From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: rostedt <rostedt@goodmis.org>
Cc: paulmck <paulmck@kernel.org>,
Michael Jeanson <mjeanson@efficios.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Yafang Shao <laoar.shao@gmail.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Michel Lespinasse <walken@google.com>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
Davidlohr Bueso <dbueso@suse.de>, linux-mm <linux-mm@kvack.org>,
Ingo Molnar <mingo@kernel.org>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH 1/2] tracepoints: Add helper to test if tracepoint is enabled in a header
Date: Fri, 25 Sep 2020 11:30:06 -0400 (EDT) [thread overview]
Message-ID: <965650354.69699.1601047806662.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20200925111415.60f5334c@oasis.local.home>
----- On Sep 25, 2020, at 11:14 AM, rostedt rostedt@goodmis.org wrote:
> On Fri, 25 Sep 2020 10:41:56 -0400 (EDT)
> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
>
>> With the current dependencies of tracepoint.h, I would argue that we should
>> only do the trampoline work-around for cases where there is an unavoidable
>> circular dependency, like the case of msr.h. For other headers which don't
>> have circular dependency issues with tracepoint.h, we should use the usual
>> tracepoint instrumentation because not having the trampoline provides better
>> tracing (on) speed and reduces (slightly) code size.
>
> Well, for now, I'm going to add the helper function and have the header
> use cases use that.
>
> A while back ago I had patches that moves the DO_TRACE() work into a
> separate function and with that we probably could have let all
> tracepoints be in headers (as they would all just do a function call to
> the trace algorithm that does the rest of the work). But you balked at
> that because of the added overhead with tracing on.
>
> Anyway, I don't see any issues with the current patch set as is
> (besides the documentation fix, which I already updated locally). And
> will add this to my queue for linux-next.
The only thing I would change in the documentation is to word this as
"here is a trampoline trick which can be used to work-around rare cases
of tracepoint header circular dependency issues" rather than "always use
this when instrumenting a header".
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2020-09-25 15:30 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-24 17:09 [PATCH 0/2] tracing/mm: Add tracepoint_enabled() helper function for headers Steven Rostedt
2020-09-24 17:09 ` [PATCH 1/2] tracepoints: Add helper to test if tracepoint is enabled in a header Steven Rostedt
2020-09-24 17:42 ` Mathieu Desnoyers
2020-09-24 18:19 ` Axel Rasmussen
2020-09-24 18:27 ` Mathieu Desnoyers
2020-09-24 18:30 ` Steven Rostedt
2020-09-24 19:08 ` Mathieu Desnoyers
2020-09-24 19:35 ` Steven Rostedt
2020-09-24 19:40 ` Steven Rostedt
2020-09-24 20:25 ` Mathieu Desnoyers
2020-09-24 20:05 ` Mathieu Desnoyers
2020-09-24 20:13 ` Steven Rostedt
2020-09-24 20:27 ` Mathieu Desnoyers
2020-09-24 20:33 ` Steven Rostedt
2020-09-25 14:41 ` Mathieu Desnoyers
2020-09-25 15:14 ` Steven Rostedt
2020-09-25 15:30 ` Mathieu Desnoyers [this message]
2020-09-25 16:26 ` Steven Rostedt
2020-09-25 17:05 ` Mathieu Desnoyers
2020-09-24 20:04 ` Axel Rasmussen
2020-09-24 17:09 ` [PATCH 2/2] mm/page_ref: Convert the open coded tracepoint enabled to the new helper Steven Rostedt
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