linux-kernel - Re: [v5,22/22] powerpc/mm: Add speculative page fault

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Message-ID: <20171106102726.GB1298@jagdpanzerIV>
Date:   Mon, 6 Nov 2017 19:27:26 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Laurent Dufour <ldufour@...ux.vnet.ibm.com>
Cc:     kemi <kemi.wang@...el.com>, paulmck@...ux.vnet.ibm.com,
        peterz@...radead.org, akpm@...ux-foundation.org,
        kirill@...temov.name, ak@...ux.intel.com, mhocko@...nel.org,
        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>,
        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,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org
Subject: Re: [v5,22/22] powerpc/mm: Add speculative page fault

On (11/02/17 15:11), Laurent Dufour wrote:
> On 26/10/2017 10:14, kemi wrote:
> > Some regression is found by LKP-tools(linux kernel performance) on this patch series
> > tested on Intel 2s/4s Skylake platform. 
> > The regression result is sorted by the metric will-it-scale.per_process_ops.
> 
> Hi Kemi,
> 
> Thanks for reporting this, I'll try to address it by turning some features
> of the SPF path off when the process is monothreaded.

make them madvice()-able?
not all multi-threaded apps will necessarily benefit of SPF. right?
just an idea.

	-ss