Messages in this thread | | | Date | Tue, 29 Jan 2002 01:04:20 +0100 | From | Pavel Machek <> | Subject | Re: [patch] [sched] x86 idle thread should clear %fs, %gs |
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Hi!
> so it appears that this lowlevel x86 performance bug(?) is more than 11 > years old! :-)
Probably 386's were not optimized for %fs==%gs==0 case?
BTW does it really make a difference for the CPU? Pavel
> @@ -2803,9 +2803,10 @@ > load_TR(nr); > load_LDT(&init_mm); > > - /* > - * Clear all 6 debug registers: > - */ > + /* Clear %fs and %gs. */ > + asm volatile ("xorl %eax, %eax; movl %eax, %fs; movl %eax, %gs"); > + > + /* Clear all 6 debug registers: */ > > #define CD(register) __asm__("movl %0,%%db" #register ::"r"(0) );
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