Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755330AbZJ3FXA (ORCPT ); Fri, 30 Oct 2009 01:23:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755259AbZJ3FW6 (ORCPT ); Fri, 30 Oct 2009 01:22:58 -0400 Received: from e28smtp04.in.ibm.com ([59.145.155.4]:49259 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755243AbZJ3FW5 (ORCPT ); Fri, 30 Oct 2009 01:22:57 -0400 Subject: [PATCH v5 2/4] pSeries: Add hooks to put the CPU into an appropriate offline state To: Nathan Fontenot , Benjamin Herrenschmidt From: Gautham R Shenoy Cc: Peter Zijlstra , Balbir Singh , linux-kernel@vger.kernel.org, Dipankar Sarma , Arun R Bharadwaj , Andrew Morton , Vaidyanathan Srinivasan , linuxppc-dev@lists.ozlabs.org, Ingo Molnar Date: Fri, 30 Oct 2009 10:52:53 +0530 Message-ID: <20091030052253.25493.65063.stgit@sofia.in.ibm.com> In-Reply-To: <20091030052106.25493.42109.stgit@sofia.in.ibm.com> References: <20091030052106.25493.42109.stgit@sofia.in.ibm.com> User-Agent: StGit/0.14.3.384.g9ab0 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 12223 Lines: 391 When a CPU is offlined on POWER currently, we call rtas_stop_self() and hand the CPU back to the resource pool. This path is used for DLPAR which will cause a change in the LPAR configuration which will be visible outside. This patch changes the default state a CPU is put into when it is offlined. On platforms which support ceding the processor to the hypervisor with latency hint specifier value, during a cpu offline operation, instead of calling rtas_stop_self(), we cede the vCPU to the hypervisor while passing a latency hint specifier value. The Hypervisor can use this hint to provide better energy savings. Also, during the offline operation, the control of the vCPU remains with the LPAR as oppposed to returning it to the resource pool. The patch achieves this by creating an infrastructure to set the preferred_offline_state() which can be either - CPU_STATE_OFFLINE: which is the current behaviour of calling rtas_stop_self() - CPU_STATE_INACTIVE: which cedes the vCPU to the hypervisor with the latency hint specifier. The codepath which wants to perform a DLPAR operation can set the preferred_offline_state() of a CPU to CPU_STATE_OFFLINE before invoking cpu_down(). The patch also provides a boot-time command line argument to disable/enable CPU_STATE_INACTIVE. Signed-off-by: Gautham R Shenoy Signed-off-by: Nathan Fontenot --- Documentation/cpu-hotplug.txt | 6 + arch/powerpc/platforms/pseries/hotplug-cpu.c | 182 ++++++++++++++++++++++- arch/powerpc/platforms/pseries/offline_states.h | 18 ++ arch/powerpc/platforms/pseries/smp.c | 19 ++ 4 files changed, 216 insertions(+), 9 deletions(-) create mode 100644 arch/powerpc/platforms/pseries/offline_states.h diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index 9d620c1..4d4a644 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -49,6 +49,12 @@ maxcpus=n Restrict boot time cpus to n. Say if you have 4 cpus, using additional_cpus=n (*) Use this to limit hotpluggable cpus. This option sets cpu_possible_map = cpu_present_map + additional_cpus +cede_offline={"off","on"} Use this option to disable/enable putting offlined + processors to an extended H_CEDE state on + supported pseries platforms. + If nothing is specified, + cede_offline is set to "on". + (*) Option valid only for following architectures - ia64 diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c index ebff6d9..6ea4698 100644 --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c @@ -30,6 +30,7 @@ #include #include "xics.h" #include "plpar_wrappers.h" +#include "offline_states.h" /* This version can't take the spinlock, because it never returns */ static struct rtas_args rtas_stop_self_args = { @@ -39,6 +40,55 @@ static struct rtas_args rtas_stop_self_args = { .rets = &rtas_stop_self_args.args[0], }; +static DEFINE_PER_CPU(enum cpu_state_vals, preferred_offline_state) = + CPU_STATE_OFFLINE; +static DEFINE_PER_CPU(enum cpu_state_vals, current_state) = CPU_STATE_OFFLINE; + +static enum cpu_state_vals default_offline_state = CPU_STATE_OFFLINE; + +static int cede_offline_enabled __read_mostly = 1; + +/* + * Enable/disable cede_offline when available. + */ +static int __init setup_cede_offline(char *str) +{ + if (!strcmp(str, "off")) + cede_offline_enabled = 0; + else if (!strcmp(str, "on")) + cede_offline_enabled = 1; + else + return 0; + return 1; +} + +__setup("cede_offline=", setup_cede_offline); + +enum cpu_state_vals get_cpu_current_state(int cpu) +{ + return per_cpu(current_state, cpu); +} + +void set_cpu_current_state(int cpu, enum cpu_state_vals state) +{ + per_cpu(current_state, cpu) = state; +} + +enum cpu_state_vals get_preferred_offline_state(int cpu) +{ + return per_cpu(preferred_offline_state, cpu); +} + +void set_preferred_offline_state(int cpu, enum cpu_state_vals state) +{ + per_cpu(preferred_offline_state, cpu) = state; +} + +void set_default_offline_state(int cpu) +{ + per_cpu(preferred_offline_state, cpu) = default_offline_state; +} + static void rtas_stop_self(void) { struct rtas_args *args = &rtas_stop_self_args; @@ -56,11 +106,61 @@ static void rtas_stop_self(void) static void pseries_mach_cpu_die(void) { + unsigned int cpu = smp_processor_id(); + unsigned int hwcpu = hard_smp_processor_id(); + u8 cede_latency_hint = 0; + local_irq_disable(); idle_task_exit(); xics_teardown_cpu(); - unregister_slb_shadow(hard_smp_processor_id(), __pa(get_slb_shadow())); - rtas_stop_self(); + + if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) { + set_cpu_current_state(cpu, CPU_STATE_INACTIVE); + cede_latency_hint = 2; + + get_lppaca()->idle = 1; + if (!get_lppaca()->shared_proc) + get_lppaca()->donate_dedicated_cpu = 1; + + printk(KERN_INFO + "cpu %u (hwid %u) ceding for offline with hint %d\n", + cpu, hwcpu, cede_latency_hint); + while (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) { + extended_cede_processor(cede_latency_hint); + printk(KERN_INFO "cpu %u (hwid %u) returned from cede.\n", + cpu, hwcpu); + printk(KERN_INFO + "Decrementer value = %x Timebase value = %llx\n", + get_dec(), get_tb()); + } + + printk(KERN_INFO "cpu %u (hwid %u) got prodded to go online\n", + cpu, hwcpu); + + if (!get_lppaca()->shared_proc) + get_lppaca()->donate_dedicated_cpu = 0; + get_lppaca()->idle = 0; + } + + if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) { + unregister_slb_shadow(hwcpu, __pa(get_slb_shadow())); + + /* + * NOTE: Calling start_secondary() here for now to + * start new context. + * However, need to do it cleanly by resetting the + * stack pointer. + */ + start_secondary(); + + } else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) { + + set_cpu_current_state(cpu, CPU_STATE_OFFLINE); + unregister_slb_shadow(hard_smp_processor_id(), + __pa(get_slb_shadow())); + rtas_stop_self(); + } + /* Should never get here... */ BUG(); for(;;); @@ -106,18 +206,43 @@ static int pseries_cpu_disable(void) return 0; } +/* + * pseries_cpu_die: Wait for the cpu to die. + * @cpu: logical processor id of the CPU whose death we're awaiting. + * + * This function is called from the context of the thread which is performing + * the cpu-offline. Here we wait for long enough to allow the cpu in question + * to self-destroy so that the cpu-offline thread can send the CPU_DEAD + * notifications. + * + * OTOH, pseries_mach_cpu_die() is called by the @cpu when it wants to + * self-destruct. + */ static void pseries_cpu_die(unsigned int cpu) { int tries; - int cpu_status; + int cpu_status = 1; unsigned int pcpu = get_hard_smp_processor_id(cpu); - for (tries = 0; tries < 25; tries++) { - cpu_status = query_cpu_stopped(pcpu); - if (cpu_status == 0 || cpu_status == -1) - break; - cpu_relax(); + if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) { + cpu_status = 1; + for (tries = 0; tries < 1000; tries++) { + if (get_cpu_current_state(cpu) == CPU_STATE_INACTIVE) { + cpu_status = 0; + break; + } + cpu_relax(); + } + } else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) { + + for (tries = 0; tries < 25; tries++) { + cpu_status = query_cpu_stopped(pcpu); + if (cpu_status == 0 || cpu_status == -1) + break; + cpu_relax(); + } } + if (cpu_status != 0) { printk("Querying DEAD? cpu %i (%i) shows %i\n", cpu, pcpu, cpu_status); @@ -252,10 +377,41 @@ static struct notifier_block pseries_smp_nb = { .notifier_call = pseries_smp_notifier, }; +#define MAX_CEDE_LATENCY_LEVELS 4 +#define CEDE_LATENCY_PARAM_LENGTH 10 +#define CEDE_LATENCY_PARAM_MAX_LENGTH \ + (MAX_CEDE_LATENCY_LEVELS * CEDE_LATENCY_PARAM_LENGTH * sizeof(char)) +#define CEDE_LATENCY_TOKEN 45 + +static char cede_parameters[CEDE_LATENCY_PARAM_MAX_LENGTH]; + +static int parse_cede_parameters(void) +{ + int call_status; + + memset(cede_parameters, 0, CEDE_LATENCY_PARAM_MAX_LENGTH); + call_status = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1, + NULL, + CEDE_LATENCY_TOKEN, + __pa(cede_parameters), + CEDE_LATENCY_PARAM_MAX_LENGTH); + + if (call_status != 0) + printk(KERN_INFO "CEDE_LATENCY: \ + %s %s Error calling get-system-parameter(0x%x)\n", + __FILE__, __func__, call_status); + else + printk(KERN_INFO "CEDE_LATENCY: \ + get-system-parameter successful.\n"); + + return call_status; +} + static int __init pseries_cpu_hotplug_init(void) { struct device_node *np; const char *typep; + int cpu; for_each_node_by_name(np, "interrupt-controller") { typep = of_get_property(np, "compatible", NULL); @@ -283,8 +439,16 @@ static int __init pseries_cpu_hotplug_init(void) smp_ops->cpu_die = pseries_cpu_die; /* Processors can be added/removed only on LPAR */ - if (firmware_has_feature(FW_FEATURE_LPAR)) + if (firmware_has_feature(FW_FEATURE_LPAR)) { pSeries_reconfig_notifier_register(&pseries_smp_nb); + cpu_maps_update_begin(); + if (cede_offline_enabled && parse_cede_parameters() == 0) { + default_offline_state = CPU_STATE_INACTIVE; + for_each_online_cpu(cpu) + set_default_offline_state(cpu); + } + cpu_maps_update_done(); + } return 0; } diff --git a/arch/powerpc/platforms/pseries/offline_states.h b/arch/powerpc/platforms/pseries/offline_states.h new file mode 100644 index 0000000..22574e0 --- /dev/null +++ b/arch/powerpc/platforms/pseries/offline_states.h @@ -0,0 +1,18 @@ +#ifndef _OFFLINE_STATES_H_ +#define _OFFLINE_STATES_H_ + +/* Cpu offline states go here */ +enum cpu_state_vals { + CPU_STATE_OFFLINE, + CPU_STATE_INACTIVE, + CPU_STATE_ONLINE, + CPU_MAX_OFFLINE_STATES +}; + +extern enum cpu_state_vals get_cpu_current_state(int cpu); +extern void set_cpu_current_state(int cpu, enum cpu_state_vals state); +extern enum cpu_state_vals get_preferred_offline_state(int cpu); +extern void set_preferred_offline_state(int cpu, enum cpu_state_vals state); +extern void set_default_offline_state(int cpu); +extern int start_secondary(void); +#endif diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c index 440000c..8868c01 100644 --- a/arch/powerpc/platforms/pseries/smp.c +++ b/arch/powerpc/platforms/pseries/smp.c @@ -48,6 +48,7 @@ #include "plpar_wrappers.h" #include "pseries.h" #include "xics.h" +#include "offline_states.h" /* @@ -84,6 +85,9 @@ static inline int __devinit smp_startup_cpu(unsigned int lcpu) /* Fixup atomic count: it exited inside IRQ handler. */ task_thread_info(paca[lcpu].__current)->preempt_count = 0; + if (get_cpu_current_state(lcpu) == CPU_STATE_INACTIVE) + goto out; + /* * If the RTAS start-cpu token does not exist then presume the * cpu is already spinning. @@ -98,6 +102,7 @@ static inline int __devinit smp_startup_cpu(unsigned int lcpu) return 0; } +out: return 1; } @@ -111,12 +116,16 @@ static void __devinit smp_xics_setup_cpu(int cpu) vpa_init(cpu); cpu_clear(cpu, of_spin_map); + set_cpu_current_state(cpu, CPU_STATE_ONLINE); + set_default_offline_state(cpu); } #endif /* CONFIG_XICS */ static void __devinit smp_pSeries_kick_cpu(int nr) { + long rc; + unsigned long hcpuid; BUG_ON(nr < 0 || nr >= NR_CPUS); if (!smp_startup_cpu(nr)) @@ -128,6 +137,16 @@ static void __devinit smp_pSeries_kick_cpu(int nr) * the processor will continue on to secondary_start */ paca[nr].cpu_start = 1; + + set_preferred_offline_state(nr, CPU_STATE_ONLINE); + + if (get_cpu_current_state(nr) == CPU_STATE_INACTIVE) { + hcpuid = get_hard_smp_processor_id(nr); + rc = plpar_hcall_norets(H_PROD, hcpuid); + if (rc != H_SUCCESS) + panic("Error: Prod to wake up processor %d Ret= %ld\n", + nr, rc); + } } static int smp_pSeries_cpu_bootable(unsigned int nr) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/