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[v2,0/4] trace-cmd: Align guest TSC calculation with the kernel

Message ID 20211014150204.2485499-1-tz.stoyanov@gmail.com (mailing list archive)
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Series trace-cmd: Align guest TSC calculation with the kernel | expand

Message

Tzvetomir Stoyanov (VMware) Oct. 14, 2021, 3:02 p.m. UTC 
The formula for calculating guest TSC clock, used in the kernel is:
 guest_tsc = tsc-offset + (host_tsc * tsc-scaling-ratio) >> tsc-scaling-ratio-frac-bits
Current trace-cmd implementation does not take into account fraction
bits, when calculating guest clock offset in case of a clock scaling.
Additional logic is added, to use the same formula in trace-cmd. The changes
are backward compatible with trace-cmd 2.9.

The changes are not tested with a kernel that has guest clock scaling enabled.
The goal of the patch set is to extend the time sync option, saved in the
guest trace.dat file, with all needed data used in the kernel for guest TSC
calculations.

v2 changes:
 - Use strcmp() instead of strncmp() when searching for KVM debug files.
 - Added more comments.
 - Code clean ups.

Tzvetomir Stoyanov (VMware) (4):
  trace-cmd library: Do not use strncmp() when searching for KVM debug
    files
  trace-cmd library: Extend host-guest time sync with fraction bits
  trace-cmd library: Read and use fraction bits from
    TRACECMD_OPTION_TIME_SHIFT
  trace-cmd: Dump fraction bits from TRACECMD_OPTION_TIME_SHIFT

 .../include/private/trace-cmd-private.h       |   4 +-
 lib/trace-cmd/include/trace-tsync-local.h     |   7 +-
 lib/trace-cmd/trace-input.c                   |  79 +++++++-------
 lib/trace-cmd/trace-timesync-kvm.c            |  62 +++++++----
 lib/trace-cmd/trace-timesync-ptp.c            |   4 +-
 lib/trace-cmd/trace-timesync.c                |  55 ++++++++--
 tracecmd/trace-dump.c                         | 102 +++++++++++++-----
 7 files changed, 210 insertions(+), 103 deletions(-)