[9fans] fossil+venti performance question
Hello, fans. I’m running Plan 9(labs) on public QEMU/KVM service. My Plan 9 system has a slow read performance problem. I ran 'iostats md5sum /386/9pcf’, DMA is on, read result is 150KB/s. but write performance is fast. My Plan 9 system has a 200GB HDD, formatted with fossil+venti. disk layout is: - 9fat 100MB - nvram 512B - fossil31.82GB - arenas159.11GB - isect 7.95GB - bloom 512MB - swap 512MB Also, I explained other installations. 1)200GB HDD with fossil only. 2)100GB HDD with fossil+venti. Read performance is fast (about 15MB/s) both installations. Could you tell me the reason?
Re: [9fans] fossil+venti performance question
The reason, in general: In a fossil+venti setup, fossil runs (basically) as a cache for venti. If your access just hits fossil, it’ll be quick; if not, you hit the (significantly slower) venti. I bet if you re-run the same test twice in a row, you’re going to see dramatically improved performance. Try it. If that’s true, the question is really one of venti performance; if not, you may have another system config issue. There are various changes you can make to how venti uses disk/memory that can speed things up, but I don’t have a good handle on which to suggest first. Your write performance in that test isn’t really relevant: they’re not hitting the file system at all. I’m not sure why you’d see a difference in a fossil+venti setup of a different size, but the partition size relationships, and the in-memory cache size relationships, are what’s mostly important. a
Re: [9fans] fossil+venti performance question
I'm experiencing the same issue as well. When I launch vacfs on the same machine as Venti, reading is very slow. When I launch vacfs on another Plan 9 or Unix machine, reading is fast. I've just made some measurements when reading a file: Vacfs running on the same machine as Venti: 151 KB/s Vacfs running on another machine: 5131 KB/s -- David du Colombier
