Re: [PATCH v3 00/20] Speculative page faults

From	Laurent Dufour <ldufour@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 00/20] Speculative page faults
Date	2017-09-28 14:30 +0200
Message-ID	<uuG71-vR-45@gated-at.bofh.it> (permalink)
References	<utEqC-mA-23@gated-at.bofh.it> <utL8J-4Uf-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hi Andrew,

On 26/09/2017 01:34, Andrew Morton wrote:
> On Mon, 25 Sep 2017 09:27:43 -0700 Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> 
>> On Mon, Sep 18, 2017 at 12:15 AM, Laurent Dufour
>> <ldufour@linux.vnet.ibm.com> wrote:
>>> Despite the unprovable lockdep warning raised by Sergey, I didn't get any
>>> feedback on this series.
>>>
>>> Is there a chance to get it moved upstream ?
>>
>> what is the status ?
>> We're eagerly looking forward for this set to land,
>> since we have several use cases for tracing that
>> will build on top of this set as discussed at Plumbers.
> 
> There has been sadly little review and testing so far :(
> 
> I'll be taking a close look at it all over the next couple of weeks.
> 
> One terribly important thing (especially for a patchset this large and
> intrusive) is the rationale for merging it: the justification, usually
> in the form of end-user benefit.
> 
> Laurent's [0/n] provides some nice-looking performance benefits for
> workloads which are chosen to show performance benefits(!) but, alas,
> no quantitative testing results for workloads which we may suspect will
> be harmed by the changes(?).  Even things as simple as impact upon
> single-threaded pagefault-intensive workloads and its effect upon
> CONFIG_SMP=n .text size?

I forgot to mention in my previous email the impact on the .text section.

Here are the metrics I got :

.text size	UP		SMP		Delta
4.13-mmotm	8444201		8964137		6.16%
'' +spf		8452041		8971929		6.15%
	Delta	0.09%		0.09%	

No major impact as you could see.

Thanks,
Laurent

> If you have additional usecases then please, spell them out for us in
> full detail so we can better understand the benefits which this
> patchset provides.
>

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Re: [PATCH v3 00/20] Speculative page faults Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-09-28 14:30 +0200
  Re: [PATCH v3 00/20] Speculative page faults Andrew Morton <akpm@linux-foundation.org> - 2017-09-28 22:40 +0200
    Re: [PATCH v3 00/20] Speculative page faults Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-09-29 17:30 +0200

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