[Buildroot] [PATCH 4/4] pkg-download: check hasahes for locally cached files
Thomas Petazzoni
thomas.petazzoni at free-electrons.com
Tue Dec 2 09:30:21 UTC 2014
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
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