Messages in this thread Patch in this message | | | From | Diwakar Tundlam <> | Date | Mon, 30 Jan 2012 10:14:23 -0800 | Subject | Fix bug: Scheduler's idle-load-balancer not running in first 5 mins after bootup |
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We ran into this at Nvidia. QA filed a bug saying coremark_4pthreads scores lower (as if running on 3 cores) when run shortly after bootup. But later its score increases to expected values on 4 cores.
This patch is relevant to linux-2.6.39 but I noticed this fix is not made in linux-3.0, 3.1, 3.2 or 3.3 also.
Please see commit log for more details of the problem and fix.
Thanks, Diwakar. Tegra Android Kernel SW Engg. NVIDIA. Santa Clara, CA
commit d04d7ef0e3f8c70bd6cd5abb2abc0236aa8d1f7c Author: Diwakar Tundlam <dtundlam@nvidia.com> Date: Wed Jan 18 18:58:57 2012 -0800
scheduler: domain: init next_balance in nohz_idle_balancer with jiffies
The next_balance parameter of nohz_idle_balancer should be initialized to jiffies since jiffies itself is initialized to 300 seconds shy of overflow. Otherwise, nohz_idle_balancer does not run for the first 5 mins after bootup.
Signed-off-by: Diwakar Tundlam <dtundlam@nvidia.com> Reviewed-by: Aleksandr Frid <afrid@nvidia.com> Reviewed-by: Peter Boonstoppel <pboonstoppel@nvidia.com> Reviewed-by: Satya Popuri <spopuri@nvidia.com>
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c index c5b09f7..506c5da 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -8288,6 +8288,7 @@ void __init sched_init(void) atomic_set(&nohz.load_balancer, nr_cpu_ids); atomic_set(&nohz.first_pick_cpu, nr_cpu_ids); atomic_set(&nohz.second_pick_cpu, nr_cpu_ids); + nohz.next_balance = jiffies; #endif /* May be allocated at isolcpus cmdline parse time */ if (cpu_isolated_map == NULL)
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