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  1. Apr 14, 2016
  2. Apr 13, 2016
    • Jisheng Zhang's avatar
      arm64: cpuidle: make arm_cpuidle_suspend() a bit more efficient · b5fda7ed
      Jisheng Zhang authored
      
      
      Currently, we check two pointers: cpu_ops and cpu_suspend on every idle
      state entry. These pointers check can be avoided:
      
      If cpu_ops has not been registered, arm_cpuidle_init() will return
      -EOPNOTSUPP, so arm_cpuidle_suspend() will never have chance to
      run. In other word, the cpu_ops check can be avoid.
      
      Similarly, the cpu_suspend check could be avoided in this hot path by
      moving it into arm_cpuidle_init().
      
      I measured the 4096 * time from arm_cpuidle_suspend entry point to the
      cpu_psci_cpu_suspend entry point. HW platform is Marvell BG4CT STB
      board.
      
      1. only one shell, no other process, hot-unplug secondary cpus, execute
      the following cmd
      
      while true
      do
      	sleep 0.2
      done
      
      before the patch: 1581220ns
      
      after the patch: 1579630ns
      
      reduced by 0.1%
      
      2. only one shell, no other process, hot-unplug secondary cpus, execute
      the following cmd
      
      while true
      do
      	md5sum /tmp/testfile
      	sleep 0.2
      done
      
      NOTE: the testfile size should be larger than L1+L2 cache size
      
      before the patch: 1961960ns
      after the patch: 1912500ns
      
      reduced by 2.5%
      
      So the more complex the system load, the bigger the improvement.
      
      Signed-off-by: default avatarJisheng Zhang <jszhang@marvell.com>
      Acked-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
      Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
      b5fda7ed
    • Kefeng Wang's avatar
      arm64: cpufeature: append additional id_aa64mmfr2 fields to cpufeature · 7d7b4ae4
      Kefeng Wang authored
      
      
      There are some new cpu features which can be identified by id_aa64mmfr2,
      this patch appends all fields of it.
      
      Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
      Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
      7d7b4ae4
  3. Apr 08, 2016
  4. Apr 07, 2016
  5. Apr 06, 2016
  6. Apr 05, 2016
    • Luiz Capitulino's avatar
      kvm: x86: make lapic hrtimer pinned · 61abdbe0
      Luiz Capitulino authored
      
      
      When a vCPU runs on a nohz_full core, the hrtimer used by
      the lapic emulation code can be migrated to another core.
      When this happens, it's possible to observe milisecond
      latency when delivering timer IRQs to KVM guests.
      
      The huge latency is mainly due to the fact that
      apic_timer_fn() expects to run during a kvm exit. It
      sets KVM_REQ_PENDING_TIMER and let it be handled on kvm
      entry. However, if the timer fires on a different core,
      we have to wait until the next kvm exit for the guest
      to see KVM_REQ_PENDING_TIMER set.
      
      This problem became visible after commit 9642d18e. This
      commit changed the timer migration code to always attempt
      to migrate timers away from nohz_full cores. While it's
      discussable if this is correct/desirable (I don't think
      it is), it's clear that the lapic emulation code has
      a requirement on firing the hrtimer in the same core
      where it was started. This is achieved by making the
      hrtimer pinned.
      
      Lastly, note that KVM has code to migrate timers when a
      vCPU is scheduled to run in different core. However, this
      forced migration may fail. When this happens, we can have
      the same problem. If we want 100% correctness, we'll have
      to modify apic_timer_fn() to cause a kvm exit when it runs
      on a different core than the vCPU. Not sure if this is
      possible.
      
      Here's a reproducer for the issue being fixed:
      
       1. Set all cores but core0 to be nohz_full cores
       2. Start a guest with a single vCPU
       3. Trace apic_timer_fn() and kvm_inject_apic_timer_irqs()
      
      You'll see that apic_timer_fn() will run in core0 while
      kvm_inject_apic_timer_irqs() runs in a different core. If
      you get both on core0, try running a program that takes 100%
      of the CPU and pin it to core0 to force the vCPU out.
      
      Signed-off-by: default avatarLuiz Capitulino <lcapitulino@redhat.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      61abdbe0
    • Christian Borntraeger's avatar
      s390/mm/kvm: fix mis-merge in gmap handling · 9c650d09
      Christian Borntraeger authored
      
      
      commit 1e133ab2 ("s390/mm: split arch/s390/mm/pgtable.c") dropped
      some changes from commit a3a92c31 ("KVM: s390: fix mismatch
      between user and in-kernel guest limit") - this breaks KVM for some
      memory sizes (kvm-s390: failed to commit memory region) like
      exactly 2GB.
      
      Cc: Dominik Dingel <dingel@linux.vnet.ibm.com>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Acked-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
      Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      9c650d09
  7. Apr 04, 2016
  8. Apr 03, 2016
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