From: Suresh Siddha Date: Thu, 23 Aug 2007 13:18:02 +0000 (+0200) Subject: sched: skip updating rq's next_balance under null SD X-Git-Tag: v2.6.23-rc4~24^2~1 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=f549da848eca595abca14ebc5e1bf00fd72aa53d;p=linux.git sched: skip updating rq's next_balance under null SD Was playing with sched_smt_power_savings/sched_mc_power_savings and found out that while the scheduler domains are reconstructed when sysfs settings change, rebalance_domains() can get triggered with null domain on other cpus, which is setting next_balance to jiffies + 60*HZ. Resulting in no idle/busy balancing for 60 seconds. Fix this. Signed-off-by: Suresh Siddha Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched.c b/kernel/sched.c index d96030db8ff7..a4b22d93e00d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3043,6 +3043,7 @@ static inline void rebalance_domains(int cpu, enum cpu_idle_type idle) struct sched_domain *sd; /* Earliest time when we have to do rebalance again */ unsigned long next_balance = jiffies + 60*HZ; + int update_next_balance = 0; for_each_domain(cpu, sd) { if (!(sd->flags & SD_LOAD_BALANCE)) @@ -3079,8 +3080,10 @@ static inline void rebalance_domains(int cpu, enum cpu_idle_type idle) if (sd->flags & SD_SERIALIZE) spin_unlock(&balancing); out: - if (time_after(next_balance, sd->last_balance + interval)) + if (time_after(next_balance, sd->last_balance + interval)) { next_balance = sd->last_balance + interval; + update_next_balance = 1; + } /* * Stop the load balance at this level. There is another @@ -3090,7 +3093,14 @@ static inline void rebalance_domains(int cpu, enum cpu_idle_type idle) if (!balance) break; } - rq->next_balance = next_balance; + + /* + * next_balance will be updated only when there is a need. + * When the cpu is attached to null domain for ex, it will not be + * updated. + */ + if (likely(update_next_balance)) + rq->next_balance = next_balance; } /*