Am 29.06.2012 13:49, schrieb Mark Nelson:
I'll try to replicate your findings in house. I've got some other things I have to do today, but hopefully I can take a look next week. If I recall correctly, in the other thread you said that sequential writes are using much less CPU time on your systems?
Random 4k writes: 10% idle Seq 4k writes: !! 99,7% !! idle Seq 4M writes: 90% idle > Do you see better scaling in that case? 3 osd nodes: 1 VM: Rand 4k writes: 7000 iops Seq 4k writes: 19900 iops 2 VMs: Rand 4k writes: 6000 iops each Seq 4k writes: 4000 iops each VM 1 Seq 4k writes: 18500 iops each VM 2 4 osd nodes: 1 VM: Rand 4k writes: 14400 iops Seq 4k writes: 19000 iops 2 VMs: Rand 4k writes: 7000 iops each Seq 4k writes: 18000 iops each
To figure out where CPU is being used, you could try various options: oprofile, perf, valgrind, strace. Each has it's own advantages. Here's how you can create a simple callgraph with perf: http://lwn.net/Articles/340010/
10s perf data output while doing random 4k writes: https://raw.github.com/gist/2c16136faebec381ae35/09e6de68a5461a198430a9ec19dfd5392f276706/gistfile1.txt Stefan -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
