[Buildroot] [PATCH 4/4] pkg-download: check hasahes for locally cached files
Peter Korsgaard
peter at korsgaard.com
Tue Dec 2 09:27:05 UTC 2014
>>>>> "Thomas" == Thomas Petazzoni <thomas.petazzoni at free-electrons.com> writes:
Hi,
>> So, to avoid this situation, check the hashes prior to doing the
>> download. If the hashes match, consider the locally cached file genuine,
>> and do not download it. However, if the locally cached file does not
>> match the known hashes we have for it, it is promptly removed, and a
>> download is re-attempted.
> 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.
--
Bye, Peter Korsgaard
More information about the buildroot
mailing list