From: Minchan Kim <minchan@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
dan.j.williams@intel.com, mgorman@suse.de, vbabka@suse.cz,
kirill.shutemov@linux.intel.com, dave.hansen@linux.intel.com,
hughd@google.com, linux-arch@vger.kernel.org
Subject: [PATCH] mm: disable fault around on emulated access bit architecture
Date: Wed, 18 May 2016 10:42:29 +0900 [thread overview]
Message-ID: <20160518014229.GB21538@bbox> (raw)
On Tue, May 17, 2016 at 03:34:23PM +0300, Kirill A. Shutemov wrote:
> On Mon, May 16, 2016 at 11:56:32PM +0900, Minchan Kim wrote:
> > On Mon, May 16, 2016 at 05:29:00PM +0300, Kirill A. Shutemov wrote:
> > > > Kirill,
> > > > You wanted to test non-HW access bit system and I did.
> > > > What's your opinion?
> > >
> > > Sorry, for late response.
> > >
> > > My patch is incomlete: we need to find a way to not mark pte as old if we
> > > handle page fault for the address the pte represents.
> >
> > I'm sure you can handle it but my point is there wouldn't be a big gain
> > although you can handle it in non-HW access bit system. Okay, let's be
> > more clear because I don't have every non-HW access bit architecture.
> > At least, current mobile workload in ARM which I have wouldn't be huge
> > benefit.
> > I will say one more.
> > I tested the workload on quad-core system and core speed is not so slow
> > compared to recent other mobile phone SoC. Even when I tested the benchmark
> > without pte_mkold, the benefit is within noise because storage is really
> > slow so major fault is dominant factor. So, I decide test storage from eMMC
> > to eSATA. And then finally, I manage to see the a little beneift with
> > fault_around without pte_mkold.
> >
> > However, let's consider side-effect aspect from fault_around.
> >
> > 1. Increase slab shrinking compard to old
> > 2. high level vmpressure compared to old
> >
> > With considering that regressions on my system, it's really not worth to
> > try at the moment.
> > That's why I wanted to disable fault_around as default in non-HW access
> > bit system.
>
> Feel free to post such patch. I guess it's reasonable.
reply other threads:[~2016-05-18 1:42 UTC|newest]
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