features into the existing timer framework, and after testing various
such high-resolution timer implementations in practice, we came to the
conclusion that the timer wheel code is fundamentally not suitable for
-such an approach. We initially didnt believe this ('there must be a way
+such an approach. We initially didn't believe this ('there must be a way
to solve this'), and spent a considerable effort trying to integrate
things into the timer wheel, but we failed. In hindsight, there are
several reasons why such integration is hard/impossible:
high-res timers.
- the unpredictable [O(N)] overhead of cascading leads to delays which
- necessiate a more complex handling of high resolution timers, which
+ necessitate a more complex handling of high resolution timers, which
in turn decreases robustness. Such a design still led to rather large
timing inaccuracies. Cascading is a fundamental property of the timer
wheel concept, it cannot be 'designed out' without unevitably
The primary users of precision timers are user-space applications that
utilize nanosleep, posix-timers and itimer interfaces. Also, in-kernel
users like drivers and subsystems which require precise timed events
-(e.g. multimedia) can benefit from the availability of a seperate
+(e.g. multimedia) can benefit from the availability of a separate
high-resolution timer subsystem as well.
While this subsystem does not offer high-resolution clock sources just
with other potential users for precise timers gives another reason to
separate the "timeout" and "precise timer" subsystems.
-Another potential benefit is that such a seperation allows even more
+Another potential benefit is that such a separation allows even more
special-purpose optimization of the existing timer wheel for the low
resolution and low precision use cases - once the precision-sensitive
APIs are separated from the timer wheel and are migrated over to
a separate list is used to give the expiry code fast access to the
queued timers, without having to walk the rbtree.
-(This seperate list is also useful for later when we'll introduce
-high-resolution clocks, where we need seperate pending and expired
+(This separate list is also useful for later when we'll introduce
+high-resolution clocks, where we need separate pending and expired
queues while keeping the time-order intact.)
Time-ordered enqueueing is not purely for the purposes of
git.openpandora.org / pandora-kernel.git / blobdiff