From: David Laight <David.Laight@ACULAB.COM>
To: 'Steven Rostedt' <rostedt@goodmis.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Peter Wu <peter@lekensteyn.nl>, Jonathan Corbet <corbet@lwn.net>,
Tom Zanussi <zanussi@kernel.org>,
Shuah Khan <shuahkhan@gmail.com>, bpf <bpf@vger.kernel.org>
Subject: RE: [PATCH 00/12 v2] ring-buffer/tracing: Remove disabling of ring buffer while reading trace file
Date: Sat, 21 Mar 2020 19:13:51 +0000 [thread overview]
Message-ID: <2a7f96545945457cade216aa3c736bcc@AcuMS.aculab.com> (raw)
In-Reply-To: <20200319232219.446480829@goodmis.org>
From: Steven Rostedt
> Sent: 19 March 2020 23:22
...
>
> This patch series attempts to satisfy that request, by creating a
> temporary buffer in each of the per cpu iterators to place the
> read event into, such that it can be passed to users without worrying
> about a writer to corrupt the event while it was being written out.
> It also uses the fact that the ring buffer is broken up into pages,
> where each page has its own timestamp that gets updated when a
> writer crosses over to it. By copying it to the temp buffer, and
> doing a "before and after" test of the time stamp with memory barriers,
> can allow the events to be saved.
Does this mean the you will no longer be able to look at a snapshot
of the trace by running 'less trace' (and typically going to the end
to get info for all cpus).
A lot of the time trace is being written far too fast for it to make
any sense to try to read it continuously.
Also, if BPF start using ftrace, no one will be able to use it for
'normal debugging' on such systems.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-03-21 19:14 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-19 23:22 [PATCH 00/12 v2] ring-buffer/tracing: Remove disabling of ring buffer while reading trace file Steven Rostedt
2020-03-19 23:22 ` [PATCH 01/12 v2] selftest/ftrace: Fix function trigger test to handle trace not disabling the tracer Steven Rostedt
2020-03-19 23:22 ` [PATCH 02/12 v2] tracing: Save off entry when peeking at next entry Steven Rostedt
2020-03-20 2:57 ` Masami Hiramatsu
2020-03-26 9:12 ` [tracing] cd8f62b481: BUG:sleeping_function_called_from_invalid_context_at_mm/slab.h kernel test robot
2020-04-01 14:07 ` Masami Hiramatsu
2020-04-01 14:21 ` Steven Rostedt
2020-04-01 15:04 ` Steven Rostedt
2020-04-02 7:19 ` Masami Hiramatsu
2020-04-02 18:14 ` Steven Rostedt
2020-04-03 6:47 ` Masami Hiramatsu
2020-04-03 13:16 ` Steven Rostedt
2020-03-19 23:22 ` [PATCH 03/12 v2] ring-buffer: Have ring_buffer_empty() not depend on tracing stopped Steven Rostedt
2020-03-19 23:22 ` [PATCH 04/12 v2] ring-buffer: Rename ring_buffer_read() to read_buffer_iter_advance() Steven Rostedt
2020-03-19 23:22 ` [PATCH 05/12 v2] ring-buffer: Add page_stamp to iterator for synchronization Steven Rostedt
2020-03-19 23:22 ` [PATCH 06/12 v2] ring-buffer: Have rb_iter_head_event() handle concurrent writer Steven Rostedt
2020-03-19 23:22 ` [PATCH 07/12 v2] ring-buffer: Do not die if rb_iter_peek() fails more than thrice Steven Rostedt
2020-03-19 23:22 ` [PATCH 08/12 v2] ring-buffer: Optimize rb_iter_head_event() Steven Rostedt
2020-03-19 23:22 ` [PATCH 09/12 v2] ring-buffer: Do not disable recording when there is an iterator Steven Rostedt
2020-03-19 23:22 ` [PATCH 10/12 v2] tracing: Do not disable tracing when reading the trace file Steven Rostedt
2020-03-19 23:22 ` [PATCH 11/12 v2] ring-buffer/tracing: Have iterator acknowledge dropped events Steven Rostedt
2020-03-19 23:22 ` [PATCH 12/12 v2] tracing: Have the document reflect that the trace file keeps tracing enabled Steven Rostedt
2020-03-21 19:13 ` David Laight [this message]
2020-03-22 18:07 ` [PATCH 00/12 v2] ring-buffer/tracing: Remove disabling of ring buffer while reading trace file Steven Rostedt
2020-03-27 1:46 ` Steven Rostedt
2020-03-27 10:07 ` David Laight
2020-03-27 14:30 ` Steven Rostedt
2020-03-27 14:56 ` David Laight
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