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SubjectRe: BFS cpu scheduler v0.304 stable release
On Fri, 2009-10-16 at 21:58 +1100, Con Kolivas wrote:
> A lot of people have been wanting to know when BFS, the Brain Fuck Scheduler
> had reached a stable version, so as requested, I'm announcing the first known
> stable release of the Brain Fuck Scheduler, version 0.304. The goals and
> purpose of this patch should be well known by now. It is aimed at end users
> and for comparison purposes, though constructive developer input is welcome.

I've taken BFS out for a few spins while looking into BFS vs CFS latency
reports, and noticed a couple problems I'll share, comparison testing
has been healthy for CFS, so maybe BFS can profit as well. Below are
some bfs304 vs my working tree numbers from a run this morning, looking
to see if some issues seen in earlier releases were still present.

Comments on noted issues:

It looks like there may be some affinity troubles, and there definitely
seems to be a fairness bug still lurking. No idea what's up with that,
but see data below, it's pretty nasty. Any sleepy load competing with a
pure hog seems to be troublesome.

The pgsql+oltp test data is very interesting to me, pgsql+oltp hates
preemption with a passion, because of it's USERLAND spinlocks. Preempt
the lock holder, and watch the fun. Your preemption model suits it very
well at the low end, and does pretty well all the way though. Really
interesting to me is the difference in 1 and 2 client throughput, why
I'm including these.

msql+oltp and tbench look like they're griping about affinity to me, but
I haven't instrumented anything, so can't be sure. mysql+oltp I know is
a wakeup preemption and is very affinity sensitive. Too little wakeup
preemption, it suffers, any load balancing, it suffers.

What vmark is so upset about, I have no idea. I know it's very affinity
sensitive, and hates wakeup preemption passionately.


tip 108841 messages per second
tip++ 116260 messages per second
31.bfs304 28279 messages per second

tbench 8
tip 938.421 MB/sec 8 procs
tip++ 952.302 MB/sec 8 procs
31.bfs304 709.121 MB/sec 8 procs

clients 1 2 4 8 16 32 64 128 256
tip 9999.36 18493.54 34652.91 34253.13 32057.64 30297.43 28300.96 25450.14 20675.99
tip++ 10041.16 18531.16 34934.22 34192.65 32829.65 32010.55 30341.31 27340.65 22724.87
31.bfs304 9459.85 14952.44 32209.07 29724.03 28608.02 27051.10 24851.44 21223.15 15809.46

clients 1 2 4 8 16 32 64 128 256
tip 13577.63 26510.67 51871.05 51374.62 50190.69 45494.64 37173.83 27767.09 22795.23
tip++ 13685.69 26693.42 52056.45 51733.30 50854.75 49790.95 48972.02 47517.34 44999.22
31.bfs304 15467.03 21126.57 52673.76 50972.41 49652.54 46015.73 44567.18 40419.90 33276.67

fairness bug in 31.bfs304?

set CPU governor to performance first, as in all benchmarking.
taskset -c 0 pert (100% CPU hog TSC perturbation measurement proggy)
taskset -p 0x1 `pidof Xorg`

perf stat taskset -c 0 konsole -e exit
31.bfs304 2.073724549 seconds time elapsed
tip++ 0.989323860 seconds time elapsed

note: amarok pins itself to CPU0, and is set up to use mysql database.

prep: cache warmup run.
perf stat amarokapp (quit after 12000 song mp3 collection is loaded)

31.bfs304 136.418518486 seconds time elapsed
tip++ 19.439268066 seconds time elapsed

prep: restart amarok, wait for load, start playing

perf stat taskset -c 0 mplayer -nosound 3DMark2000.mkv (exact 6 minute movie)
31.bfs304 432.712500554 seconds time elapsed
tip++ 363.622519583 seconds time elapsed

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