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x86/process: Optimize TIF_NOTSC switch 

Provide and use a toggle helper instead of doing it with a branch.

x86_64: arch/x86/kernel/process.o
text	   data	    bss	    dec	    hex
3008	   8577	     16	  11601	   2d51 Before
2976       8577      16	  11569	   2d31 After

i386: arch/x86/kernel/process.o
text	   data	    bss	    dec	    hex
2925	   8673	      8	  11606	   2d56 Before
2893	   8673       8	  11574	   2d36 After

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Link: http://lkml.kernel.org/r/20170214081104.9244-4-khuey@kylehuey.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2017-02-14 00:11:04 -08:00
parent b9894a2f5b
commit 5a920155e3
2 changed files with 14 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
arch/x86/include/asm/tlbflush.h
View File

@ -110,6 +110,16 @@ static inline void cr4_clear_bits(unsigned long mask)
}
}
static inline void cr4_toggle_bits(unsigned long mask)
{
unsigned long cr4;
cr4 = this_cpu_read(cpu_tlbstate.cr4);
cr4 ^= mask;
this_cpu_write(cpu_tlbstate.cr4, cr4);
__write_cr4(cr4);
}
/* Read the CR4 shadow. */
static inline unsigned long cr4_read_shadow(void)
{

22
arch/x86/kernel/process.c
View File

@ -124,11 +124,6 @@ void flush_thread(void)
fpu__clear(&tsk->thread.fpu);
}
static void hard_disable_TSC(void)
{
cr4_set_bits(X86_CR4_TSD);
}
void disable_TSC(void)
{
preempt_disable();
@ -137,15 +132,10 @@ void disable_TSC(void)
* Must flip the CPU state synchronously with
* TIF_NOTSC in the current running context.
*/
hard_disable_TSC();
cr4_set_bits(X86_CR4_TSD);
preempt_enable();
}
static void hard_enable_TSC(void)
{
cr4_clear_bits(X86_CR4_TSD);
}
static void enable_TSC(void)
{
preempt_disable();
@ -154,7 +144,7 @@ static void enable_TSC(void)
* Must flip the CPU state synchronously with
* TIF_NOTSC in the current running context.
*/
hard_enable_TSC();
cr4_clear_bits(X86_CR4_TSD);
preempt_enable();
}
@ -233,12 +223,8 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
}
if ((tifp ^ tifn) & _TIF_NOTSC) {
if (tifn & _TIF_NOTSC)
hard_disable_TSC();
else
hard_enable_TSC();
}
if ((tifp ^ tifn) & _TIF_NOTSC)
cr4_toggle_bits(X86_CR4_TSD);
}
/*