On 01/03/2011 10:47 AM, Avi Kivity wrote: > On 01/03/2011 06:35 PM, Eric Sandeen wrote: >> On 12/27/2010 03:41 AM, Avi Kivity wrote: >>> If Anaconda has just formatted a volume, we know that there is no data >>> on that volume that can be lost. We can therefore mount it, for the >>> duration of the installation, with barriers disabled (and make other >>> tradeoffs in the performance/integrity equation, like using >>> data=writeback for ext4). >>> >>> The installed image should enable barriers as usual. >>> >>> The result would be faster installation, and thus a better user experience. >> >> If we have just formatted it, this is probably ok; I assume that >> a power loss or crash during install would always result in a reinstall. > > Yes. No data can be lost. > >> Do you have any benchmarks of an install with/without barriers? > > No, but there are a lot of requests for kvm to run installs with > barriers disabled (on the host side, that is not issue fsync()s in > response to guest flushes) during installation. I consider my > suggestion better since it works for non-virtualized installs, and > removes the need for the management system to know when an install takes > place, and when it ends (on the other hand, it will only work for > installs of guests with the updated installer). > >> It'd be worth testing it on a rawhide compose (do we do that still?) >> because the whole barrier infrastructure has changed a lot upstream, >> recently. >> >> I'm a little less excited about other random tweaks for filesystems >> such as data=writeback, since this means the installer will be using >> codepaths that we don't recommend or support or test. >> >> But it'd be interesting to see some install perf numbers for a given >> kickstart file, I suppose, and for different install scenarios >> (ssd, sata, virt, etc). > > Sure. I imagine we'll see measurable benefit since installs are > metadata intensive. Yeah, it should be a win. Switching off barriers for a -freshly-made- filesystem is fine with me. Just need to be 100% sure that it doesn't persist in fstab, and that we do not mount -existing- filesystems with barriers off. -Eric _______________________________________________ Anaconda-devel-list mailing list Anaconda-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/anaconda-devel-list
