On Mon, Sep 28, 2020 at 05:28:57PM +0200, Jan Kratochvil wrote:
On Mon, 28 Sep 2020 12:31:59 +0200, Mark Wielaard wrote:
> I do find your statistics per package useful because they show dwz is
> in general effective by producing at least 20% (more) on-disk size
I am ignoring the on-disk size, I always measure just *-debuginfo.rpm size.
If anyone is concerned about on-disk size then Fedora should have already
enabled zlib section compression which would reduce the on-disk *.debug size
by 52.84% for the whole distro. Or even implement zstd section compression
probably with even bigger size decrease (and even lower performance hit
already low enough).
I was just discussing that recently with the Hotspot Perf GUI
maintainer. And we concluded that if .debug files would be compressed
then we would need an uncompressed cache somewhere. The issue with
having the on-disk debuginfo files compressed is that for
debugger/tracing/profiling tools it incurs an significant
decompression time delay and extra memory usage. Especially for a
profiling tool that only needs to quickly get a little information it
is much more convenient to be able to simply mmap the .debug file,
check the aranges and directly jump to the correct DIE offset. See
So why do you mention the on-disk size now?
Because I believe it is the most important benchmark. The on-disk size
is not just the installed file size, but it is also the in memory size
of the data structures that need to be stored and parsed. So a 20%
smaller on-disk size also (roughly) means 20% less DIEs and abbrevs
that need to be parsed or held into memory.