Re: [Xen-users] Massive performance regression

[Phil Susi <psusi@xxxxxxxxxx>]

On 2/28/2018 11:52 AM, Phil Susi wrote:
> On 2/28/2018 11:14 AM, Phil Susi wrote:
>> My server is running Ubuntu 16.04 using Xen 4.6.5-0ubuntu1.4.  There
>> must have been an update in the last few weeks that seems to have caused
>> a terrible performance regression.  When I try to fire up a testing vm
>> to test a live cd, it takes several minutes before anything shows up on
>> the display, and during that time, qemu-system-i386 is burning through
>> 100% of a cpu ( out of 8 ).

I found it.  I first tried reverting to an older Dom0 kernel without the
spectre patches to no avail.  Then I noticed that qemu had been patched
for it as well.  After reverting qemu, boot time for a livecd in a domU
went from 4.5 minutes ( where you never even see the LILO menu at all
and the guest kernel keeps reporting cpu soft lockups ) to less than 30
seconds.

Whatever they did to qemu fscked it up.


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