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From: Alex Shi <alex.shi@intel.com>
To: Nick Piggin <npiggin@gmail.com>
Cc: Borislav Petkov <bp@amd64.org>,
	andi.kleen@intel.com, tim.c.chen@linux.intel.com,
	jeremy@goop.org, chrisw@sous-sol.org, akataria@vmware.com,
	tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	rostedt@goodmis.org, fweisbec@gmail.com, riel@redhat.com,
	luto@mit.edu, avi@redhat.com, len.brown@intel.com,
	paul.gortmaker@windriver.com, dhowells@redhat.com,
	fenghua.yu@intel.com, yinghai@kernel.org, cpw@sgi.com,
	steiner@sgi.com, linux-kernel@vger.kernel.org,
	yongjie.ren@intel.com
Subject: Re: [PATCH 2/3] x86/flush_tlb: try flush_tlb_single one by one in flush_tlb_range
Date: Wed, 02 May 2012 21:24:41 +0800	[thread overview]
Message-ID: <4FA13599.7080308@intel.com> (raw)
In-Reply-To: <CAPa8GCDhGfuYEemdsnUZwh=O6Nco1PH1JgiruvWw3400yz9S8w@mail.gmail.com>

On 05/02/2012 09:04 PM, Nick Piggin wrote:

> On 2 May 2012 21:38, Alex Shi <alex.shi@intel.com> wrote:
>> On 05/02/2012 05:38 PM, Borislav Petkov wrote:
>>
>>> On Wed, May 02, 2012 at 05:24:09PM +0800, Alex Shi wrote:
>>>> For some of scenario, above equation can be modified as:
>>>> (512 - X) * 100ns(assumed TLB refill cost) = X * 140ns(assumed invlpg cost)
> 
> It should not be that optimistic, because that equation assumes every
> unflushed entry saves a TLB refill too.
> 


Yes, it is just ideal scenario to do analysis. In the code, the judgment
depends on the 'active entries' instead of the fixed TLB line number.

active entries = min(this process's page number, TLB line number)

> I think it is always a good idea to make such fundamental primitives
> cheaper though.
> 



  parent reply	other threads:[~2012-05-02 13:25 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-28  8:51 [PATCH 0/3] TLB flush range optimization Alex Shi
2012-04-28  8:51 ` [PATCH 1/3] x86/tlb_info: get last level TLB entry number of CPU Alex Shi
2012-04-29 13:55   ` Borislav Petkov
2012-04-30  4:25     ` Alex Shi
2012-04-30 10:45       ` Borislav Petkov
2012-04-28  8:51 ` [PATCH 2/3] x86/flush_tlb: try flush_tlb_single one by one in flush_tlb_range Alex Shi
2012-04-30 10:54   ` Borislav Petkov
2012-05-02  9:24     ` Alex Shi
2012-05-02  9:38       ` Borislav Petkov
2012-05-02 11:38         ` Alex Shi
2012-05-02 13:04           ` Nick Piggin
2012-05-02 13:15             ` Alex Shi
2012-05-02 13:24             ` Alex Shi [this message]
2012-05-06  2:55             ` Alex Shi
2012-05-02 13:44           ` Borislav Petkov
2012-05-03  9:15             ` Alex Shi
2012-05-04  2:24   ` Ren, Yongjie
2012-05-04  5:46     ` Alex Shi
2012-04-28  8:51 ` [PATCH 3/3] x86/tlb: fall back to flush all when meet a THP large page Alex Shi
  -- strict thread matches above, loose matches on Subject: below --
2012-04-28  8:50 [PATCH 1/3] x86/tlb_info: get last level TLB entry number of CPU Alex Shi
2012-04-28  8:50 ` [PATCH 2/3] x86/flush_tlb: try flush_tlb_single one by one in flush_tlb_range Alex Shi
2012-05-02 15:21   ` Rik van Riel

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