diff options
Diffstat (limited to 'kernel/sched/loadavg.c')
| -rw-r--r-- | kernel/sched/loadavg.c | 34 |
1 files changed, 15 insertions, 19 deletions
diff --git a/kernel/sched/loadavg.c b/kernel/sched/loadavg.c index 89a989e4d758..a171c1258109 100644 --- a/kernel/sched/loadavg.c +++ b/kernel/sched/loadavg.c @@ -6,10 +6,6 @@ * figure. Its a silly number but people think its important. We go through * great pains to make it work on big machines and tickless kernels. */ - -#include <linux/export.h> -#include <linux/sched/loadavg.h> - #include "sched.h" /* @@ -32,29 +28,29 @@ * Due to a number of reasons the above turns in the mess below: * * - for_each_possible_cpu() is prohibitively expensive on machines with - * serious number of cpus, therefore we need to take a distributed approach + * serious number of CPUs, therefore we need to take a distributed approach * to calculating nr_active. * * \Sum_i x_i(t) = \Sum_i x_i(t) - x_i(t_0) | x_i(t_0) := 0 * = \Sum_i { \Sum_j=1 x_i(t_j) - x_i(t_j-1) } * * So assuming nr_active := 0 when we start out -- true per definition, we - * can simply take per-cpu deltas and fold those into a global accumulate + * can simply take per-CPU deltas and fold those into a global accumulate * to obtain the same result. See calc_load_fold_active(). * - * Furthermore, in order to avoid synchronizing all per-cpu delta folding + * Furthermore, in order to avoid synchronizing all per-CPU delta folding * across the machine, we assume 10 ticks is sufficient time for every - * cpu to have completed this task. + * CPU to have completed this task. * * This places an upper-bound on the IRQ-off latency of the machine. Then * again, being late doesn't loose the delta, just wrecks the sample. * - * - cpu_rq()->nr_uninterruptible isn't accurately tracked per-cpu because - * this would add another cross-cpu cacheline miss and atomic operation - * to the wakeup path. Instead we increment on whatever cpu the task ran - * when it went into uninterruptible state and decrement on whatever cpu + * - cpu_rq()->nr_uninterruptible isn't accurately tracked per-CPU because + * this would add another cross-CPU cacheline miss and atomic operation + * to the wakeup path. Instead we increment on whatever CPU the task ran + * when it went into uninterruptible state and decrement on whatever CPU * did the wakeup. This means that only the sum of nr_uninterruptible over - * all cpus yields the correct result. + * all CPUs yields the correct result. * * This covers the NO_HZ=n code, for extra head-aches, see the comment below. */ @@ -115,11 +111,11 @@ calc_load(unsigned long load, unsigned long exp, unsigned long active) * Handle NO_HZ for the global load-average. * * Since the above described distributed algorithm to compute the global - * load-average relies on per-cpu sampling from the tick, it is affected by + * load-average relies on per-CPU sampling from the tick, it is affected by * NO_HZ. * * The basic idea is to fold the nr_active delta into a global NO_HZ-delta upon - * entering NO_HZ state such that we can include this as an 'extra' cpu delta + * entering NO_HZ state such that we can include this as an 'extra' CPU delta * when we read the global state. * * Obviously reality has to ruin such a delightfully simple scheme: @@ -146,9 +142,9 @@ calc_load(unsigned long load, unsigned long exp, unsigned long active) * busy state. * * This is solved by pushing the window forward, and thus skipping the - * sample, for this cpu (effectively using the NO_HZ-delta for this cpu which + * sample, for this CPU (effectively using the NO_HZ-delta for this CPU which * was in effect at the time the window opened). This also solves the issue - * of having to deal with a cpu having been in NO_HZ for multiple LOAD_FREQ + * of having to deal with a CPU having been in NO_HZ for multiple LOAD_FREQ * intervals. * * When making the ILB scale, we should try to pull this in as well. @@ -299,7 +295,7 @@ calc_load_n(unsigned long load, unsigned long exp, } /* - * NO_HZ can leave us missing all per-cpu ticks calling + * NO_HZ can leave us missing all per-CPU ticks calling * calc_load_fold_active(), but since a NO_HZ CPU folds its delta into * calc_load_nohz per calc_load_nohz_start(), all we need to do is fold * in the pending NO_HZ delta if our NO_HZ period crossed a load cycle boundary. @@ -363,7 +359,7 @@ void calc_global_load(unsigned long ticks) return; /* - * Fold the 'old' NO_HZ-delta to include all NO_HZ cpus. + * Fold the 'old' NO_HZ-delta to include all NO_HZ CPUs. */ delta = calc_load_nohz_fold(); if (delta) |