Dimitri Sivanich noticed that xtime_lock is held write locked across calc_load() which iterates over all online CPUs. That can cause long latencies for xtime_lock readers on large SMP systems. The load average calculation is an rough estimate anyway so there is no real need to protect the readers vs. the update. It's not a problem when the avenrun array is updated while a reader copies the values. Instead of iterating over all online CPUs let the scheduler_tick code update the number of active tasks shortly before the avenrun update happens. The avenrun update itself is handled by the CPU which calls do_timer(). [ Impact: reduce xtime_lock write locked section ] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> |
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acpi | ||
asm-generic | ||
crypto | ||
drm | ||
keys | ||
linux | ||
math-emu | ||
media | ||
mtd | ||
net | ||
pcmcia | ||
rdma | ||
rxrpc | ||
scsi | ||
sound | ||
trace | ||
video | ||
xen | ||
Kbuild |