Thanks for reviewing this patch Ira, My responses below inline.
Ira Weiny <ira.we...@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 <vaib...@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-...@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 >> 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@lists.01.org >> To unsubscribe send an email to linux-nvdimm-le...@lists.01.org -- Cheers ~ Vaibhav _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-le...@lists.01.org