Hi!
> @@ -192,6 +192,26 @@ config RCU_TRACE
> Say Y/M here if you want to enable RCU tracing in-kernel/module.
> Say N if you are unsure.
>
> +config ADAPTIVE_RTLOCK
> + bool "Adaptive real-time locks"
> + default y
tabs vs. spaces.
> + If unsure, say Y
Missing dot?
> @@ -7,6 +7,7 @@
> * Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <[EMAIL
> PROTECTED]>
> * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt
> * Copyright (C) 2006 Esben Nielsen
> + * Copyright (C) 2008 Novell, Inc.
It would be nice to list some names, too.
> --- /dev/null
> +++ b/kernel/rtmutex_adaptive.h
> @@ -0,0 +1,134 @@
> +/*
> + * Adaptive RT lock support
> + *
> + * There are pros and cons when deciding between the two basic forms of
> + * locking primitives (spinning vs sleeping). Without going into great
> + * detail on either one, we note that spinlocks have the advantage of
> + * lower overhead for short hold locks. However, they also have a
> + * con in that they create indeterminate latencies since preemption
> + * must traditionally be disabled while the lock is held (to prevent
> deadlock).
> + *
> + * We want to avoid non-deterministic critical sections in -rt. Therefore,
> + * when realtime is enabled, most contexts are converted to threads, and
> + * likewise most spinlock_ts are converted to sleepable rt-mutex derived
> + * locks. This allows the holder of the lock to remain fully preemptible,
> + * thus reducing a major source of latencies in the kernel.
> + *
> + * However, converting what was once a true spinlock into a sleeping lock
> + * may also decrease performance since the locks will now sleep under
> + * contention. Since the fundamental lock used to be a spinlock, it is
> + * highly likely that it was used in a short-hold path and that release
> + * is imminent. Therefore sleeping only serves to cause context-thrashing.
> + *
> + * Adaptive RT locks use a hybrid approach to solve the problem. They
> + * spin when possible, and sleep when necessary (to avoid deadlock, etc).
> + * This significantly improves many areas of the performance of the -rt
> + * kernel.
> + *
> + * Copyright (C) 2008 Novell, Inc.,
> + * Sven Dietrich, Peter Morreale, and Gregory Haskins
GPL?
> +/*
> + * Adaptive-rtlocks will busywait when possible, and sleep only if
> + * necessary. Note that the busyloop looks racy, and it is....but we do
> + * not care. If we lose any races it simply means that we spin one more
> + * time before seeing that we need to break-out on the next iteration.
> + *
> + * We realize this is a relatively large function to inline, but note that
> + * it is only instantiated 1 or 2 times max, and it makes a measurable
> + * performance different to avoid the call.
> + *
> + * Returns 1 if we should sleep
> + *
> + */
Kerneldoc?
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
