[Ocfs2-tools-devel] [PATCH 2/2] looped chain - Break loop in fsck

[Goldwyn Rodrigues]

Hi Tristan,

On Fri, Mar 5, 2010 at 6:58 PM, tristan ye <tristan.ye at oracle.com> wrote:
>
>
> Goldwyn Rodrigues wrote:
>>
>> Hi Tristan,
>>
>> On Fri, Mar 5, 2010 at 9:56 AM, Goldwyn Rodrigues <rgoldwyn at gmail.com>
>> wrote:
>>
>>>
>>> Hi Tristan,
>>>
>>>
>>> On Fri, Mar 5, 2010 at 8:44 AM, tristan ye <tristan.ye at oracle.com> wrote:
>>>
>>>
>>
>> <snip>
>>
>>
>>>>
>>>> Let me know if you have some other suggestions on it.
>>>>
>>
>> On second thoughts, in an un-cached environment, your algorithm would
>> have more number of disk reads as compared to my algorithm. So, a
>> cached environment might be better, but will consume more memory. I am
>> not sure how you would want to handle this efficiently.
>>
>
> Yes, your time complexity of disk reads is O(N), while mine is O(2N), it we
> disgard the cache.

Correction, it will be N(for slow) + 2N (for fast) = 3N

>
> So the problem is 'Your extra collection/comparions' VS 'My extra disk
> reads', the best way I guess is to compare their efficiency  in a real world
> after we drop all buffer and caches. by doing:
>
> 1. echo 3>/proc/sys/vm/drop_caches
>
> 2. time fsck...
>
>
> The winner will be consuming less time.

Theoretically, this will depend on the size of the loop. Not tried it,
so cannot say practically.


>
> Joel, sunil,
>
> How do you think about that issue?
>
>
>> Even, in my algorithm, it can be improvised by collecting the block
>> numbers in the check_chain loop itself, but lets face it... how often
>> do you get a loop in the chain to do this? We don't want to have
>> multiple collections/comparisons for all chains checked.
>>



-- 
Goldwyn