Commit 2d02bf83 authored by Vaibhav Jain's avatar Vaibhav Jain Committed by Michael Ellerman
Browse files

powerpc/papr_scm: Fetch nvdimm performance stats from PHYP 



Update papr_scm.c to query dimm performance statistics from PHYP via
H_SCM_PERFORMANCE_STATS hcall and export them to user-space as PAPR
specific NVDIMM attribute 'perf_stats' in sysfs. The patch also
provide a sysfs ABI documentation for the stats being reported and
their meanings.

During NVDIMM probe time in papr_scm_nvdimm_init() a special variant
of H_SCM_PERFORMANCE_STATS hcall is issued to check if collection of
performance statistics is supported or not. If successful then a PHYP
returns a maximum possible buffer length needed to read all
performance stats. This returned value is stored in a per-nvdimm
attribute 'stat_buffer_len'.

The layout of request buffer for reading NVDIMM performance stats from
PHYP is defined in 'struct papr_scm_perf_stats' and 'struct
papr_scm_perf_stat'. These structs are used in newly introduced
drc_pmem_query_stats() that issues the H_SCM_PERFORMANCE_STATS hcall.

The sysfs access function perf_stats_show() uses value
'stat_buffer_len' to allocate a buffer large enough to hold all
possible NVDIMM performance stats and passes it to
drc_pmem_query_stats() to populate. Finally statistics reported in the
buffer are formatted into the sysfs access function output buffer.

Signed-off-by: default avatarVaibhav Jain <vaibhav@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200731064153.182203-2-vaibhav@linux.ibm.com
parent d947fb4c

Documentation/ABI/testing/sysfs-bus-papr-pmem

+27 −0
Original line number Diff line number Diff line
@@ -25,3 +25,30 @@ Description: 
				  NVDIMM have been scrubbed.

		* "locked"	: Indicating that NVDIMM contents cant

				  be modified until next power cycle.



What:		/sys/bus/nd/devices/nmemX/papr/perf_stats

Date:		May, 2020

KernelVersion:	v5.9

Contact:	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, linux-nvdimm@lists.01.org,

Description:

		(RO) Report various performance stats related to papr-scm NVDIMM

		device.  Each stat is reported on a new line with each line

		composed of a stat-identifier followed by it value. Below are

		currently known dimm performance stats which are reported:



		* "CtlResCt" : Controller Reset Count

		* "CtlResTm" : Controller Reset Elapsed Time

		* "PonSecs " : Power-on Seconds

		* "MemLife " : Life Remaining

		* "CritRscU" : Critical Resource Utilization

		* "HostLCnt" : Host Load Count

		* "HostSCnt" : Host Store Count

		* "HostSDur" : Host Store Duration

		* "HostLDur" : Host Load Duration

		* "MedRCnt " : Media Read Count

		* "MedWCnt " : Media Write Count

		* "MedRDur " : Media Read Duration

		* "MedWDur " : Media Write Duration

		* "CchRHCnt" : Cache Read Hit Count

		* "CchWHCnt" : Cache Write Hit Count

		* "FastWCnt" : Fast Write Count
 
 No newline at end of file

arch/powerpc/platforms/pseries/papr_scm.c

+150 −0
Original line number Diff line number Diff line
@@ -64,6 +64,26 @@ 
				    PAPR_PMEM_HEALTH_FATAL |	\

				    PAPR_PMEM_HEALTH_UNHEALTHY)



#define PAPR_SCM_PERF_STATS_EYECATCHER __stringify(SCMSTATS)

#define PAPR_SCM_PERF_STATS_VERSION 0x1



/* Struct holding a single performance metric */

struct papr_scm_perf_stat {

	u8 stat_id[8];

	__be64 stat_val;

} __packed;



/* Struct exchanged between kernel and PHYP for fetching drc perf stats */

struct papr_scm_perf_stats {

	u8 eye_catcher[8];

	/* Should be PAPR_SCM_PERF_STATS_VERSION */

	__be32 stats_version;

	/* Number of stats following */

	__be32 num_statistics;

	/* zero or more performance matrics */

	struct papr_scm_perf_stat scm_statistic[];

} __packed;



/* private struct associated with each region */

struct papr_scm_priv {

	struct platform_device *pdev;
@@ -92,6 +112,9 @@ struct papr_scm_priv { 


	/* Health information for the dimm */

	u64 health_bitmap;



	/* length of the stat buffer as expected by phyp */

	size_t stat_buffer_len;

};



static LIST_HEAD(papr_nd_regions);
@@ -200,6 +223,79 @@ err_out: 
	return drc_pmem_bind(p);

}



/*

 * Query the Dimm performance stats from PHYP and copy them (if returned) to

 * provided struct papr_scm_perf_stats instance 'stats' that can hold atleast

 * (num_stats + header) bytes.

 * - If buff_stats == NULL the return value is the size in byes of the buffer

 * needed to hold all supported performance-statistics.

 * - If buff_stats != NULL and num_stats == 0 then we copy all known

 * performance-statistics to 'buff_stat' and expect to be large enough to

 * hold them.

 * - if buff_stats != NULL and num_stats > 0 then copy the requested

 * performance-statistics to buff_stats.

 */

static ssize_t drc_pmem_query_stats(struct papr_scm_priv *p,

				    struct papr_scm_perf_stats *buff_stats,

				    unsigned int num_stats)

{

	unsigned long ret[PLPAR_HCALL_BUFSIZE];

	size_t size;

	s64 rc;



	/* Setup the out buffer */

	if (buff_stats) {

		memcpy(buff_stats->eye_catcher,

		       PAPR_SCM_PERF_STATS_EYECATCHER, 8);

		buff_stats->stats_version =

			cpu_to_be32(PAPR_SCM_PERF_STATS_VERSION);

		buff_stats->num_statistics =

			cpu_to_be32(num_stats);



		/*

		 * Calculate the buffer size based on num-stats provided

		 * or use the prefetched max buffer length

		 */

		if (num_stats)

			/* Calculate size from the num_stats */

			size = sizeof(struct papr_scm_perf_stats) +

				num_stats * sizeof(struct papr_scm_perf_stat);

		else

			size = p->stat_buffer_len;

	} else {

		/* In case of no out buffer ignore the size */

		size = 0;

	}



	/* Do the HCALL asking PHYP for info */

	rc = plpar_hcall(H_SCM_PERFORMANCE_STATS, ret, p->drc_index,

			 buff_stats ? virt_to_phys(buff_stats) : 0,

			 size);



	/* Check if the error was due to an unknown stat-id */

	if (rc == H_PARTIAL) {

		dev_err(&p->pdev->dev,

			"Unknown performance stats, Err:0x%016lX\n", ret[0]);

		return -ENOENT;

	} else if (rc != H_SUCCESS) {

		dev_err(&p->pdev->dev,

			"Failed to query performance stats, Err:%lld\n", rc);

		return -EIO;



	} else if (!size) {

		/* Handle case where stat buffer size was requested */

		dev_dbg(&p->pdev->dev,

			"Performance stats size %ld\n", ret[0]);

		return ret[0];

	}



	/* Successfully fetched the requested stats from phyp */

	dev_dbg(&p->pdev->dev,

		"Performance stats returned %d stats\n",

		be32_to_cpu(buff_stats->num_statistics));

	return 0;

}



/*

 * Issue hcall to retrieve dimm health info and populate papr_scm_priv with the

 * health information.
@@ -637,6 +733,48 @@ static int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc, 
	return 0;

}



static ssize_t perf_stats_show(struct device *dev,

			       struct device_attribute *attr, char *buf)

{

	int index, rc;

	struct seq_buf s;

	struct papr_scm_perf_stat *stat;

	struct papr_scm_perf_stats *stats;

	struct nvdimm *dimm = to_nvdimm(dev);

	struct papr_scm_priv *p = nvdimm_provider_data(dimm);



	if (!p->stat_buffer_len)

		return -ENOENT;



	/* Allocate the buffer for phyp where stats are written */

	stats = kzalloc(p->stat_buffer_len, GFP_KERNEL);

	if (!stats)

		return -ENOMEM;



	/* Ask phyp to return all dimm perf stats */

	rc = drc_pmem_query_stats(p, stats, 0);

	if (rc)

		goto free_stats;

	/*

	 * Go through the returned output buffer and print stats and

	 * values. Since stat_id is essentially a char string of

	 * 8 bytes, simply use the string format specifier to print it.

	 */

	seq_buf_init(&s, buf, PAGE_SIZE);

	for (index = 0, stat = stats->scm_statistic;

	     index < be32_to_cpu(stats->num_statistics);

	     ++index, ++stat) {

		seq_buf_printf(&s, "%.8s = 0x%016llX\n",

			       stat->stat_id,

			       be64_to_cpu(stat->stat_val));

	}



free_stats:

	kfree(stats);

	return rc ? rc : seq_buf_used(&s);

}

DEVICE_ATTR_RO(perf_stats);



static ssize_t flags_show(struct device *dev,

			  struct device_attribute *attr, char *buf)

{
@@ -682,6 +820,7 @@ DEVICE_ATTR_RO(flags); 
/* papr_scm specific dimm attributes */

static struct attribute *papr_nd_attributes[] = {

	&dev_attr_flags.attr,

	&dev_attr_perf_stats.attr,

	NULL,

};
@@ -702,6 +841,7 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p) 
	struct nd_region_desc ndr_desc;

	unsigned long dimm_flags;

	int target_nid, online_nid;

	ssize_t stat_size;



	p->bus_desc.ndctl = papr_scm_ndctl;

	p->bus_desc.module = THIS_MODULE;
@@ -769,6 +909,16 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p) 
	list_add_tail(&p->region_list, &papr_nd_regions);

	mutex_unlock(&papr_ndr_lock);



	/* Try retriving the stat buffer and see if its supported */

	stat_size = drc_pmem_query_stats(p, NULL, 0);

	if (stat_size > 0) {

		p->stat_buffer_len = stat_size;

		dev_dbg(&p->pdev->dev, "Max perf-stat size %lu-bytes\n",

			p->stat_buffer_len);

	} else {

		dev_info(&p->pdev->dev, "Dimm performance stats unavailable\n");

	}



	return 0;



err:	nvdimm_bus_unregister(p->bus);

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