[[ANNOUNCE] 3.6.4-rt11] On 31/10/2012 (Wed 02:19) Thomas Gleixner wrote: > Dear RT Folks, > > I'm pleased to announce the 3.6.4-rt11 release.
The rt11 content is present on master in the 3.6-rt patch repo: http://git.kernel.org/?p=linux/kernel/git/paulg/3.6-rt-patches.git I've also created a v3.6.4-rt11-fixes branch, which contains a fix for the preempt-lazy TIF test on x86_32 (please check this; I really should not be left unattended, mucking around in .S files while on vacation). It is queued in the series right after the preempt-lazy-support.patch. There is also a trivial fix to remove a needless whitespace change (also appeared in preempt-lazy-support.patch) that triggers a git nag during a "git am" of it. Passes quick boot test on x86_32 UP (Note: I didn't try booting without the TIF %cl patch; not sure what would have happened there...) [ quick link to TIF patch @kernel.org: http://goo.gl/7Gbtg ] Paul. -- > > Changes since 3.6.3-rt10: > > * Crypto wreckage fix (Milan Broz) > > Another proof why copy and paste should be forbidden, but if that > would happen most of us would be serving time. > > * Another attempt to tame SLUB > > My previous approach turned out to be too naive though this one > has at least held up against massive memory stress tests. It's a > very simple and straight forward aproach now and while I'm quite > sure that it will not fall over as it did before, there might be > hidden latency issues with that new version. > > So please give it a proper testing! > > * Lazy preemption > > It has become an obsession to mitigate the determinism > vs. throughput loss of RT. Looking at the mainline semantics of > preemption points gives a hint why RT sucks throughput wise for > ordinary SCHED_OTHER tasks. One major issue is the wakeup of > tasks which are right away preempting the waking task while the > waking task holds a lock on which the woken task will block right > after having preempted the wakee. In mainline this is prevented > due to the implicit preemption disable of spin/rw_lock held > regions. On RT this is not possible due to the fully preemptible > nature of sleeping spinlocks. > > Though for a SCHED_OTHER task preempting another SCHED_OTHER task > this is really not a correctness issue. RT folks are concerned > about SCHED_FIFO/RR tasks preemption and not about the purely > fairness driven SCHED_OTHER preemption latencies. > > So I introduced a lazy preemption mechanism which only applies to > SCHED_OTHER tasks preempting another SCHED_OTHER task. Aside of > the existing preempt_count each tasks sports now a > preempt_lazy_count which is manipulated on lock acquiry and > release. This is slightly incorrect as for lazyness reasons I > coupled this on migrate_disable/enable so some other mechanisms > get the same treatment (e.g. get_cpu_light). > > Now on the scheduler side instead of setting NEED_RESCHED this > sets NEED_RESCHED_LAZY in case of a SCHED_OTHER/SCHED_OTHER > preemption and therefor allows to exit the waking task the lock > held region before the woken task preempts. That also works > better for cross CPU wakeups as the other side can stay in the > adaptive spinning loop. > > For RT class preemption there is no change. This simply sets > NEED_RESCHED and forgoes the lazy preemption counter. > > Initial test do not expose any observable latency increasement, > but history shows that I've been proven wrong before :) > > The lazy preemption mode is per default on, but with > CONFIG_SCHED_DEBUG enabled it can be disabled via: > > # echo NO_PREEMPT_LAZY >/sys/kernel/debug/sched_features > > and reenabled via > > # echo PREEMPT_LAZY >/sys/kernel/debug/sched_features > > The test results so far are very machine and workload dependent, > but there is a clear trend that it enhances the non RT workload > performance. > > Please give it a try and share your experience! > > Known issues: > > There is still some "softirq pending xx" fallout which I have > not been able to investigate yet, but that's on my top priority > list. It's not a critical issue and only annoys people with > CONFIG_NO_HZ=y configurations. > > > The delta patch against 3.6.4-rt10 is appended below and can be found > here: > > > http://www.kernel.org/pub/linux/kernel/projects/rt/3.6/incr/patch-3.6.4-rt10-rt11.patch.xz > > > The RT patch against 3.6.4 can be found here: > > > http://www.kernel.org/pub/linux/kernel/projects/rt/3.6/patch-3.6.4-rt11.patch.xz > > The split quilt queue is available at: > > > http://www.kernel.org/pub/linux/kernel/projects/rt/3.6/patches-3.6.4-rt11.tar.xz > > Enjoy, > > tglx > > -------------> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
