[PATCH 1/2] powerpc/papr_scm: Fetch nvdimm performance stats from PHYP
Vaibhav Jain
vaibhav at linux.ibm.com
Thu Jun 25 00:58:57 AEST 2020
Thanks for reviewing this patch Ira,
My responses below inline.
Ira Weiny <ira.weiny at intel.com> writes:
> On Mon, Jun 22, 2020 at 09:54:50AM +0530, Vaibhav Jain wrote:
>> 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 'len_stat_buffer'.
>>
>> 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
>> 'len_stat_buffer' 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: Vaibhav Jain <vaibhav at linux.ibm.com>
>> ---
>> Documentation/ABI/testing/sysfs-bus-papr-pmem | 27 ++++
>> arch/powerpc/platforms/pseries/papr_scm.c | 139 ++++++++++++++++++
>> 2 files changed, 166 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-bus-papr-pmem b/Documentation/ABI/testing/sysfs-bus-papr-pmem
>> index 5b10d036a8d4..c1a67275c43f 100644
>> --- a/Documentation/ABI/testing/sysfs-bus-papr-pmem
>> +++ b/Documentation/ABI/testing/sysfs-bus-papr-pmem
>> @@ -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 at lists.ozlabs.org>, linux-nvdimm at 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
>> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
>> index 9c569078a09f..cb3f9acc325b 100644
>> --- a/arch/powerpc/platforms/pseries/papr_scm.c
>> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
>> @@ -62,6 +62,24 @@
>> 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 statistic_id[8];
>> + u64 statistic_value;
>> +};
>> +
>> +/* Struct exchanged between kernel and PHYP for fetching drc perf stats */
>> +struct papr_scm_perf_stats {
>> + u8 eye_catcher[8];
>> + u32 stats_version; /* Should be 0x01 */
> ^^^^
> PAPR_SCM_PERF_STATS_VERSION?
Sure. Will update in v2
>
>> + u32 num_statistics; /* Number of stats following */
>> + /* 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;
>> @@ -89,6 +107,9 @@ struct papr_scm_priv {
>>
>> /* Health information for the dimm */
>> u64 health_bitmap;
>> +
>> + /* length of the stat buffer as expected by phyp */
>> + size_t len_stat_buffer;
>> };
>>
>> static int drc_pmem_bind(struct papr_scm_priv *p)
>> @@ -194,6 +215,75 @@ static int drc_pmem_query_n_bind(struct papr_scm_priv *p)
>> 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' of 'size' in bytes.
>> + * The value of R4 is copied to 'out' if the pointer is provided.
>> + */
>> +static int drc_pmem_query_stats(struct papr_scm_priv *p,
>> + struct papr_scm_perf_stats *buff_stats,
>> + size_t size, unsigned int num_stats,
>> + uint64_t *out)
>> +{
>> + unsigned long ret[PLPAR_HCALL_BUFSIZE];
>> + struct papr_scm_perf_stat *stats;
>> + s64 rc, i;
>> +
>> + /* 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);
>> + } else {
>> + /* In case of no out buffer ignore the size */
>> + size = 0;
>> + }
>> +
>> + /*
>> + * Do the HCALL asking PHYP for info and if R4 was requested
>> + * return its value in 'out' variable.
>> + */
>> + rc = plpar_hcall(H_SCM_PERFORMANCE_STATS, ret, p->drc_index,
>> + virt_to_phys(buff_stats), size);
>
> You are calling virt_to_phys(NULL) here when called from
> papr_scm_nvdimm_init()! That can't be right.
Thanks for cathing this. However if the 'size' is '0' the 'buff_stats'
address is ignored by the hypervisor hence this didnt get caught in my
tests. Though CONFIG_DEBUG_VIRTUAL would have caught it early.
>
>> + if (out)
>> + *out = ret[0];
>> +
>> + 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 -ENXIO;
>> + }
>> +
>> + /* Successfully fetched the requested stats from phyp */
>> + if (size != 0) {
>> + buff_stats->num_statistics =
>> + be32_to_cpu(buff_stats->num_statistics);
>> +
>> + /* Transform the stats buffer values from BE to cpu native */
>> + for (i = 0, stats = buff_stats->scm_statistic;
>> + i < buff_stats->num_statistics; ++i) {
>> + stats[i].statistic_value =
>> + be64_to_cpu(stats[i].statistic_value);
>> + }
>> + dev_dbg(&p->pdev->dev,
>> + "Performance stats returned %d stats\n",
>> + buff_stats->num_statistics);
>> + } else {
>> + /* Handle case where stat buffer size was requested */
>> + dev_dbg(&p->pdev->dev,
>> + "Performance stats size %ld\n", ret[0]);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> /*
>> * Issue hcall to retrieve dimm health info and populate papr_scm_priv with the
>> * health information.
>> @@ -631,6 +721,45 @@ 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->len_stat_buffer)
>> + return -ENOENT;
>> +
>> + /* Allocate the buffer for phyp where stats are written */
>> + stats = kzalloc(p->len_stat_buffer, GFP_KERNEL);
>
> I'm concerned that this buffer does not seem to have anything to do with the
> 'num_stats' parameter passed to drc_pmem_query_stats(). Furthermore why is
> num_stats always 0 in those calls?
>
'num_stats == 0' is a special case of the hcall where PHYP returns all
the possible stats in the 'stats' buffer.
>> + if (!stats)
>> + return -ENOMEM;
>> +
>> + /* Ask phyp to return all dimm perf stats */
>> + rc = drc_pmem_query_stats(p, stats, p->len_stat_buffer, 0, NULL);
>> + if (!rc) {
>> + /*
>> + * Go through the returned output buffer and print stats and
>> + * values. Since statistic_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 < stats->num_statistics; ++index, ++stat) {
>> + seq_buf_printf(&s, "%.8s = 0x%016llX\n",
>> + stat->statistic_id, stat->statistic_value);
>> + }
>> + }
>> +
>> + 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)
>> {
>> @@ -676,6 +805,7 @@ 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,
>> };
>>
>> @@ -696,6 +826,7 @@ 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;
>> + u64 stat_size;
>>
>> p->bus_desc.ndctl = papr_scm_ndctl;
>> p->bus_desc.module = THIS_MODULE;
>> @@ -759,6 +890,14 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
>> dev_info(dev, "Region registered with target node %d and online node %d",
>> target_nid, online_nid);
>>
>> + /* Try retriving the stat buffer and see if its supported */
>> + if (!drc_pmem_query_stats(p, NULL, 0, 0, &stat_size)) {
>> + p->len_stat_buffer = (size_t)stat_size;
>> + dev_dbg(&p->pdev->dev, "Max perf-stat size %lu-bytes\n",
>> + p->len_stat_buffer);
>> + } else {
>> + dev_info(&p->pdev->dev, "Limited dimm stat info available\n");
>
> Do we really need this print?
nvdimm performance stats can be selectively turned on/off from the
hypervisor management console hence this info message is more like a
warning indicating that extended dimm stat info like 'fuel_gauge' is not
available.
>
> Ira
>
>> + }
>> return 0;
>>
>> err: nvdimm_bus_unregister(p->bus);
>> --
>> 2.26.2
>> _______________________________________________
>> Linux-nvdimm mailing list -- linux-nvdimm at lists.01.org
>> To unsubscribe send an email to linux-nvdimm-leave at lists.01.org
--
Cheers
~ Vaibhav
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