linux-kernel - [tip:x86/asm] ftrace: Only allocate the ret

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Message-ID: <tip-daa460a88c09b26b68e8b017de589c217e901afb@git.kernel.org>
Date:   Wed, 24 Aug 2016 06:03:55 -0700
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     jpoimboe@...hat.com, keescook@...omium.org, hpa@...or.com,
        rostedt@...dmis.org, mingo@...nel.org, tglx@...utronix.de,
        luto@...nel.org, bp@...en8.de, fweisbec@...il.com,
        brgerst@...il.com, dvlasenk@...hat.com, luto@...capital.net,
        torvalds@...ux-foundation.org, peterz@...radead.org,
        byungchul.park@....com, linux-kernel@...r.kernel.org,
        nilayvaish@...il.com
Subject: [tip:x86/asm] ftrace: Only allocate the ret_stack 'fp' field when
 needed

Commit-ID:  daa460a88c09b26b68e8b017de589c217e901afb
Gitweb:     http://git.kernel.org/tip/daa460a88c09b26b68e8b017de589c217e901afb
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Fri, 19 Aug 2016 06:52:56 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 24 Aug 2016 12:15:14 +0200

ftrace: Only allocate the ret_stack 'fp' field when needed

This saves some memory when HAVE_FUNCTION_GRAPH_FP_TEST isn't defined.
On x86_64 with newer versions of gcc which have -mfentry, it saves 400
bytes per task.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Acked-by: Steven Rostedt <rostedt@...dmis.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Byungchul Park <byungchul.park@....com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Nilay Vaish <nilayvaish@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/5c7747d9ea7b5cb47ef0a8ce8a6cea6bf7aa94bf.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 include/linux/ftrace.h               | 2 ++
 kernel/trace/trace_functions_graph.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 7d565af..4ad9ccc 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -795,7 +795,9 @@ struct ftrace_ret_stack {
 	unsigned long func;
 	unsigned long long calltime;
 	unsigned long long subtime;
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	unsigned long fp;
+#endif
 };
 
 /*
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index fc173cd..0e03ed0 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -171,7 +171,9 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
 	current->ret_stack[index].func = func;
 	current->ret_stack[index].calltime = calltime;
 	current->ret_stack[index].subtime = 0;
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	current->ret_stack[index].fp = frame_pointer;
+#endif
 	*depth = current->curr_ret_stack;
 
 	return 0;