libtracecmd: Just save timestamps and not the records in iterators
The iterators cache the records via a tracecmd_peek_data() to find the next
CPU record to use. The problem is that the callback() may do a
tracecmd_read_data() (the function graph plugin does) and this may
invalidate the cached record. It would require refreshing every record of
every cached CPU after every callback, which can be expensive.
Since only the timestamps of the records are needed, simply cache the
timestamp of the record to find which is the next CPU record to use. After
finding the CPU that has the earliest timestamp, do a tracecmd_peek_data()
test again to make sure the timestamp still matches the record. If it does,
then simply use that record, if not, refresh the timestamp for that CPU and
try again.
Link: https://lore.kernel.org/linux-trace-devel/20240111222201.154686-4-rostedt@goodmis.org
Fixes: 2cb6cc2f4 ("tracecmd library: Add tracecmd_iterate_events()")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
1 file changed