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xen-devel
RE: [Xen-devel] planned csched improvements?
>>> "Tian, Kevin" <kevin.tian@xxxxxxxxx> 10.10.09 10:03 >>>
>>From: Jan Beulich
>>On a lightly loaded many-core non-hyperthreaded system (e.g. a single
>>CPU bound process in one VM, and only some background load elsewhere),
>>I see this CPU bound vCPU permanently switch between sockets, which is
>>a result of csched_cpu_pick() eagerly moving vCPU-s to "more idle"
>>sockets. It would seem that some minimal latency consideration might be
>>useful to get added here, so that a very brief interruption by another
>>vCPU doesn't result in unnecessary migration.
>
>there's a migration delay (default is 1ms) to judge cache hotness and
>thus avoid unnecessary migration. However so far it's only checked
>when one cpu wants to steal vcpus from other runqueue. Possibly it
>makes sense to add this check to csched_vcpu_acct, as a cold cache
>and cascade of other VCPU migrations could easily beat benefit on a
>"more idle" socket.
Where do you see this 1ms delay - I can't seem to spot it...
Jan
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