Re: [PATCH 2/3] x86/flush_tlb: try flush_tlb_single one by one in flush_tlb_range

[Alex Shi <alex.shi@intel.com>]

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. :)