> If multiple compression schemes are implemented how should the user go > about choosing which one they want? Should it be done at kernel time? Or > with the userland tools on a per file basis(maybe zlib is the default > but a user could say I want this directory to be bzip)?
yes, why not... doing that at mounttime like mount -o compress,cscheme=myzip /dev/xyz /mntpoint would be a good start.... > -----Ursprüngliche Nachricht----- > Von: "Lee Trager" <l...@cs.drexel.edu> > Gesendet: 16.12.08 00:07:32 > An: devz...@web.de > CC: linux-btrfs@vger.kernel.org > Betreff: Re: Compressed Filesystem > If multiple compression schemes are implemented how should the user go > about choosing which one they want? Should it be done at kernel time? Or > with the userland tools on a per file basis(maybe zlib is the default > but a user could say I want this directory to be bzip)? > > On Mon, Dec 15, 2008 at 11:14:01PM +0100, devz...@web.de wrote: > > fantastic feature! > > > > i`m curious: can btrfs support more than one compression scheme at the same > > time, i.e. is compression "pluggable" ? > If you look at compression.c, compression.h, and ctree.h you can clearly > see that support for multiple compression scheme was in mind. Implmented > a new one shouldn't be to hard but you probably want to make the current > system a little bit more pluggable and move all the zlib stuff into > zlib.c. > > > > lzo compression coming to my mind, as this is giving real-time compession > > and may even speed up disk access. > > > > compression ratio isn`t too bad, but speed is awesome and doesn`t need as > > much cpu as gzip. > > > In some tests I've run zlib is actually faster then nocompression > because of the lesser amount of data that has to transfer to and from > the disk. It would be instresting to see how bzip works with this to. > > experimental lzo compression in zfs-fuse showed that it could compress > > tarred kernel-source with 2.99x compressratio (where gzip gave 3.41x), so > > maybe lzo is a better algorithm for realtime filesystem compression... > > > > regards > > roland > > > > > > > > From: Chris Mason <chris.mason <at> oracle.com> > > Subject: Re: Compressed Filesystem > > Newsgroups: gmane.comp.file-systems.btrfs > > Date: 2008-10-29 20:08:42 GMT (6 weeks, 5 days, 1 hour and 53 minutes ago) > > > > On Wed, 2008-10-29 at 12:14 -0600, Anthony Roberts wrote: > > > Hi, I have a few questions about this: > > > > > > > Compression is optional and off by default (mount -o compress to enable > > > > it). When enabled, every file is compressed. > > > > > > Do you know what the CPU load is like with this enabled? > > > > Now that I've finally pushed the code out, you can try it ;) One part > > of the implementation I need to revisit is the place in the code where I > > do compression means that most of the time the single threaded pdflush > > is the one compressing. > > > > This doesn't spread the load very well across the cpus. It can be > > fixed, but I wanted to get the code out there. > > > > The decompression does spread across cpus, and I've gotten about 800MB/s > > doing decompress and checksumming on a zero filled compressed file. At > > the time, the disk was reading 14MB/s. > > > > > > > > Do you know whether data can be compressed at a sufficient rate to still > > > saturate the disk on recent-ish AMD/Intel CPUs? > > > > My recentish intel cpu can compress and checksum at about 120MB/s. > > > > > > If no, is the effective pre-compression I/O rate still comparable to the > > > disk without compression? > > > > > > > It depends on your disks... > > > > > I'm pretty sure that won't even matter in many cases (eg you're seeking > > > too much to care, or you're on a VM with lots of cores but congested > > > disks, or you're dealing with media files that it doesn't bother > > > compressing, etc), but I'm curious what sort of overhead this adds. :) > > > > > > Mostly it seems like a good tradeoff, it trades plentiful cores for scarce > > > disk resources. > > > > This varies quite a bit from workload to workload, in some places it'll > > make a big difference, but many workloads are seek bound and not > > bandwidth bound. > > > > -chris > > > > > > ____________________________________________________________________ > > Psssst! Schon vom neuen WEB.DE MultiMessenger geh?rt? > > Der kann`s mit allen: http://www.produkte.web.de/messenger/?did=3123 > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > > the body of a message to majord...@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > _______________________________________________________________________ Sensationsangebot verlängert: WEB.DE FreeDSL - Telefonanschluss + DSL für nur 16,37 Euro/mtl.!* http://dsl.web.de/?ac=OM.AD.AD008K15039B7069a -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
