linux-kernel - Re: [PATCH v10 00/25] Speculative page faults

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Date:   Wed, 2 May 2018 16:45:19 +0200
From:   Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:     Punit Agrawal <punit.agrawal@....com>
Cc:     akpm@...ux-foundation.org, mhocko@...nel.org, peterz@...radead.org,
        kirill@...temov.name, ak@...ux.intel.com, dave@...olabs.net,
        jack@...e.cz, Matthew Wilcox <willy@...radead.org>,
        benh@...nel.crashing.org, mpe@...erman.id.au, paulus@...ba.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, hpa@...or.com,
        Will Deacon <will.deacon@....com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        kemi.wang@...el.com, sergey.senozhatsky.work@...il.com,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        David Rientjes <rientjes@...gle.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Ganesh Mahendran <opensource.ganesh@...il.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        haren@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
        npiggin@...il.com, bsingharora@...il.com,
        paulmck@...ux.vnet.ibm.com, Tim Chen <tim.c.chen@...ux.intel.com>,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org
Subject: Re: [PATCH v10 00/25] Speculative page faults



On 02/05/2018 16:17, Punit Agrawal wrote:
> Hi Laurent,
> 
> One query below -
> 
> Laurent Dufour <ldufour@...ux.vnet.ibm.com> writes:
> 
> [...]
> 
>>
>> Ebizzy:
>> -------
>> The test is counting the number of records per second it can manage, the
>> higher is the best. I run it like this 'ebizzy -mTRp'. To get consistent
>> result I repeated the test 100 times and measure the average result. The
>> number is the record processes per second, the higher is the best.
>>
>>   		BASE		SPF		delta	
>> 16 CPUs x86 VM	12405.52	91104.52	634.39%
>> 80 CPUs P8 node 37880.01	76201.05	101.16%
> 
> How do you measure the number of records processed? Is there a specific
> version of ebizzy that reports this? I couldn't find a way to get this
> information with the ebizzy that's included in ltp.

I'm using the original one : http://ebizzy.sourceforge.net/

> 
>>
>> Here are the performance counter read during a run on a 16 CPUs x86 VM:
>>  Performance counter stats for './ebizzy -mRTp':
>>             860074      faults
>>             856866      spf
>>                285      pagefault:spf_pte_lock
>>               1506      pagefault:spf_vma_changed
>>                  0      pagefault:spf_vma_noanon
>>                 73      pagefault:spf_vma_notsup
>>                  0      pagefault:spf_vma_access
>>                  0      pagefault:spf_pmd_changed
>>
>> And the ones captured during a run on a 80 CPUs Power node:
>>  Performance counter stats for './ebizzy -mRTp':
>>             722695      faults
>>             699402      spf
>>              16048      pagefault:spf_pte_lock
>>               6838      pagefault:spf_vma_changed
>>                  0      pagefault:spf_vma_noanon
>>                277      pagefault:spf_vma_notsup
>>                  0      pagefault:spf_vma_access
>>                  0      pagefault:spf_pmd_changed
>>
>> In ebizzy's case most of the page fault were handled in a speculative way,
>> leading the ebizzy performance boost.
> 
> A trial run showed increased fault handling when SPF is enabled on an
> 8-core ARM64 system running 4.17-rc3. I am using a port of your x86
> patch to enable spf on arm64.
> 
> SPF
> ---
> 
> Performance counter stats for './ebizzy -vvvmTRp':
> 
>          1,322,736      faults                                                      
>          1,299,241      software/config=11/                                         
> 
>       10.005348034 seconds time elapsed
> 
> No SPF
> -----
> 
>  Performance counter stats for './ebizzy -vvvmTRp':
> 
>            708,916      faults
>                  0      software/config=11/
> 
>       10.005807432 seconds time elapsed

Thanks for sharing these good numbers !

> Thanks,
> Punit
> 
> [...]
>