diff options
Diffstat (limited to 'Documentation/hrtimers.txt')
| -rw-r--r-- | Documentation/hrtimers.txt | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/Documentation/hrtimers.txt b/Documentation/hrtimers.txt index 7620ff735faf..ce31f65e12e7 100644 --- a/Documentation/hrtimers.txt +++ b/Documentation/hrtimers.txt | |||
| @@ -10,7 +10,7 @@ back and forth trying to integrate high-resolution and high-precision | |||
| 10 | features into the existing timer framework, and after testing various | 10 | features into the existing timer framework, and after testing various |
| 11 | such high-resolution timer implementations in practice, we came to the | 11 | such high-resolution timer implementations in practice, we came to the |
| 12 | conclusion that the timer wheel code is fundamentally not suitable for | 12 | conclusion that the timer wheel code is fundamentally not suitable for |
| 13 | such an approach. We initially didnt believe this ('there must be a way | 13 | such an approach. We initially didn't believe this ('there must be a way |
| 14 | to solve this'), and spent a considerable effort trying to integrate | 14 | to solve this'), and spent a considerable effort trying to integrate |
| 15 | things into the timer wheel, but we failed. In hindsight, there are | 15 | things into the timer wheel, but we failed. In hindsight, there are |
| 16 | several reasons why such integration is hard/impossible: | 16 | several reasons why such integration is hard/impossible: |
| @@ -27,7 +27,7 @@ several reasons why such integration is hard/impossible: | |||
| 27 | high-res timers. | 27 | high-res timers. |
| 28 | 28 | ||
| 29 | - the unpredictable [O(N)] overhead of cascading leads to delays which | 29 | - the unpredictable [O(N)] overhead of cascading leads to delays which |
| 30 | necessiate a more complex handling of high resolution timers, which | 30 | necessitate a more complex handling of high resolution timers, which |
| 31 | in turn decreases robustness. Such a design still led to rather large | 31 | in turn decreases robustness. Such a design still led to rather large |
| 32 | timing inaccuracies. Cascading is a fundamental property of the timer | 32 | timing inaccuracies. Cascading is a fundamental property of the timer |
| 33 | wheel concept, it cannot be 'designed out' without unevitably | 33 | wheel concept, it cannot be 'designed out' without unevitably |
| @@ -58,7 +58,7 @@ several reasons why such integration is hard/impossible: | |||
| 58 | The primary users of precision timers are user-space applications that | 58 | The primary users of precision timers are user-space applications that |
| 59 | utilize nanosleep, posix-timers and itimer interfaces. Also, in-kernel | 59 | utilize nanosleep, posix-timers and itimer interfaces. Also, in-kernel |
| 60 | users like drivers and subsystems which require precise timed events | 60 | users like drivers and subsystems which require precise timed events |
| 61 | (e.g. multimedia) can benefit from the availability of a seperate | 61 | (e.g. multimedia) can benefit from the availability of a separate |
| 62 | high-resolution timer subsystem as well. | 62 | high-resolution timer subsystem as well. |
| 63 | 63 | ||
| 64 | While this subsystem does not offer high-resolution clock sources just | 64 | While this subsystem does not offer high-resolution clock sources just |
| @@ -68,7 +68,7 @@ The increasing demand for realtime and multimedia applications along | |||
| 68 | with other potential users for precise timers gives another reason to | 68 | with other potential users for precise timers gives another reason to |
| 69 | separate the "timeout" and "precise timer" subsystems. | 69 | separate the "timeout" and "precise timer" subsystems. |
| 70 | 70 | ||
| 71 | Another potential benefit is that such a seperation allows even more | 71 | Another potential benefit is that such a separation allows even more |
| 72 | special-purpose optimization of the existing timer wheel for the low | 72 | special-purpose optimization of the existing timer wheel for the low |
| 73 | resolution and low precision use cases - once the precision-sensitive | 73 | resolution and low precision use cases - once the precision-sensitive |
| 74 | APIs are separated from the timer wheel and are migrated over to | 74 | APIs are separated from the timer wheel and are migrated over to |
| @@ -96,8 +96,8 @@ file systems. The rbtree is solely used for time sorted ordering, while | |||
| 96 | a separate list is used to give the expiry code fast access to the | 96 | a separate list is used to give the expiry code fast access to the |
| 97 | queued timers, without having to walk the rbtree. | 97 | queued timers, without having to walk the rbtree. |
| 98 | 98 | ||
| 99 | (This seperate list is also useful for later when we'll introduce | 99 | (This separate list is also useful for later when we'll introduce |
| 100 | high-resolution clocks, where we need seperate pending and expired | 100 | high-resolution clocks, where we need separate pending and expired |
| 101 | queues while keeping the time-order intact.) | 101 | queues while keeping the time-order intact.) |
| 102 | 102 | ||
| 103 | Time-ordered enqueueing is not purely for the purposes of | 103 | Time-ordered enqueueing is not purely for the purposes of |