[Xen-devel] Linux spin lock enhancement on xen

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

Hi guys,

Check out the attached patches. I changed the spin lock semantics so the
lock contains the vcpu id of the vcpu holding it. This then tells xen
to make that vcpu runnable if not already running:

Linux:
   spin_lock()
       if (try_lock() == failed)
           loop X times
           if (try_lock() == failed)
               sched_op_yield_to(vcpu_num of holder)
               start again;
           endif
       endif

Xen:
     sched_op_yield_to:
          if (vcpu_running(vcpu_num arg))
              do nothing
          else
              vcpu_kick(vcpu_num arg)
              do_yield()
          endif


In my worst case test scenario, I get about 20-36% improvement when the
system is two to three times over provisioned. 

Please provide any feedback. I would like to submit official patch for
SCHEDOP_yield_to in xen.

thanks,
Mukesh

Attachment: spin-lin.diff
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Attachment: spin-xen.diff
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