linux-kernel - Re: [PATCH 2/3] x86/flush_tlb: try flush_tlb_single one by one in flush_tlb

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Message-ID: <4FA24CA7.2070107@intel.com>
Date:	Thu, 03 May 2012 17:15:19 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Borislav Petkov <bp@...64.org>
CC:	andi.kleen@...el.com, tim.c.chen@...ux.intel.com, jeremy@...p.org,
	chrisw@...s-sol.org, akataria@...are.com, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, rostedt@...dmis.org,
	fweisbec@...il.com, riel@...hat.com, luto@....edu, avi@...hat.com,
	len.brown@...el.com, paul.gortmaker@...driver.com,
	dhowells@...hat.com, fenghua.yu@...el.com, yinghai@...nel.org,
	cpw@....com, steiner@....com, linux-kernel@...r.kernel.org,
	yongjie.ren@...el.com
Subject: Re: [PATCH 2/3] x86/flush_tlb: try flush_tlb_single one by one in
 flush_tlb_range

On 05/02/2012 09:44 PM, Borislav Petkov wrote:

> On Wed, May 02, 2012 at 07:38:47PM +0800, Alex Shi wrote:
>>> Are you saying you want to have this setting per family?
>>
>> Set it according to CPU type is more precise, but looks ugly.
> 
> By "CPU type" do you mean microarchitecture here?


Yes.

> 
>> I am wondering if it worth to do. Maybe conservative selection is
>> acceptable?
> 
> Well, as I said earlier, I'd run it on a couple of different machines
> and make FLUSHALL_BAR configurable from userspace - this way you have
> real, solid data instead of guessing the exact number.


Consider different CPU type has different balance point, I has another
patch will add a interface for tuning.

> 
>>> Also, have you run your patches with other benchmarks beside your
>>> microbenchmark, say kernbench, SPEC<something>, i.e. some other
>>> multithreaded benchmark touching shared memory? Are you seeing any
>>> improvement there?
>>
>> I tested oltp reading and specjbb2005 with openjdk. They should not much
>> flush_tlb_range calling. So, no clear improvement.
>> Do you know benchmarks which cause enough flush_tlb_range?
> 
> Not really. Probably get a couple of benchmarks and count
> flush_tlb_range calls with trace_printk or perf probe? :-)


perf probe is enough. :)
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