Messages in this thread | | | From | Nikunj A Dadhania <> | Subject | Re: [RFC PATCH 0/4] Gang scheduling in CFS | Date | Mon, 26 Dec 2011 08:44:58 +0530 |
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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.
> Directed yield on PLE should provide intermediate results between doing > nothing and gang sched. > Yes, thats true, I have pasted the results from my first mail to highlight this:
+-------------+---------------------------+-------------------------+ | | V1 (%) | V2 (%) | + Benchmarks +-------------+-------------+-------------------------+ | | GangVsBase | GangVsPin | GangVsBase | GangVsPin | +-------------+-------------+-------------+-------------------------+ | ebizzy 2vm | 0 | 3 | 2 | 5 | | ebizzy 4vm | 1 | 0 | 4 | 3 | | ebizzy 8vm | 0 | 1 | 23 | 26 | +-------------+-------------+-------------+-------------------------+ > > btw you can get an additional speedup by enabling x2apic, for > default_send_IPI_mask_logical(). > In the host?
Nikunj
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