install parameters to qcow2 on XFS takes 17m52s. Firstboot > systemd-analyze: > > 829ms (kernel) + 1.475s (initrd) + 11.693s (userspace) = 13.998s > > So that's a huge difference from the last attempt, and also > eliminates the gap between LVM and qcow2. Since I changed file > systems, I'm uncertain how much of a difference is due to unsafe > caching, or due to btrfs vs ext4. Just remember that cache=unsafe is called unsafe for a reason. If your host crashes, you can scramble the guest filesystems so it's impossible to recover. For testing you probably don't care ... Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
