Commit 9a620a55 authored by Wu Zhangjin's avatar Wu Zhangjin Committed by Ralf Baechle

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: default avatarWu 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: default avatarRalf Baechle <ralf@duck.linux-mips.net>
parent 52bd080d
...@@ -200,19 +200,17 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr, ...@@ -200,19 +200,17 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
int faulted; int faulted;
/* /*
* For module, move the ip from calling site of mcount to the * For module, move the ip from calling site of mcount after the
* instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
* kernel, move to the instruction "move ra, at"(offset is 12) * 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} * search the text until finding the non-store instruction or "s{d,w}
* ra, offset(sp)" instruction * ra, offset(sp)" instruction
*/ */
do { do {
ip -= 4;
/* get the code at "ip": code = *(unsigned int *)ip; */ /* get the code at "ip": code = *(unsigned int *)ip; */
safe_load_code(code, ip, faulted); safe_load_code(code, ip, faulted);
...@@ -226,7 +224,9 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr, ...@@ -226,7 +224,9 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
if ((code & S_R_SP) != S_R_SP) if ((code & S_R_SP) != S_R_SP)
return parent_addr; 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); sp = fp + (code & OFFSET_MASK);
......
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