Re: [PATCH v1 2/2] powerpc/pseries: Add debugfs interface to retrieve VPHN info

["Naveen N. Rao" <naveen.n.rao@linux.ibm.com>]

Hi Michael,

Naveen N. Rao wrote:
> Add debugfs interface to retrieve associativity information for lpar
> vcpus (debugfs/vphn/lpar) and the hypervisor cpus (debugfs/vphn/hyp).
> This information is useful to derive various metrics, including the vcpu
> dispatch statistics in a SPLPAR environment.

Any thoughts on this approach vs. adding a tracepoint?


Thanks,
Naveen

> 
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
> ---
>  arch/powerpc/mm/numa.c | 105 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 105 insertions(+)
> 
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index 6677a578f18d..f0b0e87016e6 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -40,6 +40,7 @@
>  #include <asm/setup.h>
>  #include <asm/vdso.h>
>  #include <asm/drmem.h>
> +#include <asm/debugfs.h>
>  
>  static int numa_enabled = 1;
>  
> @@ -1089,6 +1090,107 @@ static long hcall_vphn(unsigned long cpu, u64 flags, __be32 *associativity)
>  	return rc;
>  }
>  
> +#ifdef CONFIG_DEBUG_FS
> +static ssize_t vphn_lpar_cpu_file_read(struct file *filp, char __user *buf,
> +		size_t len, loff_t *pos)
> +{
> +	int cpu = (long)filp->private_data;
> +	__be32 associativity[VPHN_ASSOC_BUFSIZE] = {0};
> +	int hwcpu = get_hard_smp_processor_id(cpu);
> +	long int rc;
> +
> +	if (len != sizeof(associativity))
> +		return -EINVAL;
> +
> +	rc = hcall_vphn(hwcpu, 1, associativity);
> +	if (rc)
> +		return -EFAULT;
> +
> +	rc = copy_to_user(buf, &associativity, sizeof(associativity));
> +	if (rc)
> +		return -EFAULT;
> +
> +	return sizeof(associativity);
> +}
> +
> +static ssize_t vphn_hyp_cpu_file_read(struct file *filp, char __user *buf,
> +		size_t len, loff_t *pos)
> +{
> +	int cpu = (long)filp->private_data;
> +	__be32 associativity[VPHN_ASSOC_BUFSIZE] = {0};
> +	long int rc;
> +
> +	if (len != sizeof(associativity))
> +		return -EINVAL;
> +
> +	rc = hcall_vphn(cpu, 2, associativity);
> +	if (rc)
> +		return -EFAULT;
> +
> +	rc = copy_to_user(buf, &associativity, sizeof(associativity));
> +	if (rc)
> +		return -EFAULT;
> +
> +	return sizeof(associativity);
> +}
> +
> +static const struct file_operations vphn_lpar_cpu_fops = {
> +	.open		= simple_open,
> +	.read		= vphn_lpar_cpu_file_read,
> +	.llseek		= no_llseek,
> +};
> +
> +static const struct file_operations vphn_hyp_cpu_fops = {
> +	.open		= simple_open,
> +	.read		= vphn_hyp_cpu_file_read,
> +	.llseek		= no_llseek,
> +};
> +
> +static int debug_init_vphn_entries(void)
> +{
> +	struct dentry *vphn_dir, *vphn_lpar_dir, *vphn_hyp_dir;
> +	struct dentry *vphn_lpar_cpu_file, *vphn_hyp_cpu_file;
> +	long cpu;
> +	char name[10];
> +
> +	if (!firmware_has_feature(FW_FEATURE_SPLPAR))
> +		return 0;
> +
> +	vphn_dir = debugfs_create_dir("vphn", powerpc_debugfs_root);
> +	if (!vphn_dir) {
> +		pr_warn("%s: can't create vphn debugfs root dir\n", __func__);
> +		return -ENOMEM;
> +	}
> +
> +	vphn_lpar_dir = debugfs_create_dir("lpar", vphn_dir);
> +	vphn_hyp_dir = debugfs_create_dir("hyp", vphn_dir);
> +	if (!vphn_lpar_dir || !vphn_hyp_dir) {
> +		pr_warn("%s: can't create vphn dir\n", __func__);
> +		goto err_remove_dir;
> +	}
> +
> +	for_each_possible_cpu(cpu) {
> +		sprintf(name, "cpu-%ld", cpu);
> +		vphn_lpar_cpu_file = debugfs_create_file(name, 0400,
> +				vphn_lpar_dir, (void *)cpu, &vphn_lpar_cpu_fops);
> +		vphn_hyp_cpu_file = debugfs_create_file(name, 0400,
> +				vphn_hyp_dir, (void *)cpu, &vphn_hyp_cpu_fops);
> +		if (!vphn_lpar_cpu_file || !vphn_hyp_cpu_file) {
> +			pr_warn("%s: can't create vphn cpu file\n", __func__);
> +			goto err_remove_dir;
> +		}
> +	}
> +
> +	return 0;
> +
> +err_remove_dir:
> +	debugfs_remove_recursive(vphn_dir);
> +	return -ENOMEM;
> +}
> +#else
> +static int debug_init_vphn_entries(void) { return 0; }
> +#endif /* CONFIG_DEBUG_FS */
> +
>  /*
>   * Change polling interval for associativity changes.
>   */
> @@ -1619,6 +1721,9 @@ static int topology_update_init(void)
>  	if (!proc_create("powerpc/topology_updates", 0644, NULL, &topology_ops))
>  		return -ENOMEM;
>  
> +	if (!debug_init_vphn_entries())
> +		return -ENOMEM;
> +
>  	topology_inited = 1;
>  	return 0;
>  }
> -- 
> 2.19.2
> 
> 
>