Date: Sun, 12 Feb 2012 12:58:34 +0100
From: Andrea Righi <andrea@betterlinux.com>
To: Hillf Danton <dhillf@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Minchan Kim <minchan.kim@gmail.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Johannes Weiner <jweiner@redhat.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: Re: [RFC] [PATCH v5 0/3] fadvise: support POSIX_FADV_NOREUSE
Message-ID: <20120212115834.GA1548@thinkpad>
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On Sun, Feb 12, 2012 at 03:16:07PM +0800, Hillf Danton wrote:
> Hello Andrea
> 
> On Sun, Feb 12, 2012 at 8:21 AM, Andrea Righi <andrea@betterlinux.com> wrote:
> [...]
> > ?- Some of the routines to implement the generic interval tree has been taken
> > ? from the x86 PAT code, that uses interval trees to keep track of PAT ranges
> > ? (in the future it would be interesting to convert also the x86 PAT code to
> > ? use the generic interval tree implementation).
> >
> Perhaps the tree implemented in this work could also be used in tracking
> regions in mm/hugetlb.c.
> 
> Thanks
> Hillf

Thanks, Hillf.

Yes, I quickly looked at the hugtlb code, it seems another potential
user of the interval tree. Now all the hugetlb regions are stored in a
list, the interval tree is a more efficient structure for lookups -
O(log(n)), so there are probably advantages in presence of many
different disjoint intervals.

mmh... at the moment there's not a way to map region_count() with the
current kinterval API, but we can easily extend it to provide also this
feature (count the overlap size of two intervals).

-Andrea
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