On Tue, May 15, 2012 at 10:46:39AM -0700, Greg KH wrote: > On Tue, May 15, 2012 at 09:34:51AM -0400, Matthew Wilcox wrote: > > What we'd really like is for people to think about how they might use > > fast NVM inside the kernel. There's likely to be a lot of it (at least in > > servers); all the technologies are promising cheaper per-bit prices than > > DRAM, so it's likely to be sold in larger capacities than DRAM is today. > > > > Caching is one obvious use (be it FS-Cache, Bcache, Flashcache or > > something else), but I bet there are more radical things we can do > > with it. What if we stored the inode cache in it? Would booting with > > a hot inode cache improve boot times? How about storing the tree of > > 'struct devices' in it so we don't have to rescan the busses at startup? > > Rescanning the busses at startup are required anyway, as devices can be > added and removed when the power is off, and I would be amazed if that > is actually taking any measurable time. Do you have any numbers for > this for different busses? Hi Greg, I wasn't particularly serious about this example ... I did once time the scan of a PCIe bus and it took a noticable number of milliseconds (which is why we now only scan the first device for the downstream "bus" of root ports and downstream ports). I'm just trying to stimulate a bit of discussion of possible usages for persistent memory. > What about pramfs for the nvram? I have a recent copy of the patches, > and I think they are clean enough for acceptance, there was no > complaints the last time it was suggested. Can you use that for this > type of hardware? pramfs is definitely one filesystem that's under investigation. I know there will be types of NVM for which it won't be suitable, so rather than people calling pramfs-specific functions, the notion is to get a core API in the VFS that can call into the various different filesystems that can handle the vagaries of different types of NVM. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
