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>