1. 17 Oct, 2013 2 commits
    • Christoffer Dall's avatar
      KVM: ARM: Update comments for kvm_handle_wfi · 86ed81aa
      Christoffer Dall authored
      Update comments to reflect what is really going on and add the TWE bit
      to the comments in kvm_arm.h.
      
      Also renames the function to kvm_handle_wfx like is done on arm64 for
      consistency and uber-correctness.
      Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
      86ed81aa
    • Marc Zyngier's avatar
      ARM: KVM: Yield CPU when vcpu executes a WFE · 58d5ec8f
      Marc Zyngier authored
      On an (even slightly) oversubscribed system, spinlocks are quickly
      becoming a bottleneck, as some vcpus are spinning, waiting for a
      lock to be released, while the vcpu holding the lock may not be
      running at all.
      
      This creates contention, and the observed slowdown is 40x for
      hackbench. No, this isn't a typo.
      
      The solution is to trap blocking WFEs and tell KVM that we're
      now spinning. This ensures that other vpus will get a scheduling
      boost, allowing the lock to be released more quickly. Also, using
      CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT slightly improves the performance
      when the VM is severely overcommited.
      
      Quick test to estimate the performance: hackbench 1 process 1000
      
      2xA15 host (baseline):	1.843s
      
      2xA15 guest w/o patch:	2.083s
      4xA15 guest w/o patch:	80.212s
      8xA15 guest w/o patch:	Could not be bothered to find out
      
      2xA15 guest w/ patch:	2.102s
      4xA15 guest w/ patch:	3.205s
      8xA15 guest w/ patch:	6.887s
      
      So we go from a 40x degradation to 1.5x in the 2x overcommit case,
      which is vaguely more acceptable.
      Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
      Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
      58d5ec8f
  2. 16 Oct, 2013 2 commits
  3. 15 Oct, 2013 1 commit
  4. 14 Oct, 2013 7 commits
  5. 13 Oct, 2013 3 commits
  6. 10 Oct, 2013 1 commit
  7. 03 Oct, 2013 8 commits
  8. 02 Oct, 2013 5 commits
  9. 30 Sep, 2013 7 commits
  10. 24 Sep, 2013 4 commits