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    Subject[PATCH RFC V4 0/5] kvm : Paravirt-spinlock support for KVM guests
    The 5-patch series to follow this email extends KVM-hypervisor and Linux guest 
    running on KVM-hypervisor to support pv-ticket spinlocks, based on Xen's implementation.

    One hypercall is introduced in KVM hypervisor,that allows a vcpu to kick
    another vcpu out of halt state.
    The blocking of vcpu is done using halt() in (lock_spinning) slowpath.

    Changes in V4:
    - reabsed to 3.2.0 pre.
    - use APIC ID for kicking the vcpu and use kvm_apic_match_dest for matching. (Avi)
    - fold vcpu->kicked flag into vcpu->requests (KVM_REQ_PVLOCK_KICK) and related
    changes for UNHALT path to make pv ticket spinlock migration friendly. (Avi, Marcello)
    - Added Documentation for CPUID, Hypercall (KVM_HC_KICK_CPU)
    and capabilty (KVM_CAP_PVLOCK_KICK) (Avi)
    - Remove unneeded kvm_arch_vcpu_ioctl_set_mpstate call. (Marcello)
    - cumulative variable type changed (int ==> u32) in add_stat (Konrad)
    - remove unneeded kvm_guest_init for !CONFIG_KVM_GUEST case

    Changes in V3:
    - rebased to 3.2-rc1
    - use halt() instead of wait for kick hypercall.
    - modify kick hyper call to do wakeup halted vcpu.
    - hook kvm_spinlock_init to smp_prepare_cpus call (moved the call out of head##.c).
    - fix the potential race when zero_stat is read.
    - export debugfs_create_32 and add documentation to API.
    - use static inline and enum instead of ADDSTAT macro.
    - add barrier() in after setting kick_vcpu.
    - empty static inline function for kvm_spinlock_init.
    - combine the patches one and two readuce overhead.
    - make KVM_DEBUGFS depends on DEBUGFS.
    - include debugfs header unconditionally.

    Changes in V2:
    - rebased patchesto -rc9
    - synchronization related changes based on Jeremy's changes
    (Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>) pointed by
    Stephan Diestelhorst <stephan.diestelhorst@amd.com>
    - enabling 32 bit guests
    - splitted patches into two more chunks

    Srivatsa Vaddagiri, Suzuki Poulose, Raghavendra K T (5):
    Add debugfs support to print u32-arrays in debugfs
    Add a hypercall to KVM hypervisor to support pv-ticketlocks
    Added configuration support to enable debug information for KVM Guests
    pv-ticketlocks support for linux guests running on KVM hypervisor
    Add documentation on Hypercalls and features used for PV spinlock

    Test Set up :
    The BASE patch is pre 3.2.0 + Jeremy's following patches.
    xadd (https://lkml.org/lkml/2011/10/4/328)
    x86/ticketlocklock (https://lkml.org/lkml/2011/10/12/496).
    Kernel for host/guest : 3.2.0 + Jeremy's xadd, pv spinlock patches as BASE
    (Note:locked add change is not taken yet)

    Results:
    The performance gain is mainly because of reduced busy-wait time.
    From the results we can see that patched kernel performance is similar to
    BASE when there is no lock contention. But once we start seeing more
    contention, patched kernel outperforms BASE (non PLE).
    On PLE machine we do not see greater performance improvement because of PLE
    complimenting halt()

    3 guests with 8VCPU, 4GB RAM, 1 used for kernbench
    (kernbench -f -H -M -o 20) other for cpuhog (shell script while
    true with an instruction)

    scenario A: unpinned

    1x: no hogs
    2x: 8hogs in one guest
    3x: 8hogs each in two guest

    scenario B: unpinned, run kernbench on all the guests no hogs.

    Dbench on PLE machine:
    dbench run on all the guest simultaneously with
    dbench --warmup=30 -t 120 with NRCLIENTS=(8/16/32).

    Result for Non PLE machine :
    ============================
    Machine : IBM xSeries with Intel(R) Xeon(R) x5570 2.93GHz CPU with 8 core , 64GB RAM
    BASE BASE+patch %improvement
    mean (sd) mean (sd)
    Scenario A:
    case 1x: 164.233 (16.5506) 163.584 (15.4598 0.39517
    case 2x: 897.654 (543.993) 328.63 (103.771) 63.3901
    case 3x: 2855.73 (2201.41) 315.029 (111.854) 88.9685

    Dbench:
    Throughput is in MB/sec
    NRCLIENTS BASE BASE+patch %improvement
    mean (sd) mean (sd)
    8 1.774307 (0.061361) 1.725667 (0.034644) -2.74135
    16 1.445967 (0.044805) 1.463173 (0.094399) 1.18993
    32 2.136667 (0.105717) 2.193792 (0.129357) 2.67356

    Result for PLE machine:
    ======================
    Machine : IBM xSeries with Intel(R) Xeon(R) X7560 2.27GHz CPU with 32/64 core, with 8
    online cores and 4*64GB RAM

    Kernbench:
    BASE BASE+patch %improvement
    mean (sd) mean (sd)
    Scenario A:
    case 1x: 161.263 (56.518) 159.635 (40.5621) 1.00953
    case 2x: 190.748 (61.2745) 190.606 (54.4766) 0.0744438
    case 3x: 227.378 (100.215) 225.442 (92.0809) 0.851446

    Scenario B:
    446.104 (58.54 ) 433.12733 (54.476) 2.91

    Dbench:
    Throughput is in MB/sec
    NRCLIENTS BASE BASE+patch %improvement
    mean (sd) mean (sd)
    8 1.101190 (0.875082) 1.700395 (0.846809) 54.4143
    16 1.524312 (0.120354) 1.477553 (0.058166) -3.06755
    32 2.143028 (0.157103) 2.090307 (0.136778) -2.46012

    ---
    V3 kernel Changes:
    https://lkml.org/lkml/2011/11/30/62
    V2 kernel changes :
    https://lkml.org/lkml/2011/10/23/207

    Previous discussions : (posted by Srivatsa V).
    https://lkml.org/lkml/2010/7/26/24
    https://lkml.org/lkml/2011/1/19/212

    Qemu patch for V3:
    http://lists.gnu.org/archive/html/qemu-devel/2011-12/msg00397.html

    Documentation/virtual/kvm/api.txt | 7 +
    Documentation/virtual/kvm/cpuid.txt | 4 +
    Documentation/virtual/kvm/hypercalls.txt | 54 +++++++
    arch/x86/Kconfig | 9 +
    arch/x86/include/asm/kvm_para.h | 16 ++-
    arch/x86/kernel/kvm.c | 249 ++++++++++++++++++++++++++++++
    arch/x86/kvm/x86.c | 37 ++++-
    arch/x86/xen/debugfs.c | 104 -------------
    arch/x86/xen/debugfs.h | 4 -
    arch/x86/xen/spinlock.c | 2 +-
    fs/debugfs/file.c | 128 +++++++++++++++
    include/linux/debugfs.h | 11 ++
    include/linux/kvm.h | 1 +
    include/linux/kvm_host.h | 1 +
    include/linux/kvm_para.h | 1 +
    15 files changed, 514 insertions(+), 114 deletions(-)



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