From: Dan Williams <dan.j.williams@intel.com>
To: "Raslan, KarimAllah" <karahmed@amazon.de>
Cc: Michal Hocko <mhocko@kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@techsingularity.net>,
Vlastimil Babka <vbabka@suse.cz>,
Johannes Weiner <hannes@cmpxchg.org>,
Yaowei Bai <baiyaowei@cmss.chinamobile.com>,
Joe Perches <joe@perches.com>, Tejun Heo <tj@kernel.org>,
"Liguori, Anthony" <aliguori@amazon.com>,
"Schoenherr, Jan H." <jschoenh@amazon.de>
Subject: Re: [PATCH] sparse: Track the boundaries of memory sections for accurate checks
Date: Wed, 14 Sep 2016 15:05:51 -0700 [thread overview]
Message-ID: <CAPcyv4gQZ-=6SdsGc-YafcAUz0WWxtGuh56CPan1xqSkWbd9=A@mail.gmail.com> (raw)
In-Reply-To: <8B91B5C5-4506-40CB-B7F0-0990A37F95AA@amazon.de>
On Wed, Sep 14, 2016 at 2:40 PM, Raslan, KarimAllah <karahmed@amazon.de> wrote:
>
>
> On 6/20/16, 10:23 AM, "Michal Hocko" <mhocko@kernel.org> wrote:
>
> On Sat 18-06-16 12:11:19, KarimAllah Ahmed wrote:
> > When sparse memory model is used an array of memory sections is created to
> > track each block of contiguous physical pages. Each element of this array
> > contains PAGES_PER_SECTION pages. During the creation of this array the actual
> > boundaries of the memory block is lost, so the whole block is either considered
> > as present or not.
> >
> > pfn_valid() in the sparse memory configuration checks which memory sections the
> > pfn belongs to then checks whether it's present or not. This yields sub-optimal
> > results when the available memory doesn't cover the whole memory section,
> > because pfn_valid will return 'true' even for the unavailable pfns at the
> > boundaries of the memory section.
>
> Please be more verbose of _why_ the patch is needed. Why those
> "sub-optimal results" matter?
>
> Does this make sense to you ?
[ channeling my inner akpm ]
What's the user visible effect of this change? What code is getting
tripped up by pfn_valid() being imprecise, and why is changing
pfn_valid() the preferred fix?
next prev parent reply other threads:[~2016-09-14 22:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-18 10:11 [PATCH] sparse: Track the boundaries of memory sections for accurate checks KarimAllah Ahmed
2016-06-20 8:23 ` Michal Hocko
2016-06-21 14:33 ` [PATCH v2] " KarimAllah Ahmed
2016-09-14 21:40 ` [PATCH] " Raslan, KarimAllah
2016-09-14 22:05 ` Dan Williams [this message]
2016-09-14 22:11 ` Raslan, KarimAllah
2016-09-14 22:53 ` Dan Williams
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