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[Xen-devel] Re: credit scheduler

To: David Xu <davidxu06@xxxxxxxxx>
Subject: [Xen-devel] Re: credit scheduler
From: George Dunlap <george.dunlap@xxxxxxxxxx>
Date: Tue, 21 Jun 2011 15:04:33 +0100
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On Fri, 2011-06-17 at 15:48 +0100, David Xu wrote:
> Hi,
> What's the meaning of runq_sort in csched_privates and runq_sort_last
> in csched_pcpu? Thanks.

The hint can be found in this comment (xen/common/sched_credit.c:1140):

    /* Inform each CPU that its runq needs to be sorted */

Every 30ms, the "master" cpu will increment prv->runq_sort.

Every 10ms, each individual cpu will check prv->runq_sort, to see if it
has been incremented (by comparing it to runq_sort_last).  If it has
incermented, then the cpu will sort its runqueue by priority.


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