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

arch/mips/kernel/ftrace.c

+7 −7
Original line number Original line Diff line number Diff line
@@ -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, 
		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);