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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [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@xxxxxxxxxx>) pointed by Stephan Diestelhorst <stephan.diestelhorst@xxxxxxx> - 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(-) _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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