Re: Examining the VM splay tree effectiveness

From: Andre Oppermann <andre_at_freebsd.org>
Date: Thu, 30 Sep 2010 23:44:13 +0200
On 30.09.2010 20:04, Roman Divacky wrote:
> On Thu, Sep 30, 2010 at 07:49:00PM +0200, Roman Divacky wrote:
>> On Thu, Sep 30, 2010 at 07:46:32PM +0200, Andre Oppermann wrote:
>>> On 30.09.2010 19:24, Roman Divacky wrote:
>>>> are you aware of Summer of Code 2008 project by Mayur Shardul?
>>>
>>> I remember that there was this project but I never saw any numbers
>>> or other outcome of it.  Haven't checked p4 to look at the code
>>> though.
>>
>> there's a little something:
>>
>> 	http://wiki.freebsd.org/MayurShardul/VM_Algorithm_Improvement
>
> and the actual patch + userspace implementation + benchmarking suite
> is here:
>
> http://code.google.com/p/google-summer-of-code-2008-freebsd/downloads/detail?name=Mayur_Shardul.tar.gz&can=2&q=
>
> it looks like a solid work with solid results to me

I just took a look (not in-depth though) at the patch and can't follow
your conclusion. It is not ready to go into svn in its current state.

Even though it is called a radix trie it doesn't look like one.  On first
impression it looks much more like an AA tree.  A radix trie, which we
already have in our network routing table code, is a variable length
(mask) tree that does path compression.  See net/radix.[ch] and
  http://en.wikipedia.org/wiki/Radix_tree

Extrapolating in a complete guesstimating way from the lookup function
I'd say it may perform only slightly better in an ideal case than a RB
tree but with the added overall expense of requiring external memory to
store the index and branch nodes.  This is probably a nasty disadvantage.

-- 
Andre
Received on Thu Sep 30 2010 - 19:44:15 UTC

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