[v4,0/3] Timestamp offsets calculation per host CPU

Message

Tzvetomir Stoyanov (VMware) April 9, 2020, 1:28 p.m. UTC

The clock, used for trace time stamps, can vary between CPUs.
When synchronizing host and guest trace time stamps, these
variations could introduce inaccuracy.
The algorithm for host - guest trace time stamps synchronization
is modified to calculate the offset per each host CPU, depending
on the CPU affinity of host tasks, running the guest's VCPUs.
The calculated array per CPU is stored in the trace.dat file, using
TRACECMD_OPTION_TIME_SHIFT option.
The "trace-cmd dump --options" command and tracecmd_init_data() API
are adjusted to read the new format of this option.

In order this per CPU synchronization data to be used when host and
guest files are merged, information about guest VCPUs migration
between host CPUs is needed. This information is extracted from
host trace data, thus the host trace must be recored with "-e sched"
option.

[
 v4 changes:
  - Remove all patches, not related directly to per host CPU timestamp
    offsets calculation, from the patch set.
 v3 changes:
  - Fix allocation of VCPU sched data array when reading sched data
    from host trace file.
]

Tzvetomir Stoyanov (VMware) (3):
  trace-cmd: Time stamp offset per host CPU
  trace-cmd: Add a define to enable per CPU timestamps synchronization
  trace-cmd: Use per CPU synchronization data when calculating
    timestamps offsets

 include/trace-cmd/trace-cmd.h             |   6 +-
 lib/trace-cmd/include/trace-tsync-local.h |  16 +-
 lib/trace-cmd/trace-input.c               | 433 +++++++++++++++++++---
 lib/trace-cmd/trace-timesync.c            | 269 ++++++++++++--
 tracecmd/include/trace-local.h            |   4 +
 tracecmd/trace-dump.c                     |  60 ++-
 tracecmd/trace-record.c                   |  18 +
 tracecmd/trace-tsync.c                    | 144 ++++---
 8 files changed, 757 insertions(+), 193 deletions(-)