On Fri, Nov 03, 2017 at 09:10:45AM +0000, Dr. David Alan Gilbert wrote: > * Paul Schlacter ([email protected]) wrote: > > latest progress： > > use centos 7.2 https://cloud.centos.org/centos/7/images/ > > test version: 1511 1601 1604 1606 1608 > > > > From the above version in turn test, found the previous version 1511 1601 > > 1603 have the problem, > > The latter two versions 1606 1608 are normal, dont't have the prblem, > > Normal is cache = writeback io significantly higher than none mode > > > > why? > > It's a fun bug, but I don't know the cause - the fact it's dependent > on guest version but fixed, suggests something changed in the guest > kernel. If you really wanted to figure out why I guess the only way > would be to walk through the CentOS guest kernel versions and find the > exact kernel that fixed it; then we could hunt down which change fixed > it. > > (I've cc'd in Stefan for block stuff, but this is sounding more guest > than qemu)
Please provide full details of the problem you are observing: 1. qemu command-line on the host (ps aux | grep qemu) 2. dd command-line inside the guest 3. "Good" output and "bad" output Stefan
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