Subject: Re: [PATCH v3 7/12] Use stop machine to update cpu maps

From: Benjamin Herrenschmidt <[email-masked]>
Date: Tue, 23 Apr 2013 10:24:48 +1000

On Mon, 2013-04-22 at 13:41 -0500, Nathan Fontenot wrote:
> From: Jesse Larrew <[email-masked]>
> 
> Platform events such as partition migration or the new PRRN firmware
> feature can cause the NUMA characteristics of a CPU to change, and these
> changes will be reflected in the device tree nodes for the affected
> CPUs.
> 
> This patch registers a handler for Open Firmware device tree updates
> and reconfigures the CPU and node maps whenever the associativity
> changes. Currently, this is accomplished by marking the affected CPUs in
> the cpu_associativity_changes_mask and allowing
> arch_update_cpu_topology() to retrieve the new associativity information
> using hcall_vphn().
> 
> Protecting the NUMA cpu maps from concurrent access during an update
> operation will be addressed in a subsequent patch in this series.

I see no more mention of stop_machine() ... is the patch subject stale ?

Cheers,
Ben.

> Signed-off-by: Nathan Fontenot <[email-masked]>
> ---
> 
>  arch/powerpc/include/asm/firmware.h       |    3 
>  arch/powerpc/include/asm/prom.h           |    1 
>  arch/powerpc/mm/numa.c                    |   99 ++++++++++++++++++++++--------
>  arch/powerpc/platforms/pseries/firmware.c |    1 
>  4 files changed, 79 insertions(+), 25 deletions(-)
> 
> Index: powerpc/arch/powerpc/include/asm/prom.h
> ===================================================================
> --- powerpc.orig/arch/powerpc/include/asm/prom.h	2013-04-15 14:03:52.000000000 -0500
> +++ powerpc/arch/powerpc/include/asm/prom.h	2013-04-15 14:04:47.000000000 -0500
> @@ -128,6 +128,7 @@
>  #define OV5_CMO			0x0480	/* Cooperative Memory Overcommitment */
>  #define OV5_XCMO		0x0440	/* Page Coalescing */
>  #define OV5_TYPE1_AFFINITY	0x0580	/* Type 1 NUMA affinity */
> +#define OV5_PRRN		0x0540	/* Platform Resource Reassignment */
>  #define OV5_PFO_HW_RNG		0x0E80	/* PFO Random Number Generator */
>  #define OV5_PFO_HW_842		0x0E40	/* PFO Compression Accelerator */
>  #define OV5_PFO_HW_ENCR		0x0E20	/* PFO Encryption Accelerator */
> Index: powerpc/arch/powerpc/mm/numa.c
> ===================================================================
> --- powerpc.orig/arch/powerpc/mm/numa.c	2013-04-15 14:04:46.000000000 -0500
> +++ powerpc/arch/powerpc/mm/numa.c	2013-04-15 14:06:20.000000000 -0500
> @@ -1257,7 +1257,8 @@
>  static u8 vphn_cpu_change_counts[NR_CPUS][MAX_DISTANCE_REF_POINTS];
>  static cpumask_t cpu_associativity_changes_mask;
>  static int vphn_enabled;
> -static void set_topology_timer(void);
> +static int prrn_enabled;
> +static void reset_topology_timer(void);
>  
>  /*
>   * Store the current values of the associativity change counters in the
> @@ -1293,11 +1294,9 @@
>   */
>  static int update_cpu_associativity_changes_mask(void)
>  {
> -	int cpu, nr_cpus = 0;
> +	int cpu;
>  	cpumask_t *changes = &cpu_associativity_changes_mask;
>  
> -	cpumask_clear(changes);
> -
>  	for_each_possible_cpu(cpu) {
>  		int i, changed = 0;
>  		u8 *counts = vphn_cpu_change_counts[cpu];
> @@ -1311,11 +1310,10 @@
>  		}
>  		if (changed) {
>  			cpumask_set_cpu(cpu, changes);
> -			nr_cpus++;
>  		}
>  	}
>  
> -	return nr_cpus;
> +	return cpumask_weight(changes);
>  }
>  
>  /*
> @@ -1416,7 +1414,7 @@
>  	unsigned int associativity[VPHN_ASSOC_BUFSIZE] = {0};
>  	struct device *dev;
>  
> -	for_each_cpu(cpu,&cpu_associativity_changes_mask) {
> +	for_each_cpu(cpu, &cpu_associativity_changes_mask) {
>  		vphn_get_associativity(cpu, associativity);
>  		nid = associativity_to_nid(associativity);
>  
> @@ -1438,6 +1436,7 @@
>  		dev = get_cpu_device(cpu);
>  		if (dev)
>  			kobject_uevent(&dev->kobj, KOBJ_CHANGE);
> +		cpumask_clear_cpu(cpu, &cpu_associativity_changes_mask);
>  		changed = 1;
>  	}
>  
> @@ -1457,37 +1456,80 @@
>  
>  static void topology_timer_fn(unsigned long ignored)
>  {
> -	if (!vphn_enabled)
> -		return;
> -	if (update_cpu_associativity_changes_mask() > 0)
> +	if (prrn_enabled && cpumask_weight(&cpu_associativity_changes_mask))
>  		topology_schedule_update();
> -	set_topology_timer();
> +	else if (vphn_enabled) {
> +		if (update_cpu_associativity_changes_mask() > 0)
> +			topology_schedule_update();
> +		reset_topology_timer();
> +	}
>  }
>  static struct timer_list topology_timer =
>  	TIMER_INITIALIZER(topology_timer_fn, 0, 0);
>  
> -static void set_topology_timer(void)
> +static void reset_topology_timer(void)
>  {
>  	topology_timer.data = 0;
>  	topology_timer.expires = jiffies + 60 * HZ;
> -	add_timer(&topology_timer);
> +	mod_timer(&topology_timer, topology_timer.expires);
> +}
> +
> +static void stage_topology_update(int core_id)
> +{
> +	cpumask_or(&cpu_associativity_changes_mask,
> +		&cpu_associativity_changes_mask, cpu_sibling_mask(core_id));
> +	reset_topology_timer();
>  }
>  
> +static int dt_update_callback(struct notifier_block *nb,
> +				unsigned long action, void *data)
> +{
> +	struct of_prop_reconfig *update;
> +	int rc = NOTIFY_DONE;
> +
> +	switch (action) {
> +	case OF_RECONFIG_ADD_PROPERTY:
> +	case OF_RECONFIG_UPDATE_PROPERTY:
> +		update = (struct of_prop_reconfig *)data;
> +		if (!of_prop_cmp(update->dn->type, "cpu")) {
> +			u32 core_id;
> +			of_property_read_u32(update->dn, "reg", &core_id);
> +			stage_topology_update(core_id);
> +			rc = NOTIFY_OK;
> +		}
> +		break;
> +	}
> +
> +	return rc;
> +}
> +
> +static struct notifier_block dt_update_nb = {
> +	.notifier_call = dt_update_callback,
> +};
> +
>  /*
> - * Start polling for VPHN associativity changes.
> + * Start polling for associativity changes.
>   */
>  int start_topology_update(void)
>  {
>  	int rc = 0;
>  
> -	/* Disabled until races with load balancing are fixed */
> -	if (0 && firmware_has_feature(FW_FEATURE_VPHN) &&
> -	    get_lppaca()->shared_proc) {
> -		vphn_enabled = 1;
> -		setup_cpu_associativity_change_counters();
> -		init_timer_deferrable(&topology_timer);
> -		set_topology_timer();
> -		rc = 1;
> +	if (firmware_has_feature(FW_FEATURE_PRRN)) {
> +		if (!prrn_enabled) {
> +			prrn_enabled = 1;
> +			vphn_enabled = 0;
> +			rc = of_reconfig_notifier_register(&dt_update_nb);
> +		}
> +	} else if (0 && firmware_has_feature(FW_FEATURE_VPHN) &&
> +		   get_lppaca()->shared_proc) {
> +		/* Disabled until races with load balancing are fixed */
> +		if (!vphn_enabled) {
> +			prrn_enabled = 0;
> +			vphn_enabled = 1;
> +			setup_cpu_associativity_change_counters();
> +			init_timer_deferrable(&topology_timer);
> +			reset_topology_timer();
> +		}
>  	}
>  
>  	return rc;
> @@ -1499,7 +1541,16 @@
>   */
>  int stop_topology_update(void)
>  {
> -	vphn_enabled = 0;
> -	return del_timer_sync(&topology_timer);
> +	int rc = 0;
> +
> +	if (prrn_enabled) {
> +		prrn_enabled = 0;
> +		rc = of_reconfig_notifier_unregister(&dt_update_nb);
> +	} else if (vphn_enabled) {
> +		vphn_enabled = 0;
> +		rc = del_timer_sync(&topology_timer);
> +	}
> +
> +	return rc;
>  }
>  #endif /* CONFIG_PPC_SPLPAR */
> Index: powerpc/arch/powerpc/include/asm/firmware.h
> ===================================================================
> --- powerpc.orig/arch/powerpc/include/asm/firmware.h	2013-04-15 14:03:52.000000000 -0500
> +++ powerpc/arch/powerpc/include/asm/firmware.h	2013-04-15 14:04:47.000000000 -0500
> @@ -52,6 +52,7 @@
>  #define FW_FEATURE_SET_MODE	ASM_CONST(0x0000000040000000)
>  #define FW_FEATURE_BEST_ENERGY	ASM_CONST(0x0000000080000000)
>  #define FW_FEATURE_TYPE1_AFFINITY ASM_CONST(0x0000000100000000)
> +#define FW_FEATURE_PRRN		ASM_CONST(0x0000000200000000)
>  
>  #ifndef __ASSEMBLY__
>  
> @@ -67,7 +68,7 @@
>  		FW_FEATURE_MULTITCE | FW_FEATURE_SPLPAR | FW_FEATURE_LPAR |
>  		FW_FEATURE_CMO | FW_FEATURE_VPHN | FW_FEATURE_XCMO |
>  		FW_FEATURE_SET_MODE | FW_FEATURE_BEST_ENERGY |
> -		FW_FEATURE_TYPE1_AFFINITY,
> +		FW_FEATURE_TYPE1_AFFINITY | FW_FEATURE_PRRN,
>  	FW_FEATURE_PSERIES_ALWAYS = 0,
>  	FW_FEATURE_POWERNV_POSSIBLE = FW_FEATURE_OPAL | FW_FEATURE_OPALv2,
>  	FW_FEATURE_POWERNV_ALWAYS = 0,
> Index: powerpc/arch/powerpc/platforms/pseries/firmware.c
> ===================================================================
> --- powerpc.orig/arch/powerpc/platforms/pseries/firmware.c	2013-04-15 14:03:52.000000000 -0500
> +++ powerpc/arch/powerpc/platforms/pseries/firmware.c	2013-04-15 14:04:47.000000000 -0500
> @@ -113,6 +113,7 @@
>  static __initdata struct vec5_fw_feature
>  vec5_fw_features_table[FIRMWARE_MAX_FEATURES] = {
>  	{FW_FEATURE_TYPE1_AFFINITY,	OV5_TYPE1_AFFINITY},
> +	{FW_FEATURE_PRRN,		OV5_PRRN},
>  };
>  
>  void __init fw_vec5_feature_init(const char *vec5, unsigned long len)
> 
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