[SPARC64]: Make save_stack_trace() more efficient. (85a79353) · Commits · 戴 / test

Doing a 'flushw' every stack trace capture creates so much overhead that it makes lockdep next to unusable. We only care about the frame pointer chain and the function caller program counters, so flush those by hand to the stack frame. This is significantly more efficient than a 'flushw' because: 1) We only save 16 bytes per active register window to the stack. 2) This doesn't push the entire register window context of the current call chain out of the cpu, forcing register window fill traps as we return back down. Note that we can't use 'restore' and 'save' instructions to move around the register windows because that wouldn't work on Niagara processors. They optimize 'save' into a new register window by simply clearing out the registers instead of pulling them in from the on-chip register window backing store. Based upon a report by Tom Callaway. Signed-off-by:

David S. Miller <davem@davemloft.net>

arch/sparc64/kernel/entry.S

+30 −0

Original line number	Diff line number	Diff line
		@@ -1705,6 +1705,36 @@ __flushw_user:
		2: retl
		nop

		/* Flush %fp and %i7 to the stack for all register
		* windows active inside of the cpu. This allows
		* show_stack_trace() to avoid using an expensive
		* 'flushw'.
		*/
		.globl stack_trace_flush
		.type stack_trace_flush,#function
		stack_trace_flush:
		rdpr %pstate, %o0
		wrpr %o0, PSTATE_IE, %pstate

		rdpr %cwp, %g1
		rdpr %canrestore, %g2
		sub %g1, 1, %g3

		1: brz,pn %g2, 2f
		sub %g2, 1, %g2
		wrpr %g3, %cwp
		stx %fp, [%sp + STACK_BIAS + RW_V9_I6]
		stx %i7, [%sp + STACK_BIAS + RW_V9_I7]
		ba,pt %xcc, 1b
		sub %g3, 1, %g3

		2: wrpr %g1, %cwp
		wrpr %o0, %pstate

		retl
		nop
		.size stack_trace_flush,.-stack_trace_flush

		#ifdef CONFIG_SMP
		.globl hard_smp_processor_id
		hard_smp_processor_id:

arch/sparc64/kernel/stacktrace.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -2,13 +2,15 @@
		#include <linux/stacktrace.h>
		#include <linux/thread_info.h>
		#include <asm/ptrace.h>
		#include <asm/stacktrace.h>

		void save_stack_trace(struct stack_trace *trace)
		{
		unsigned long ksp, fp, thread_base;
		struct thread_info *tp = task_thread_info(current);

		flushw_all();
		stack_trace_flush();

		__asm__ __volatile__(
		"mov %%fp, %0"
		: "=r" (ksp)

include/asm-sparc64/stacktrace.h

0 → 100644

+6 −0

Original line number	Diff line number	Diff line
		#ifndef _SPARC64_STACKTRACE_H
		#define _SPARC64_STACKTRACE_H

		extern void stack_trace_flush(void);

		#endif /* _SPARC64_STACKTRACE_H */

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