On Wed, Jun 25, 2014 at 02:09:34PM +0200, Koen Kooi wrote: > > Op 25 jun. 2014, om 10:59 heeft Lennart Poettering <[email protected]> > het volgende geschreven: > > > On Wed, 25.06.14 07:28, Zbigniew Jędrzejewski-Szmek ([email protected]) > > wrote: > > > >> Hi, > >> a POC patch to compress coredumps after they are written. In my simple > >> tests, this brings huge savings, because the compressed coredump can > >> compress to ~5%. > >> > >> Unfortunately the core is first written uncompressed, then compressed > >> by reading from disk and writing to the output file. This is ugly and > >> slow, but I don't see a way around, if we want to get the backtrace > >> without keeping everything in memory. > > > > I have the suspicion that there indeed is no other nice way for > > this... Hence looks good to me. > > > >> 'coredumpctl gdb' is not implemented yet (the decompression part is > >> missing). > > > > Hmm, we probably should add a coredump.conf option for this to turn on. > > > > Hmm, thinking about this, another idea might be to simply let the fs > > solve this by adding a high-level coredump.conf option to turn on > > FS_COMPR_FL for the coredump. This should do the right thing on btrfs > > (afaics at least), but of course would leave other file systems out. But > > then again, we develop the OS for tomorrow, not for yesterday here... > > > > But then again, maybe this stuff shouldn't be exclusive. Maybe a new > > coredump.conf option Compress=(filesystem|file|no) or so? (and maybe > > even Compress=auto, which does the right thing automatically, depending > > if the fs supports compression) After all, doing both file-level and > > filesystem-level compression makes little sense... > > The way btrfs currently does compression is to compress every (iirc 4k) block > separately. Compressing the whole file at once will give a much bigger > saving, especially when using xz. So btrfs/lzo will give you ~50% compression > ratio vs the 5% mentioned above, a huge difference. I don't know how reiser4 > or zfs tackle this.
In the light of this, I skipped the filesystem compression part. I implemented the rest and pushed. Zbyszek _______________________________________________ systemd-devel mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/systemd-devel
