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Commit 0ad6e3c5 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

x86: Speed up ___preempt_schedule*() by using THUNK helpers 



___preempt_schedule() does SAVE_ALL/RESTORE_ALL but this is
suboptimal, we do not need to save/restore the callee-saved
register. And we already have arch/x86/lib/thunk_*.S which
implements the similar asm wrappers, so it makes sense to
redefine ___preempt_schedule() as "THUNK ..." and remove
preempt.S altogether.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarAndy Lutomirski <luto@amacapital.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140921184153.GA23727@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent f3670394

arch/x86/kernel/Makefile

+0 −2
Original line number Diff line number Diff line
@@ -39,8 +39,6 @@ obj-y += tsc.o tsc_msr.o io_delay.o rtc.o 
obj-y			+= pci-iommu_table.o

obj-y			+= resource.o



obj-$(CONFIG_PREEMPT)	+= preempt.o



obj-y				+= process.o

obj-y				+= i387.o xsave.o

obj-y				+= ptrace.o

arch/x86/kernel/preempt.S

deleted100644 → 0
+0 −25
Original line number Diff line number Diff line 


#include <linux/linkage.h>

#include <asm/dwarf2.h>

#include <asm/asm.h>

#include <asm/calling.h>



ENTRY(___preempt_schedule)

	CFI_STARTPROC

	SAVE_ALL

	call preempt_schedule

	RESTORE_ALL

	ret

	CFI_ENDPROC



#ifdef CONFIG_CONTEXT_TRACKING



ENTRY(___preempt_schedule_context)

	CFI_STARTPROC

	SAVE_ALL

	call preempt_schedule_context

	RESTORE_ALL

	ret

	CFI_ENDPROC



#endif

arch/x86/lib/thunk_32.S

+16 −4
Original line number Diff line number Diff line
@@ -7,16 +7,19 @@ 
	#include <linux/linkage.h>

	#include <asm/asm.h>



#ifdef CONFIG_TRACE_IRQFLAGS

	/* put return address in eax (arg1) */

	.macro thunk_ra name,func

	.macro THUNK name, func, put_ret_addr_in_eax=0

	.globl \name

\name:

	pushl %eax

	pushl %ecx

	pushl %edx



	.if \put_ret_addr_in_eax

	/* Place EIP in the arg1 */

	movl 3*4(%esp), %eax

	.endif



	call \func

	popl %edx

	popl %ecx
@@ -25,6 +28,15 @@ 
	_ASM_NOKPROBE(\name)

	.endm



	thunk_ra trace_hardirqs_on_thunk,trace_hardirqs_on_caller

	thunk_ra trace_hardirqs_off_thunk,trace_hardirqs_off_caller

#ifdef CONFIG_TRACE_IRQFLAGS

	THUNK trace_hardirqs_on_thunk,trace_hardirqs_on_caller,1

	THUNK trace_hardirqs_off_thunk,trace_hardirqs_off_caller,1

#endif



#ifdef CONFIG_PREEMPT

	THUNK ___preempt_schedule, preempt_schedule

#ifdef CONFIG_CONTEXT_TRACKING

	THUNK ___preempt_schedule_context, preempt_schedule_context

#endif

#endif

arch/x86/lib/thunk_64.S

+7 −0
Original line number Diff line number Diff line
@@ -38,6 +38,13 @@ 
	THUNK lockdep_sys_exit_thunk,lockdep_sys_exit

#endif



#ifdef CONFIG_PREEMPT

	THUNK ___preempt_schedule, preempt_schedule

#ifdef CONFIG_CONTEXT_TRACKING

	THUNK ___preempt_schedule_context, preempt_schedule_context

#endif

#endif



	/* SAVE_ARGS below is used only for the .cfi directives it contains. */

	CFI_STARTPROC

	SAVE_ARGS