From: Steven Rostedt <rostedt@goodmis.org>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH 1/5] [PATCH 1/5] function-graph/x86: replace unbalanced ret with jmp
Date: Tue, 13 Oct 2009 17:26:50 -0400 [thread overview]
Message-ID: <1255469210.7113.2436.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <20091013212126.GA8039@Krystal>
On Tue, 2009-10-13 at 17:21 -0400, Mathieu Desnoyers wrote:
> > What it was:
> >
> > call function
> > function:
> > call mcount
> > mcount:
> > call ftrace_entry
>
> Can we manage to change this call
Note, that call jumps to C code.
>
> > ftrace_entry:
> > mess up with return code of caller
> > ret
>
> .. and this ret for 2 jmp instructions too ?
The code is all in C, and it too calls functions. Not sure where this
helps out any. The ret here matches their calls. Thus the prediction
will work.
>
> Given that we have no choice but to kill call/ret prediction logic, I
> think it might be good to try to use this logic as little as possible
> (by favoring jmp jmp over call/ret when the return target is invariant).
>
> That's just an idea, benchmarks could prove me right/wrong.
I don't see how this would help. And I'm not about to waste time
experimenting. What's the rational?
-- Steve
next prev parent reply other threads:[~2009-10-13 21:28 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-13 20:33 [PATCH 0/5] [GIT PULL][2.6.33] tracing: various updates Steven Rostedt
2009-10-13 20:33 ` [PATCH 1/5] [PATCH 1/5] function-graph/x86: replace unbalanced ret with jmp Steven Rostedt
2009-10-13 20:47 ` Mathieu Desnoyers
2009-10-13 21:10 ` Steven Rostedt
2009-10-13 21:21 ` Mathieu Desnoyers
2009-10-13 21:26 ` Steven Rostedt [this message]
2009-10-13 22:32 ` Mathieu Desnoyers
2009-10-13 21:02 ` Frederic Weisbecker
2009-10-13 21:12 ` Steven Rostedt
2009-10-13 22:26 ` Frederic Weisbecker
2009-10-14 6:58 ` [tip:tracing/core] function-graph/x86: Replace " tip-bot for Steven Rostedt
2009-10-13 20:33 ` [PATCH 2/5] [PATCH 2/5] tracing: export symbols for kernel lock tracepoints Steven Rostedt
2009-10-13 20:43 ` Frederic Weisbecker
2009-10-13 21:14 ` Steven Rostedt
2009-10-13 20:33 ` [PATCH 3/5] [PATCH 3/5] tracing: support multiple pids in set_pid_ftrace file Steven Rostedt
2009-10-14 6:58 ` [tip:tracing/core] tracing: Support " tip-bot for jolsa@redhat.com
2009-10-13 20:33 ` [PATCH 4/5] [PATCH 4/5] tracing: enable records during the module load Steven Rostedt
2009-10-14 6:59 ` [tip:tracing/core] tracing: Enable " tip-bot for Jiri Olsa
2009-10-13 20:33 ` [PATCH 5/5] [PATCH 5/5] tracing: enabling "__cold" functions Steven Rostedt
2009-10-14 6:59 ` [tip:tracing/core] tracing: Enable " tip-bot for Jiri Olsa
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1255469210.7113.2436.camel@gandalf.stny.rr.com \
--to=rostedt@goodmis.org \
--cc=akpm@linux-foundation.org \
--cc=fweisbec@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@polymtl.ca \
--cc=mingo@elte.hu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®