Messages in this thread |  | | | From | Nikunj A Dadhania <> | | Subject | Re: [RFC PATCH 0/4] Gang scheduling in CFS | | Date | Tue, 27 Dec 2011 15:14:20 +0530 |
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On Tue, 27 Dec 2011 11:17:29 +0200, Avi Kivity <avi@redhat.com> wrote: > On 12/27/2011 05:15 AM, Nikunj A Dadhania wrote: > > On Mon, 26 Dec 2011 08:44:58 +0530, Nikunj A Dadhania <nikunj@linux.vnet.ibm.com> wrote: > > > On Sun, 25 Dec 2011 12:58:15 +0200, Avi Kivity <avi@redhat.com> wrote: > > > > On 12/23/2011 12:36 PM, Ingo Molnar wrote: > > > > > * Nikunj A Dadhania <nikunj@linux.vnet.ibm.com> wrote: > > > > > > > > [...] > > > > > > > > > > > > I see the main difference between both the reports is: > > > > > > native_flush_tlb_others. > > > > > > > > > > So it would be important to figure out why ebizzy gets into so > > > > > many TLB flushes and why gang scheduling makes it go away. > > > > > > > > The second part is easy - a remote tlb flush involves IPIs to many other > > > > vcpus (possible waking them up and scheduling them), then busy-waiting > > > > until they acknowledge the flush. Gang scheduling is really good here > > > > since it shortens the busy wait, would be even better if we schedule > > > > halted vcpus (see the yield_on_hlt module parameter, set to 0). > > > I will check this. > > > > > I am seeing a drop of ~44% when setting yield_on_hlt = 0 > > > > A drop of 44% of what? > records/sec
Ebizzy - 2VM running in parallel, both having gang scheduling enabled.
yield_on_hlt=1 yield_on_hlt=0 EbzyRecords/sec 41955.50 23285.00 -44
Nikunj
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