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From: David Laight <David.Laight@ACULAB.COM>
To: 'Steven Rostedt' <rostedt@goodmis.org>
Cc: "'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>
Subject: RE: ftrace trace_raw_pipe format
Date: Tue, 7 Jan 2020 13:49:40 +0000	[thread overview]
Message-ID: <8b225fdcbe6e4cc7bba302d899e277ae@AcuMS.aculab.com> (raw)
In-Reply-To: <3df0aa9c69ec4d2086b96eb032a1a0df@AcuMS.aculab.com>

After reading the code in kbuffer-parse.c I can now get a sequence of trace entries
with their timestamps.

I think there is a bug in the processing (skipping) of KBUFFER_TYPE_TIME_STAMP
in translate_data().
I assume a 64bit timestamp would follow, and 'data' should only be incremented
by 8 (not 12) as there is an increment by 4 earlier.
I'm pretty sure these are never generated - __next_event() doesn't loop.

It is ~impossible to match this parsing code to the generating code because none
of the constants are in a shared header file.

Back to my original problem:

I've a set of trace files that contain 4 4k blocks each.
The 4 blocks are in time order, but I think there is a big time discontinuity
between the first and second blocks.
The second block has both MISSED_EVENTS and MISSED_STORED set.
My suspicion is that the first block (partially filled) is the final block
from the previous trace and its presence is a bug.
So anything processing the trace must completely ignore the first
block (if the second reports MISSED_EVENTS).

The 4th block is also partial - which is what I expect.

	David

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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


      parent reply	other threads:[~2020-01-07 13:49 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-17 17:44 ftrace trace_raw_pipe format David Laight
2019-12-17 22:34 ` Steven Rostedt
2019-12-17 22:43   ` Steven Rostedt
2019-12-17 22:47   ` Steven Rostedt
2019-12-17 23:36   ` Steven Rostedt
2019-12-17 23:54     ` Steven Rostedt
2019-12-18 16:31   ` Sudip Mukherjee
2019-12-18 17:28   ` David Laight
2019-12-18 17:59     ` Steven Rostedt
2020-01-07 13:49     ` David Laight [this message]

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