Re: [Tracker] PATCH: Faster PNG extractor

[Martyn Russell <martyn lanedo com>]

On 27/06/13 16:08, Jonatan Pålsson wrote:
> On 27 June 2013 16:48, Aleksander Morgado <aleksander lanedo com
> <mailto:aleksander lanedo com>> wrote:
>
>     On 27/06/13 16:26, Jonatan Pålsson wrote:
>      > To start with, I would like to submit a patch containing a new
>     extractor
>      > for PNG files, which is faster than the original.
>      >
>      > The reason behind the speed increase with this extractor compared
>     to the
>      > old extractor is that the new extractor seek()s out the metadata
>     fields
>      > in the PNG, rather than traverse the entire file to find them, as the
>      > old extractor did (using libpng).
>
>     Could you share some numbers on which is the actual speed improvement?
>     E.g. extracting 1000 random PNGs before took Xs, now it takes Ys.
>
> Certainly!
>
> I'm running Tracker on a PandaBoard Rev A4. 1000 replicated PNGs were
> used, I could make the replicated file available, there is nothing
> special about it.
> I used the following command to measure the running times:
>
> # For png-faster
> tracker-control -r ; echo 3 > /proc/sys/vm/drop_caches ; sync ; sync ;
> time /usr/lib/tracker/tracker-miner-fs -v 0 --no-daemon
>
> # For the original PNG extractor
> tracker-control -r ; /usr/lib/tracker/tracker-extract -m png
> echo 3 > /proc/sys/vm/drop_caches ; sync ; sync ; time
> /usr/lib/tracker/tracker-miner-fs -v 0 --no-daemon
>
> And here are the results:
> # png-faster
> real    0m14.804s
> user    0m4.945s
> sys     0m1.313s
>
> # original
> real    1m33.274s
> user    0m5.250s
> sys     0m1.820s

That's quite some difference!

Thanks for posting some numbers. Important! :)

My first thought is, why did you create a new extractor instead of 
improve the original one?

The patch link you gave is good, but I would love to see a diff from our 
actual extractor right now to see how easily we could merge the changes 
into that one.

--
Regards,
Martyn

Founder and CEO of Lanedo GmbH.