From mboxrd@z Thu Jan 1 00:00:00 1970 From: eric.dumazet@gmail.com (Eric Dumazet) Date: Fri, 10 Dec 2010 18:18:20 +0100 Subject: [BUG] 2.6.37-rc3 massive interactivity regression on ARM In-Reply-To: <1291988866.6803.171.camel@twins> References: <20101208142814.GE9777@n2100.arm.linux.org.uk> <1291851079-27061-1-git-send-email-venki@google.com> <1291899120.29292.7.camel@twins> <1291917330.6803.7.camel@twins> <1291920939.6803.38.camel@twins> <1291936593.13513.3.camel@laptop> <1291975704.6803.59.camel@twins> <1291987065.6803.151.camel@twins> <1291987635.6803.161.camel@twins> <1291988866.6803.171.camel@twins> Message-ID: <1292001500.3580.268.camel@edumazet-laptop> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Le vendredi 10 d?cembre 2010 ? 14:47 +0100, Peter Zijlstra a ?crit : > Full patch.. > unt_system_vtime(struct task_struct *curr) > { > unsigned long flags; > + s64 delta; > int cpu; > - u64 now, delta; > > if (!sched_clock_irqtime) > return; > > local_irq_save(flags); > - > cpu = smp_processor_id(); > - now = sched_clock_cpu(cpu); > - delta = now - per_cpu(irq_start_time, cpu); > - per_cpu(irq_start_time, cpu) = now; > - /* > - * We do not account for softirq time from ksoftirqd here. > - * We want to continue accounting softirq time to ksoftirqd thread > - * in that case, so as not to confuse scheduler with a special task > - * that do not consume any time, but still wants to run. > - */ > + delta = sched_clock_cpu(cpu) - per_cpu(irq_start_time, cpu); > + per_cpu(irq_start_time, cpu) += delta; We should add some checkpatch warning to any new per_cpu() use. delta = sched_clock_cpu(cpu) - __this_cpu_read(irq_start_time); __this_cpu_add(irq_start_time, delta); Also irq_time_write_begin() and irq_time_write_end() could be faster (called for current cpu) static inline void irq_time_write_begin(void) { __this_cpu_inc(irq_time_seq.sequence); smp_wmb(); } static inline void irq_time_write_end(void) { smp_wmb(); __this_cpu_inc(irq_time_seq.sequence); }