diff options
| -rw-r--r-- | include/linux/kernel.h | 18 | ||||
| -rw-r--r-- | kernel/Kconfig.preempt | 57 |
2 files changed, 62 insertions, 13 deletions
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index e25b97062ce..687ba8c9973 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -58,15 +58,23 @@ struct completion; * be biten later when the calling function happens to sleep when it is not * supposed to. */ +#ifdef CONFIG_PREEMPT_VOLUNTARY +extern int cond_resched(void); +# define might_resched() cond_resched() +#else +# define might_resched() do { } while (0) +#endif + #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP -#define might_sleep() __might_sleep(__FILE__, __LINE__) -#define might_sleep_if(cond) do { if (unlikely(cond)) might_sleep(); } while (0) -void __might_sleep(char *file, int line); + void __might_sleep(char *file, int line); +# define might_sleep() \ + do { __might_sleep(__FILE__, __LINE__); might_resched(); } while (0) #else -#define might_sleep() do {} while(0) -#define might_sleep_if(cond) do {} while (0) +# define might_sleep() do { might_resched(); } while (0) #endif +#define might_sleep_if(cond) do { if (unlikely(cond)) might_sleep(); } while (0) + #define abs(x) ({ \ int __x = (x); \ (__x < 0) ? -__x : __x; \ diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index 34c631221aa..0b46a5dff4c 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -1,15 +1,56 @@ -config PREEMPT - bool "Preemptible Kernel" +choice + prompt "Preemption Model" + default PREEMPT_NONE + +config PREEMPT_NONE + bool "No Forced Preemption (Server)" + help + This is the traditional Linux preemption model, geared towards + throughput. It will still provide good latencies most of the + time, but there are no guarantees and occasional longer delays + are possible. + + Select this option if you are building a kernel for a server or + scientific/computation system, or if you want to maximize the + raw processing power of the kernel, irrespective of scheduling + latencies. + +config PREEMPT_VOLUNTARY + bool "Voluntary Kernel Preemption (Desktop)" help - This option reduces the latency of the kernel when reacting to - real-time or interactive events by allowing a low priority process to - be preempted even if it is in kernel mode executing a system call. - This allows applications to run more reliably even when the system is + This option reduces the latency of the kernel by adding more + "explicit preemption points" to the kernel code. These new + preemption points have been selected to reduce the maximum + latency of rescheduling, providing faster application reactions, + at the cost of slighly lower throughput. + + This allows reaction to interactive events by allowing a + low priority process to voluntarily preempt itself even if it + is in kernel mode executing a system call. This allows + applications to run more 'smoothly' even when the system is under load. - Say Y here if you are building a kernel for a desktop, embedded - or real-time system. Say N if you are unsure. + Select this if you are building a kernel for a desktop system. + +config PREEMPT + bool "Preemptible Kernel (Low-Latency Desktop)" + help + This option reduces the latency of the kernel by making + all kernel code (that is not executing in a critical section) + preemptible. This allows reaction to interactive events by + permitting a low priority process to be preempted involuntarily + even if it is in kernel mode executing a system call and would + otherwise not be about to reach a natural preemption point. + This allows applications to run more 'smoothly' even when the + system is under load, at the cost of slighly lower throughput + and a slight runtime overhead to kernel code. + + Select this if you are building a kernel for a desktop or + embedded system with latency requirements in the milliseconds + range. + +endchoice config PREEMPT_BKL bool "Preempt The Big Kernel Lock" |