On 11/14/2011 01:54 AM, Tom Horsley wrote: > You might want to change the default virtio disk cache mode. > > I was just doing some tests (after finally getting the latest > virtio scsi drivers installed correctly on my Windows XP virtual > machine). > > The test was running the little "sdelete" tool which writes > a temp file full of zeroes to the disk in order to zero > out all the free space (very handy for converting the resulting > image to a maximally compressed qcow2 image). >
This is a bad test. Most likely the 'sdelete' utility insists on overwriting the file multiple times (but strangely doesn't flush the buffers); with cache=writeback these writes and overwrites hit the host RAM and return immediately. It's not the right workload to test performance. The recommendation is cache=none which gives good performance and cpu utilization. cache=writeback offers better performance, but it also interferes with other workloads on the same host by filling up page cache. It's okay to use it, but understand that it isn't free. -- error compiling committee.c: too many arguments to function _______________________________________________ virt mailing list [email protected] https://admin.fedoraproject.org/mailman/listinfo/virt
