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    Subject[PATCH RFC V3 0/4] kvm : Paravirt-spinlock support for KVM guests
    The 4-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.

    The V2 change discussion was in:
    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

    The BASE patch is tip 3.2-rc1 + Jeremy's following patches.
    xadd (https://lkml.org/lkml/2011/10/4/328)
    x86/ticketlocklock (https://lkml.org/lkml/2011/10/12/496).

    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 (4):
    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

    Results:
    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.

    set up :
    Kernel for host/guest : 3.2-rc1 + Jeremy's xadd, pv spinlock patches as BASE

    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

    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: 157.548 (10.624) 156.408 (11.1622) 0.723589
    case 2x: 1110.18 (807.019) 310.96 (105.194) 71.9901
    case 3x: 3110.36 (2408.03) 303.688 (110.474) 90.2362

    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

    BASE BASE+patch %improvement
    mean (sd) mean (sd)
    Scenario A:
    case 1x: 159.725 (47.4906) 159.07 (47.8133) 0.41008
    case 2x: 190.957 (49.2976) 187.273 (50.5469) 1.92923
    case 3x: 226.317 (88.6023) 223.698 (90.4362) 1.15723

    ---
    13 files changed, 454 insertions(+), 112 deletions(-)
    arch/x86/Kconfig | 9 ++
    arch/x86/include/asm/kvm_para.h | 17 +++-
    arch/x86/kernel/kvm.c | 247 +++++++++++++++++++++++++++++++++++++++
    arch/x86/kvm/x86.c | 28 +++++-
    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 | 5 +
    include/linux/kvm_para.h | 1 +
    virt/kvm/kvm_main.c | 7 +
    13 files changed, 452 insertions(+), 112 deletions(-)



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