NAME

       kvmexit - Display the exit_reason and its statistics of each vm exit.

SYNOPSIS

       kvmexit [-h] [-p PID [-v VCPU | -a] ] [-t TID | -T 'TID1,TID2'] [duration]

DESCRIPTION

       Considering  virtual  machines'  frequent  exits can cause performance problems, this tool
       aims to locate the frequent exited reasons and then find solutions to reduce or even avoid
       the exit, by displaying the detail exit reasons and the counts of each vm exit for all vms
       running on one physical machine.

       This tool uses a PERCPU_ARRAY: pcpuArrayA and  a  percpu_hash:  hashA  to  collaboratively
       store  each kvm exit reason and its count. The reason is there exists a rule when one vcpu
       exits and re-enters, it tends to continue to run on the same  physical  cpu  as  the  last
       cycle,  which is also called 'cache hit'. Thus we turn to use a PERCPU_ARRAY to record the
       'cache hit' situation to speed things up; and for other cases, then use a percpu_hash.

       As RAW_TRACEPOINT_PROBE(kvm_exit) consumes less cpu cycles, when this  tool  is  used,  it
       firstly  tries  to  employ  raw  tracepoints  in modules, and if failes, then fall back to
       regular tracepoint.

       Limitation: In view  of  the  hardware-assisted  virtualization  technology  of  different
       architectures, currently we only adapt on vmx in intel.

       Since this uses BPF, only the root user can use this tool.

REQUIREMENTS

       CONFIG_BPF and bcc.

       This also requires Linux 4.7+ (BPF_PROG_TYPE_TRACEPOINT support).

OPTIONS

       -h     Print usage message.

       -p PID Display  process  with this PID only, collpase all tids with exit reasons sorted in
              descending order.

       -v VCPU
              Display this VCPU only for this PID.

       -a ALLTIDS
              Display all TIDS for this PID.

       -t TID Display thread with this TID only with exit reasons sorted in descending order.

       -T 'TID1,TID2'
              Display threads for a union like {395490, 395491}.

       duration
              Duration of display, after sleeping several seconds.

EXAMPLES

       Display kvm exit reasons and statistics for all threads... Hit Ctrl-C to end:
              # kvmexit

       Display kvm exit reasons and statistics for all threads after sleeping 6 secs:
              # kvmexit 6

       Display kvm exit reasons and statistics for PID 1273795 after sleeping 5 secs:
              # kvmexit -p 1273795 5

       Display kvm exit reasons and statistics for PID 1273795 and its all threads after sleeping
       5 secs:
              # kvmexit -p 1273795 5 -a

       Display kvm exit reasons and statistics for PID 1273795 VCPU 0... Hit Ctrl-C to end:
              # kvmexit -p 1273795 -v 0

       Display kvm exit reasons and statistics for PID 1273795 VCPU 0 after sleeping 4 secs:
              # kvmexit -p 1273795 -v 0 4

       Display kvm exit reasons and statistics for TID 1273819 after sleeping 10 secs:
              # kvmexit -t 1273819 10

       Display  kvm  exit reasons and statistics for TIDS ['1273820', '1273819']... Hit Ctrl-C to
       end:
              # kvmexit -T '1273820,1273819'

OVERHEAD

       This traces the "kvm_exit" kernel function, records the exit  reason  and  calculates  its
       counts.  Contrast with filling more vm-exit reason debug entries, this tool is more easily
       and flexibly: the bcc python logic  could  provide  nice  kernel  aggregation  and  custom
       output, the bpf in-kernel percpu_array and percpu_cache further improves performance.

       The  impact  of  using this tool on the host should be negligible. While this tool is very
       efficient, it does affect the guest virtual machine itself, the average  test  results  on
       guest vm are as follows:
                      | cpu cycles
           no TP      |   1127
           regular TP |   1277 (13% downgrade)
           RAW TP     |   1187 (5% downgrade)

       Host: echo 1 > /proc/sys/net/core/bpf_jit_enable

SOURCE

       This is from bcc.

              https://github.com/iovisor/bcc

       Also  look  in  the bcc distribution for a companion _examples.txt file containing example
       usage, output, and commentary for this tool.

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Fei Li <lifei.shirley@bytedance.com>