Messages in this thread Patch in this message | | | Date | Thu, 21 Oct 2010 16:03:43 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [PATCH v2 2/2] try to fix /proc/stat scalability of irq sum of all cpu |
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From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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
Changelog: - rebased onto mmotm-1020 (kernel/irq/handle.c is modified)
Tested-by: Jack Steiner <steiner@sgi.com> Acked-by: Jack Steiner <steiner@sgi.com> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- fs/proc/stat.c | 9 ++------- include/linux/kernel_stat.h | 4 ++++ kernel/irq/irqdesc.c | 16 ++++++++++++++++ 3 files changed, 22 insertions(+), 7 deletions(-)
Index: mmotm-1020/fs/proc/stat.c =================================================================== --- mmotm-1020.orig/fs/proc/stat.c +++ mmotm-1020/fs/proc/stat.c @@ -108,13 +108,8 @@ static int show_stat(struct seq_file *p, seq_printf(p, "intr %llu", (unsigned long long)sum); /* sum again ? it could be updated? */ - for_each_irq_nr(j) { - per_irq_sum = 0; - for_each_possible_cpu(i) - per_irq_sum += kstat_irqs_cpu(j, i); - - seq_printf(p, " %u", per_irq_sum); - } + for_each_irq_nr(j) + seq_printf(p, " %u", kstat_irqs(j)); seq_printf(p, "\nctxt %llu\n" Index: mmotm-1020/include/linux/kernel_stat.h =================================================================== --- mmotm-1020.orig/include/linux/kernel_stat.h +++ mmotm-1020/include/linux/kernel_stat.h @@ -86,6 +86,7 @@ static inline unsigned int kstat_softirq /* * Number of interrupts per specific IRQ source, since bootup */ +#ifndef CONFIG_GENERIC_HARDIRQS static inline unsigned int kstat_irqs(unsigned int irq) { unsigned int sum = 0; @@ -96,6 +97,9 @@ static inline unsigned int kstat_irqs(un return sum; } +#else +extern unsigned int kstat_irqs(unsigned int irq); +#endif /* * Number of interrupts per cpu, since bootup Index: mmotm-1020/kernel/irq/irqdesc.c =================================================================== --- mmotm-1020.orig/kernel/irq/irqdesc.c +++ mmotm-1020/kernel/irq/irqdesc.c @@ -393,3 +393,19 @@ unsigned int kstat_irqs_cpu(unsigned int 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; +} +EXPORT_SYMBOL_GPL(kstat_irqs); +#endif /*CONFIG_GENERIC_HARDIRQS*/
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