[Buildroot] [PATCH 4/4] pkg-download: check hasahes for locally cached files

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Dear Peter Korsgaard,

On Tue, 02 Dec 2014 10:27:05 +0100, Peter Korsgaard wrote:

>  > So in essence, from now on, at each build, we are re-checking the
>  > hashes, while previously they were checked only when the file was
>  > downloaded. Not that great for build time, but well, again maybe the
>  > time to check the hashes is negligible compared to the build time. And
>  > we can assume that a big tarball, which takes a certain time to hash,
>  > will also contain a lot of source code to build, so the time to
>  > calculate the hash is proportional to the build time of the package. So
>  > if you're ready to spend several minutes to build Qt, you're probably
>  > ready to wait a few more seconds to calculate the hash of the Qt
>  > tarball each time.
> 
> I doubt it adds any significant time. Probably the hash and extract
> steps are largely I/O bound, so "pre-heating" the page cache by
> calculating a hash on the tarball before extracting it shouldn't matter
> much.

True. Anyway, my comment really wasn't rejecting the idea, just
pointing out the additional stuff we are doing.

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com