> On Monday 16 April 2007, Ingo Molnar wrote:
> >this is the second release of the CFS (Completely Fair Scheduler)
> >patchset, against v2.6.21-rc7:
> >
> >
http://redhat.com/~mingo/cfs-scheduler/sched-cfs-v2.patch
> >
> >i'd like to thank everyone for the tremendous amount of feedback and
> >testing the v1 patch got - i could hardly keep up with just reading the
> >mails! Some of the stuff people addressed i couldnt implement yet, i
> >mostly concentrated on bugs, regressions and debuggability.
> >
> >there's a fair amount of churn:
> >
> > 15 files changed, 456 insertions(+), 241 deletions(-)
> >
> >But it's an encouraging sign that there was no crash bug found in v1,
> >all the bugs were related to scheduling-behavior details. The code was
> >tested on 3 architectures so far: i686, x86_64 and ia64. Most of the
> >code size increase in -v2 is due to debugging helpers, they'll be
> >removed later. (The new /proc/sched_debug file can be used to see the
> >fine details of CFS scheduling.)
> >
> >Changes since -v1:
> >
> > - make nice levels less starvable. (reported by Willy Tarreau)
> >
> > - fixed child-runs first. A /proc/sys/kernel/sched_child_runs_first
> > flag can be used to turn it on/off. (This might fix the Kaffeine bug
> > reported by S.Ça??lar Onur <)
> >
> > - changed SCHED_FAIR back to SCHED_NORMAL (suggested by Con Kolivas)
> >
> > - UP build fix. (reported by Gabriel C)
> >
> > - timer tick micro-optimization (Dmitry Adamushko)
> >
> > - preemption fix: sched_class->check_preempt_curr method to decide
> > whether to preempt after a wakeup (or at a timer tick). (Found via a
> > fairness-test-utility written for CFS by Mike Galbraith)
> >
> > - start forked children with neutral statistics instead of trying to
> > inherit them from the parent: Willy Tarreau reported that this
> > results in better behavior on extreme workloads, and it also
> > simplifies the code quite nicely. Removed sched_exit() and the
> > ->task_exit() methods.
> >
> > - make nice levels independent of the sched_granularity value
> >
> > - new /proc/sched_debug file listing runqueue details and the rbtree
> >
> > - new SCH-* fields in /proc/<NR>/status to see scheduling details
> >
> > - new cpu-hog feature (off by default) and sysctl tunable to set it:
> > /proc/sys/kernel/sched_max_hog_history_ns tunable defaults to
> > 0 (off). Positive values are meant the maximum 'memory' that the
> > scheduler has of CPU hogs.
> >
> > - various code cleanups
> >
> > - added more statistics temporarily: sum_exec_runtime,
> > sum_wait_runtime.
> >
> > - added -CFS-v2 to EXTRAVERSION
> >
> >as usual, any sort of feedback, bugreports, fixes and suggestions are
> >more than welcome,
> >
> > Ingo
>
> This one (v2-rc2) is not a keeper I'm sorry to say, Ingo. v2-rc0 was much
> better. Watching amanda run with htop, kmails composer is being subjected to
> 5 to 10 second pauses, and htop says that gzip -best isn't getting more that
> 15% of the cpu, and the /amandatapes drive is being written to in a regular
> pattern that seems to be the cause of the pauses according to gkrellm, which
> also seems to track the size of the writes, and can show anything from 4.3k
> to 54 megs as being written in one cycle of its screen update.
