This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] [PATCH] Add migration_cost option to scheduler

Tian, Kevin wrote:
From: George Dunlap
Sent: Monday, March 09, 2009 8:56 PM

Hmm, I think this patch may not be exactly what we want.  It looks
like it checks for how long a vcpu has been in its current stat, not
how recently it has been running.  So if a vcpu sleeps for a long time
on a cpu that's running other workloads, then wakes up
(blocked->runnable), the cache is by no means "hot".  But since it has
only been in the "runnable" state for a few hundred cycles, it won't
be migrated, even though there's little cost.

Then to add a per-vcpu last_running_timestamp which is recorded when vcpu is scheduled out, could hit the purpose here?
Yes, it's more reasonable. I can make a patch.


However, if the pcpu was idle since the last time this vcpu ran (i.e.,
if we're just catching the vcpu in the process of waking up), the
cache *is* still hot.  Hmm....

If peer pcpu is idle, shouldn't it be skipped by load balancer running on
another pcpu, which is out of the cache-hot logic?


Xen-devel mailing list