Negative NFS caching

Matt Dillon has added negative caching for NFS, meaning that NFS will now cache failed lookups, not just successful ones. He details the benefits like so:

“This makes a HUGE difference for programs which search nfs directories, such as compilers (the header file search path), make, and a few other utilities. NFS packet traffic can be reduced upwards of 90%. For example, with /usr/src mounted via NFS, building libc a second time without negative caching generates 66000 packets of NFS traffic in each direction, building libc a second time with negative caching enabled generates 9500 packets worth of NFS traffic, in EACH DIRECTION. While it is true that negative lookups are cached on the NFS server, the huge reduction in network traffic and equivalent reduction in synchronous read latencies result in radically reduced overheads across the board for operations which generate a lot of negative hits. A buildworld test with the default 3 second negative caching timeout went from 2265 seconds to 1900 seconds.”

Unixy system benchmarks

Ivan Voras has finished his benchmark of a system running FreeBSD, NetBSD, DragonFly and Linux. DragonFly does quite well, coming unsurprisingly close to the leader – FreeBSD 4.x. The difference would probably be more pronounced on a multiprocessor system, which wasn’t used in these benchmarks.

The right way to cvsup

For those of us from FreeBSDland, the kernel upgrade process is (well, recently) solidified to a number of steps including mergemaster. Matt Dillon noted that the DragonFly upgrading process is thus:

(update via cvsup)
cd /usr/src
make buildworld
make buildkernel KERNCONF=<kernel config file>
make installkernel KERNCONF=<kernel config file>
make installworld
make upgrade

The “make upgrade” step replaces mergemaster, and should be relatively faster. Credit for this goes to Sascha Wildner for asking for clarification on the dragonfly.bugs mailing list.

Getting a kernel crash dump

Matt Dillon posted this little note on how to get a kernel crash dump, which seems a good idea to archive – this may be useful again:

The best way is to get a kernel crash dump. If your swap area (typically ad0s1b) is large enough to accomodoate main memory, then ‘dumpon /dev/ad0s1b’ (and put ‘dumpdev=/dev/ad0s1b’ in your /etc/rc.conf), and then when it crashed and drops into DDB> type ‘panic’ and hit return twice and it should hopefully generate a crash dump.

For the crash dump to be really useful having the kernel.debug for the kernel that you are running is important. kernel.debug is built automatically when you buildkernel, but only the stripped ‘kernel’ version is actually installed. kernel.debug should still be sitting in the kernel build object directory which is usually /usr/obj/usr/src/sys/<KERNELNAME> (if you used ‘buildkernel’ to build your kernel).

Chris Cleans up

Chris Pressey, the newest committer, has been in a cleanup frenzy – he’s had 140 commits already, many of them cleanup of the existing source code. Go Chris!

Build broken

Matt Dillon’s still missing some parts to the PIPE code in last night’s import from FreeBSD 5. Until this is fixed (hopefully by tomorrow) , the codebase will be somewhat unstable.

Now on BSDNews

If you have a login to BSDNews (and you should – it’s free), you can customize your BSDNews page layout to include the news feed from this very site, listed as “DragonFly BSD”! Thanks to Wes Peters and Chris Coleman for setting that up.

In Europe with 16EUR to spare?

Tobias Florek has plush Freds – the dragonfly mascot for DragonFly. He’s in Europe, and it costs 16 Euros plus shipping – mail fred at First come, first serve. If you live on the western side of the Atlantic, shipping costs make it prohibitive, so no luck for U.S. and Canada residents yet. (A U.S. distributor is being worked on.)