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authorWu Zhangjin <wuzhangjin@gmail.com>2011-01-19 19:28:27 (GMT)
committerRalf Baechle <ralf@linux-mips.org>2011-03-14 20:07:24 (GMT)
commit9a620a559be65023b5fd5d0eaf37dae884c4f404 (patch)
tree3c7e7d69c6ee14088ac8bf08499d9e8afce2710c
parent52bd080d5c87af556bf71e3b07bdd8586166c43b (diff)
MIPS, Tracing: Speed up function graph tracer
This simply moves the "ip-=4" statement down to the end of the do { ... } while (...); loop, which reduces one unneeded subtration and the subsequent memory loading and comparison. Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/2006/ Signed-off-by: Ralf Baechle <ralf@duck.linux-mips.net>
-rw-r--r--arch/mips/kernel/ftrace.c14
1 files changed, 7 insertions, 7 deletions
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 5a84a1f..635c1dc 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -200,19 +200,17 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
int faulted;
/*
- * For module, move the ip from calling site of mcount to the
- * instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
- * kernel, move to the instruction "move ra, at"(offset is 12)
+ * For module, move the ip from calling site of mcount after the
+ * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
+ * kernel, move after the instruction "move ra, at"(offset is 16)
*/
- ip = self_addr - (in_module(self_addr) ? 20 : 12);
+ ip = self_addr - (in_module(self_addr) ? 24 : 16);
/*
* search the text until finding the non-store instruction or "s{d,w}
* ra, offset(sp)" instruction
*/
do {
- ip -= 4;
-
/* get the code at "ip": code = *(unsigned int *)ip; */
safe_load_code(code, ip, faulted);
@@ -226,7 +224,9 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
if ((code & S_R_SP) != S_R_SP)
return parent_addr;
- } while (((code & S_RA_SP) != S_RA_SP));
+ /* Move to the next instruction */
+ ip -= 4;
+ } while ((code & S_RA_SP) != S_RA_SP);
sp = fp + (code & OFFSET_MASK);

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