From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@amacapital.net>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 5/6 v3] ftrace/x86_32: Add -mfentry support to x86_32 with DYNAMIC_FTRACE set
Date: Mon, 20 Mar 2017 09:02:17 -0500 [thread overview]
Message-ID: <20170320140217.p27nu2hlx3e2p2kc@treble> (raw)
In-Reply-To: <20170318211149.565075180@goodmis.org>
On Sat, Mar 18, 2017 at 05:09:28PM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
>
> x86_64 has had fentry support for some time. I did not add support to x86_32
> as I was unsure if it will be used much in the future. It is still very much
> used, and there's issues with function graph tracing with gcc playing around
> with the mcount frames, causing function graph to panic. The fentry code
> does not have this issue, and is able to cope as there is no frame to mess
> up.
>
> Note, this only add support for fentry when DYNAMIC_FTRACE is set. There's
> really no reason to not have that set, because the performance of the
> machine drops significantly when it's not enabled. I only keep
> !DYNAMIC_FTRACE around to test it off, as there's still some archs that have
> FTRACE but not DYNAMIC_FTRACE.
>
> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
--
Josh
next prev parent reply other threads:[~2017-03-20 14:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-18 21:09 [PATCH 0/6 v3] [GIT PULL] ftrace/x86: Ftrace cleanup and add support for -mfentry on x86_32 Steven Rostedt
2017-03-18 21:09 ` [PATCH 1/6 v3] ftrace/x86_64: Rename mcount_64.S to ftrace_64.S Steven Rostedt
2017-03-18 21:09 ` [PATCH 2/6 v3] ftrace/x86_32: Move the ftrace specific code out of entry_32.S Steven Rostedt
2017-03-18 21:09 ` [PATCH 3/6 v3] ftrace/x86_32: Add stack frame pointer to ftrace_caller Steven Rostedt
2017-03-18 21:09 ` [PATCH 4/6 v3] ftrace/x86_32: Clean up ftrace_regs_caller Steven Rostedt
2017-03-20 14:01 ` Josh Poimboeuf
2017-03-18 21:09 ` [PATCH 5/6 v3] ftrace/x86_32: Add -mfentry support to x86_32 with DYNAMIC_FTRACE set Steven Rostedt
2017-03-20 14:02 ` Josh Poimboeuf [this message]
2017-03-18 21:09 ` [PATCH 6/6 v3] ftrace/x86: Use Makefile logic instead of #ifdef of compling ftrace_*.o Steven Rostedt
2017-03-20 14:04 ` Josh Poimboeuf
2017-03-22 0:56 ` Steven Rostedt
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