linux-kernel - Re: [RFC] [PATCH v5 0/3] fadvise: support POSIX_FADV

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Message-ID: <87sjigx7ho.fsf@linux.vnet.ibm.com>
Date:	Sun, 12 Feb 2012 23:24:27 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Andrea Righi <andrea@...terlinux.com>,
	Hillf Danton <dhillf@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Johannes Weiner <jweiner@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] [PATCH v5 0/3] fadvise: support POSIX_FADV_NOREUSE

On Sun, 12 Feb 2012 12:58:34 +0100, Andrea Righi <andrea@...terlinux.com> wrote:
> 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@...terlinux.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).
> 

I am also extending the hugetlb region list in the hugetlb cgroup
patchset i recently posted to make sure we don't merge region if the
associated private data doesn't match (in my case it is the pointer to
hugetlb cgroup). Ref:
http://article.gmane.org/gmane.linux.kernel.mm/73829

The goal is to make sure a region add with different private value
results in below.


    old
      |       hcg1      |
      -------------------

new
|             hcg2               |
----------------------------------

results in 

 | hcg2   | |     hcg1       | |   hcg2 |
 ---------  __________________ ----------


-aneesh

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