Stealing From Smart People
So my previous post showed a trick with stuffing extra bits into the pointers of a simple hash table. In most real situations, we want the hash to still be useful as the number of elements increases: the simple hash I used will slow down dramatically as we pass 75% utilization. In addition, we want …
Continue reading “More Realistic Hashing: Cache Sensitivity Part II”
(FIXED: my “NoMatched” bench was bogus, and actually the same as “Matched” case. Graphs changed, but conclusions the same.) Everyone loves hash tables; certainly the networking code in the kernel uses them heavily and I do too. But with more work on TDB (which is basically a hash table in a file), I’ve been re-measuring …
Continue reading “Hash Tables: In A Cache-Sensitive World? (FIXED)”
Several months ago Donna Benjamin convinced me to speak at LUV, and now the time is approaching. My intent is to give a talk about bits and pieces, and rely on questions to see what the audience is interested in. Pretty casual and should be heaps of fun if you’re nearby. I will also be …
Continue reading “Linux Users of Victoria: Tuesday 6th April”
Mikael noted in my previous post that Con Kolivas’s lrzip is another interesting compressor. In fact, Con has already done a simple 64-bit enhance of rzip for lrzip, and on our example file it gets 56M vs 55M for xz (lrzip in raw mode, followed by xz, gives 100k worse than just using lrzip: lrzip …
As the kernel archive debates replacing .bz2 files with .xz, I took a brief glance at xz. My test was to take a tarball of the linux kernel source (made from a recent git tree, but excluding the .git directory): linux.2.6.tar 395M For a comparison, bzip2 -9, rzip -9 (which uses bzip2 after finding distant …
libreplace is the SAMBA library (also used in ctdb) to provide working implementations of various standard(ish) functions on platforms where they are missing or flawed. It was initially created in 1996 by Andrew Tridgell based on various existing replacement hacks in utils.c (see commit 3ee9d454). The basic format of replace.h is: #ifndef HAVE_STRDUP #define strdup …
I decided that every day I would review some code in ctdb. I never spend enough time reading code, and yet it’s the only way to really get to know a project. And I decided to start easy: with the popt library in ctdb. popt is the command-line parsing library included with the RPM source, …
After slightly disastrous preparation (my left knee in a brace as detailed for the perversely-curious here) my week went well. I tried to get back to my hotel room early each evening to rest as per doctor’s orders (and managed it except Friday night), but polishing my Friday talk tended to take a few hours …
Mikey blogs about linux-next workload with pretty graphs. Ideally, we should all have our patches marshalled before the freeze, and there should be no pre-merge-window peak. I’ve gotten close to this in recent times, by being lazy and being content to wait for the next cycle if I miss one. Rushing things in tends to …
I will freely admit that kernel work has dropped in my priority list. But that didn’t excuse sloppy work like my ae1b22f6e46 commit which sought to sidestep an issue for lguest without me having to do much work. There’s a 64 bit atomic exchange instruction on x86 called cmpxchg8b. This isn’t supported on pre-586 processors, …