Messages in this thread Patch in this message | | | Date | Tue, 07 May 2013 13:43:52 +0800 | From | Alex Shi <> | Subject | Re: [PATCH v5 7/7] sched: consider runnable load average in effective_load |
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On 05/06/2013 05:59 PM, Preeti U Murthy wrote: > Suggestion1: Would change the CPU share calculation to use runnable load > average all the time. > > Suggestion2: Did opposite of point 2 above,it used runnable load average > while calculating the CPU share *before* a new task has been woken up > while it retaining the instantaneous weight to calculate the CPU share > after a new task could be woken up. > > So since there was no uniformity in the calculation of CPU shares in > approaches 2 and 3, I think it caused a regression. However I still > don't understand how approach 4-Suggestion2 made that go away although > there was non-uniformity in the CPU shares calculation. > > But as Paul says we could retain the usage of instantaneous loads > wherever there is calculation of CPU shares for the reason he mentioned > and leave effective_load() and calc_cfs_shares() untouched. > > This also brings forth another question,should we modify wake_affine() > to pass the runnable load average of the waking up task to effective_load(). > > What do you think?
I am not Paul. :)
The acceptable patch of pgbench attached. In fact, since effective_load is mixed with direct load and tg's runnable load. the patch looks no much sense. So, I am going to agree to drop it if there is no performance benefit on my benchmarks.
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From f58519a8de3cebb7a865c9911c00dce5f1dd87f2 Mon Sep 17 00:00:00 2001 From: Alex Shi <alex.shi@intel.com> Date: Fri, 3 May 2013 13:29:04 +0800 Subject: [PATCH 7/7] sched: consider runnable load average in effective_load
effective_load calculates the load change as seen from the root_task_group. It needs to engage the runnable average of changed task.
Thanks for Morten Rasmussen and PeterZ's reminder of this.
Signed-off-by: Alex Shi <alex.shi@intel.com> --- kernel/sched/fair.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index ca0e051..b683909 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2980,15 +2980,15 @@ static void task_waking_fair(struct task_struct *p) #ifdef CONFIG_FAIR_GROUP_SCHED /* - * effective_load() calculates the load change as seen from the root_task_group + * effective_load() calculates load avg change as seen from the root_task_group * * Adding load to a group doesn't make a group heavier, but can cause movement * of group shares between cpus. Assuming the shares were perfectly aligned one * can calculate the shift in shares. * - * Calculate the effective load difference if @wl is added (subtracted) to @tg - * on this @cpu and results in a total addition (subtraction) of @wg to the - * total group weight. + * Calculate the effective load avg difference if @wl is added (subtracted) to + * @tg on this @cpu and results in a total addition (subtraction) of @wg to the + * total group load avg. * * Given a runqueue weight distribution (rw_i) we can compute a shares * distribution (s_i) using: @@ -3002,7 +3002,7 @@ static void task_waking_fair(struct task_struct *p) * rw_i = { 2, 4, 1, 0 } * s_i = { 2/7, 4/7, 1/7, 0 } * - * As per wake_affine() we're interested in the load of two CPUs (the CPU the + * As per wake_affine() we're interested in load avg of two CPUs (the CPU the * task used to run on and the CPU the waker is running on), we need to * compute the effect of waking a task on either CPU and, in case of a sync * wakeup, compute the effect of the current task going to sleep. @@ -3012,20 +3012,20 @@ static void task_waking_fair(struct task_struct *p) * * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2) * - * Suppose we're interested in CPUs 0 and 1, and want to compute the load + * Suppose we're interested in CPUs 0 and 1, and want to compute the load avg * differences in waking a task to CPU 0. The additional task changes the * weight and shares distributions like: * * rw'_i = { 3, 4, 1, 0 } * s'_i = { 3/8, 4/8, 1/8, 0 } * - * We can then compute the difference in effective weight by using: + * We can then compute the difference in effective load avg by using: * * dw_i = S * (s'_i - s_i) (3) * * Where 'S' is the group weight as seen by its parent. * - * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7) + * Therefore the effective change in load avg on CPU 0 would be 5/56 (3/8 - 2/7) * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 - * 4/7) times the weight of the group. */ @@ -3070,7 +3070,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg) /* * wl = dw_i = S * (s'_i - s_i); see (3) */ - wl -= se->load.weight; + wl -= se->avg.load_avg_contrib; /* * Recursively apply this logic to all parent groups to compute @@ -3116,14 +3116,14 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) */ if (sync) { tg = task_group(current); - weight = current->se.load.weight; + weight = current->se.avg.load_avg_contrib; this_load += effective_load(tg, this_cpu, -weight, -weight); load += effective_load(tg, prev_cpu, 0, -weight); } tg = task_group(p); - weight = p->se.load.weight; + weight = p->se.avg.load_avg_contrib; /* * In low-load situations, where prev_cpu is idle and this_cpu is idle -- 1.7.12 -- Thanks Alex
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