From ad5d1c888e556bc00c4e86f452cad4a3a87d22c1 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Sun, 20 Mar 2011 15:28:03 +0000 Subject: powerpc: Fix accounting of softirq time when idle commit cf9efce0ce31 (powerpc: Account time using timebase rather than PURR) used in_irq() to detect if the time was spent in interrupt processing. This only catches hardirq context so if we are in softirq context and in the idle loop we end up accounting it as idle time. If we instead use in_interrupt() we catch both softirq and hardirq time. The issue was found when running a network intensive workload. top showed the following: 0.0%us, 1.1%sy, 0.0%ni, 85.7%id, 0.0%wa, 9.9%hi, 3.3%si, 0.0%st 85.7% idle. But this was wildly different to the perf events data. To confirm the suspicion I ran something to keep the core busy: # yes > /dev/null & 8.2%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 10.3%hi, 81.4%si, 0.0%st We only got 8.2% of the CPU for the userspace task and softirq has shot up to 81.4%. With the patch below top shows the correct stats: 0.0%us, 0.0%sy, 0.0%ni, 5.3%id, 0.0%wa, 13.3%hi, 81.3%si, 0.0%st Signed-off-by: Anton Blanchard Cc: stable@kernel.org Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/time.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/powerpc/kernel/time.c') diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 09d31dbf43f9..aa9269600ca2 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -356,7 +356,7 @@ void account_system_vtime(struct task_struct *tsk) } get_paca()->user_time_scaled += user_scaled; - if (in_irq() || idle_task(smp_processor_id()) != tsk) { + if (in_interrupt() || idle_task(smp_processor_id()) != tsk) { account_system_time(tsk, 0, delta, sys_scaled); if (stolen) account_steal_time(stolen); -- cgit v1.2.3 From 963e5d3b76d657f1ebcf3561446d2ba1872bbfa2 Mon Sep 17 00:00:00 2001 From: Benjamin Herrenschmidt Date: Tue, 29 Mar 2011 14:51:10 +1100 Subject: powerpc: Make decrementer interrupt robust against offlined CPUs With some implementations, it is possible that a timer interrupt occurs every few seconds on an offline CPU. In this case, just re-arm the decrementer and return immediately Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/time.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) (limited to 'arch/powerpc/kernel/time.c') diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index aa9269600ca2..375480c56eb9 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -577,14 +577,21 @@ void timer_interrupt(struct pt_regs * regs) struct clock_event_device *evt = &decrementer->event; u64 now; + /* Ensure a positive value is written to the decrementer, or else + * some CPUs will continue to take decrementer exceptions. + */ + set_dec(DECREMENTER_MAX); + + /* Some implementations of hotplug will get timer interrupts while + * offline, just ignore these + */ + if (!cpu_online(smp_processor_id())) + return; + trace_timer_interrupt_entry(regs); __get_cpu_var(irq_stat).timer_irqs++; - /* Ensure a positive value is written to the decrementer, or else - * some CPUs will continuue to take decrementer exceptions */ - set_dec(DECREMENTER_MAX); - #if defined(CONFIG_PPC32) && defined(CONFIG_PMAC) if (atomic_read(&ppc_n_lost_interrupts) != 0) do_IRQ(regs); -- cgit v1.2.3 From 84ffae55af79d7b8834fd0c08d0d1ebf2c77f91e Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Thu, 7 Apr 2011 21:44:21 +0000 Subject: powerpc: Fix oops if scan_dispatch_log is called too early We currently enable interrupts before the dispatch log for the boot cpu is setup. If a timer interrupt comes in early enough we oops in scan_dispatch_log: Unable to handle kernel paging request for data at address 0x00000010 ... .scan_dispatch_log+0xb0/0x170 .account_system_vtime+0xa0/0x220 .irq_enter+0x88/0xc0 .do_IRQ+0x48/0x230 The patch below adds a check to scan_dispatch_log to ensure the dispatch log has been allocated. Signed-off-by: Anton Blanchard Cc: Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/time.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/powerpc/kernel/time.c') diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 375480c56eb9..f33acfd872ad 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -229,6 +229,9 @@ static u64 scan_dispatch_log(u64 stop_tb) u64 stolen = 0; u64 dtb; + if (!dtl) + return 0; + if (i == vpa->dtl_idx) return 0; while (i < vpa->dtl_idx) { -- cgit v1.2.3