linux-kernel - Re: [PATCH v4 5/7] x86/tlb: add tlb flush all factor for specific CPU

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Date:	Fri, 11 May 2012 08:49:33 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	rob@...dley.net, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, arnd@...db.de, rostedt@...dmis.org,
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Subject: Re: [PATCH v4 5/7] x86/tlb: add tlb flush all factor for specific
 CPU

On 05/10/2012 05:38 PM, Peter Zijlstra wrote:

> On Thu, 2012-05-10 at 13:00 +0800, Alex Shi wrote:
> 
> 
>> +void intel_tlb_flushall_factor_set(struct cpuinfo_x86 *c)
>> +{
>> +       if (!cpu_has_invlpg) {
>> +               tlb_flushall_factor = -1;
>> +               return;
>> +       }
> 
> ...
> 
>> +       if (!cpu_has_invlpg || vma->vm_flags & VM_HUGETLB
>> +                       || tlb_flushall_factor == (u16)TLB_FLUSH_ALL)
>> {
>>  flush_all: 
> 
> Since you set tlb_flushall_factor (I'd have called it _shift) to -1
> when !invlpg there's a redundant check in there.
> 



NO, the first judgement is from CPU. But second '-1' is may from user
setting in sysfs.
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