From 478735e38887077ac77a9756121b6ce0cb956e2f Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Wed, 27 Oct 2010 15:34:15 -0700 Subject: /proc/stat: fix scalability of irq sum of all cpu In /proc/stat, the number of per-IRQ event is shown by making a sum each irq's events on all cpus. But we can make use of kstat_irqs(). kstat_irqs() do the same calculation, If !CONFIG_GENERIC_HARDIRQ, it's not a big cost. (Both of the number of cpus and irqs are small.) If a system is very big and CONFIG_GENERIC_HARDIRQ, it does for_each_irq() for_each_cpu() - look up a radix tree - read desc->irq_stat[cpu] This seems not efficient. This patch adds kstat_irqs() for CONFIG_GENRIC_HARDIRQ and change the calculation as for_each_irq() look up radix tree for_each_cpu() - read desc->irq_stat[cpu] This reduces cost. A test on (4096cpusp, 256 nodes, 4592 irqs) host (by Jack Steiner) %time cat /proc/stat > /dev/null Before Patch: 2.459 sec After Patch : .561 sec [akpm@linux-foundation.org: unexport kstat_irqs, coding-style tweaks] [akpm@linux-foundation.org: fix unused variable 'per_irq_sum'] Signed-off-by: KAMEZAWA Hiroyuki Tested-by: Jack Steiner Acked-by: Jack Steiner Cc: Yinghai Lu Cc: Ingo Molnar Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/irq/irqdesc.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'kernel/irq/irqdesc.c') diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c index 9d917ff72675..9988d03797f5 100644 --- a/kernel/irq/irqdesc.c +++ b/kernel/irq/irqdesc.c @@ -393,3 +393,18 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu) struct irq_desc *desc = irq_to_desc(irq); return desc ? desc->kstat_irqs[cpu] : 0; } + +#ifdef CONFIG_GENERIC_HARDIRQS +unsigned int kstat_irqs(unsigned int irq) +{ + struct irq_desc *desc = irq_to_desc(irq); + int cpu; + int sum = 0; + + if (!desc) + return 0; + for_each_possible_cpu(cpu) + sum += desc->kstat_irqs[cpu]; + return sum; +} +#endif /* CONFIG_GENERIC_HARDIRQS */ -- cgit v1.2.2