Fix the long term ULE load balancer so that it actually works. The
initial call to sched_balance() during startup is meant to initialize balance_ticks, but does not actually do that since smp_started is still zero at that time. Since balance_ticks does not get set, there are no further calls to sched_balance(). Fix this by setting balance_ticks in sched_initticks() since we know the value of balance_interval at that time, and eliminate the useless startup call to sched_balance(). We don't need to randomize the intial value of balance_ticks. Since there is now only one call to sched_balance(), we can hoist the tests at the top of this function out to the caller and avoid the overhead of the function call when running a SMP kernel on UP hardware. PR: 223914 Reviewed by: kib MFC after: 2 weeks
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@ -884,9 +884,6 @@ sched_balance(void)
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{
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struct tdq *tdq;
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if (smp_started == 0 || rebalance == 0)
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return;
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balance_ticks = max(balance_interval / 2, 1) +
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(sched_random() % balance_interval);
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tdq = TDQ_SELF();
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@ -1413,7 +1410,6 @@ sched_setup_smp(void)
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panic("Can't find cpu group for %d\n", i);
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}
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balance_tdq = TDQ_SELF();
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sched_balance();
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}
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#endif
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@ -1474,6 +1470,7 @@ sched_initticks(void *dummy)
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* what realstathz is.
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*/
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balance_interval = realstathz;
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balance_ticks = balance_interval;
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affinity = SCHED_AFFINITY_DEFAULT;
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#endif
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if (sched_idlespinthresh < 0)
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@ -2382,7 +2379,7 @@ sched_clock(struct thread *td)
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/*
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* We run the long term load balancer infrequently on the first cpu.
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*/
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if (balance_tdq == tdq) {
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if (balance_tdq == tdq && smp_started != 0 && rebalance != 0) {
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if (balance_ticks && --balance_ticks == 0)
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sched_balance();
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}
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