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Re: Propose Release Goals (delayed ;) - xz compression


On Wed, 2013-10-16 at 17:32:37 +0100, David Goodenough wrote:
> xy may only use a tiny bit, but the combination of apt-get, dpkg and
> xy seems to cause problems.  Its not just BeagleBones, there are x86
> machines with just 64MB still on sale.

Ok, I went through the dpkg code, and have reduced a bit its memory
usage (and line count too!), which will get included in 1.17.2.

First, when loading the .list files, dpkg was slurping them into a
non-freeing memory pool, and populating the file list structures from
that, the problem is that all the shared files and directories were
left allocated on the heap; now the code just allocates the paths that
are non-duped.

And second, for *each* non-shared file on the system it was wasting 9
pointers, which is pretty significant, more so when taking into account
64-bit pointers.

For example on one of my 64-bit systems, with 220481 paths installed, I
go from 62.8 MiB to 46.1 MiB max resident memory, a saving of 16.7 MiB.
That should compensate a bit for the slight increase in memory usage
from xz.


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