[Xen-devel] [RFC] [PATCH] Accurate accounting for credit scheduler

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

The attached patch implements a first-cut of accurate TSC-based
accounting for the Credit scheduler.  Rather than debit a full 10ms of
credit on a scheduler tick (probabilistic), it debits credits
accurately based on time stamps.

The main problem this is meant to address is an attack on the
scheduler that allows a rogue guest to avoid ever being debited
credits.  The basic idea is that the rogue process checks time (using
rdtsc) periodically, and yields after 9.5ms.  Using this technique, a
guest can "steal" 95% of the cpu.  This is particularly an issue in
cloud environments.

Whenever we get a final version of this patch, it should be backported
to earlier versions as well.

Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

 -George

Attachment: accurate-credit.patch
Description: Text Data

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