| Message ID | 20201108211549.122018-1-vaibhav@linux.ibm.com (mailing list archive) |
|---|---|
| State | RFC |
| Headers | show |
| Series | [RFC,1/2] libnvdimm: Introduce ND_CMD_GET_STAT to retrieve nvdimm statistics | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (80ecbe16c827714ce3741ed1f1d34488b903e717) |
| snowpatch_ozlabs/checkpatch | warning | total: 0 errors, 1 warnings, 0 checks, 189 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
[ add perf maintainers ] On Sun, Nov 8, 2020 at 1:16 PM Vaibhav Jain <vaibhav@linux.ibm.com> wrote: > > Implement support for exposing generic nvdimm statistics via newly > introduced dimm-command ND_CMD_GET_STAT that can be handled by nvdimm > command handler function and provide values for these statistics back > to libnvdimm. Following generic nvdimm statistics are defined as an > enumeration in 'uapi/ndctl.h': > > * "media_reads" : Number of media reads that have occurred since reboot. > * "media_writes" : Number of media writes that have occurred since reboot. > * "read_requests" : Number of read requests that have occurred since reboot. > * "write_requests" : Number of write requests that have occurred since reboot. Perhaps document these as "since device reset"? As I can imagine some devices might have a mechanism to reset the count outside of "reboot" which is a bit ambiguous. > * "total_media_reads" : Total number of media reads that have occurred. > * "total_media_writes" : Total number of media writes that have occurred. > * "total_read_requests" : Total number of read requests that have occurred. > * "total_write_requests" : Total number of write requests that have occurred. > > Apart from ND_CMD_GET_STAT ioctl these nvdimm statistics are also > exposed via sysfs '<nvdimm-device>/stats' directory for easy user-space > access like below: > > /sys/class/nd/ndctl0/device/nmem0/stats # tail -n +1 * > ==> media_reads <== > 252197707602 > ==> media_writes <== > 20684685172 > ==> read_requests <== > 658810924962 > ==> write_requests <== > 404464081574 Hmm, I haven't looked but how hard would it be to plumb these to be perf counter-events. So someone could combine these with other perf counters? > In case a specific nvdimm-statistic is not supported than nvdimm > command handler function can simply return an error (e.g -ENOENT) for > request to read that nvdimm-statistic. Makes sense, but I expect the perf route also has a way to enumerate which statistics / counters are supported. I'm not opposed to also having them in sysfs, but I think perf support should be a first class citizen. > > The value for a specific nvdimm-stat is exchanged via newly introduced > 'struct nd_cmd_get_dimm_stat' that hold a single statistics and a > union of possible values types. Presently only '__s64' type of generic > attributes are supported. These attributes are defined in > 'ndvimm/dimm_devs.c' via a helper macro 'NVDIMM_STAT_ATTR'. > > Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com> > --- > drivers/nvdimm/bus.c | 6 ++ > drivers/nvdimm/dimm_devs.c | 109 +++++++++++++++++++++++++++++++++++++ > drivers/nvdimm/nd.h | 5 ++ > include/uapi/linux/ndctl.h | 27 +++++++++ > 4 files changed, 147 insertions(+) > > diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c > index 2304c6183822..d53564477437 100644 > --- a/drivers/nvdimm/bus.c > +++ b/drivers/nvdimm/bus.c > @@ -794,6 +794,12 @@ static const struct nd_cmd_desc __nd_cmd_dimm_descs[] = { > .out_num = 1, > .out_sizes = { UINT_MAX, }, > }, > + [ND_CMD_GET_STAT] = { > + .in_num = 1, > + .in_sizes = { sizeof(struct nd_cmd_get_dimm_stat), }, > + .out_num = 1, > + .out_sizes = { sizeof(struct nd_cmd_get_dimm_stat), }, > + }, > }; > > const struct nd_cmd_desc *nd_cmd_dimm_desc(int cmd) > diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c > index b59032e0859b..68aaa294def7 100644 > --- a/drivers/nvdimm/dimm_devs.c > +++ b/drivers/nvdimm/dimm_devs.c > @@ -555,6 +555,114 @@ static umode_t nvdimm_firmware_visible(struct kobject *kobj, struct attribute *a > return a->mode; > } > > +/* Request a dimm stat from the bus driver */ > +static int __request_dimm_stat(struct nvdimm_bus *nvdimm_bus, > + struct nvdimm *dimm, u64 stat_id, > + s64 *stat_val) > +{ > + struct nvdimm_bus_descriptor *nd_desc = nvdimm_bus->nd_desc; > + struct nd_cmd_get_dimm_stat stat = { .stat_id = stat_id }; > + int rc, cmd_rc; > + > + if (!test_bit(ND_CMD_GET_STAT, &dimm->cmd_mask)) { > + pr_debug("CMD_GET_STAT not set for bus driver 0x%lx\n", > + nd_desc->cmd_mask); > + return -ENOENT; > + } > + > + /* Is stat requested is known & bus driver supports fetching stats */ > + if (stat_id <= ND_DIMM_STAT_INVALID || stat_id > ND_DIMM_STAT_MAX) { > + WARN(1, "Unknown stat-id(%llu) requested", stat_id); > + return -ENOENT; > + } > + > + /* Ask bus driver for its stat value */ > + rc = nd_desc->ndctl(nd_desc, dimm, ND_CMD_GET_STAT, > + &stat, sizeof(stat), &cmd_rc); > + if (rc || cmd_rc) { > + pr_debug("Unable to request stat %lld. Error (%d,%d)\n", > + stat_id, rc, cmd_rc); > + return rc ? rc : cmd_rc; > + } > + > + /* Indicate error in case returned struct doesn't have the stat_id set */ > + if (stat.stat_id != stat_id) { > + pr_debug("Invalid statid %llu returned\n", stat.stat_id); > + return -ENOENT; > + } > + > + *stat_val = stat.int_val; > + return 0; > +} > + > +static ssize_t nvdimm_stat_attr_show(struct device *dev, > + struct device_attribute *attr, > + char *buf) > +{ > + struct nvdimm_stat_attr *nattr = container_of(attr, typeof(*nattr), attr); > + struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(dev); > + struct nvdimm *nvdimm = to_nvdimm(dev); > + s64 stat_val; > + int rc; > + > + rc = __request_dimm_stat(nvdimm_bus, nvdimm, nattr->stat_id, &stat_val); > + > + if (rc) > + return rc; > + > + return snprintf(buf, PAGE_SIZE, "%lld", stat_val); > +} > + > +static umode_t nvdimm_stats_visible(struct kobject *kobj, struct attribute *a, int n) > +{ > + struct nvdimm_stat_attr *nattr = container_of(a, typeof(*nattr), attr.attr); > + struct device *dev = container_of(kobj, typeof(*dev), kobj); > + struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(dev); > + struct nvdimm *nvdimm = to_nvdimm(dev); > + u64 stat_val; > + int rc; > + > + /* request dimm stat from bus driver and is success mark attribute as visible */ > + rc = __request_dimm_stat(nvdimm_bus, nvdimm, nattr->stat_id, &stat_val); > + if (rc) > + pr_info("Unable to query stat %llu . Error(%d)\n", nattr->stat_id, rc); > + > + return rc ? 0 : a->mode; > +} > + > +#define NVDIMM_STAT_ATTR(_name, _stat_id) \ > + struct nvdimm_stat_attr nvdimm_stat_attr_##_name = { \ > + .attr = __ATTR(_name, 0400, nvdimm_stat_attr_show, NULL), \ > + .stat_id = _stat_id, \ > + } > + > +static NVDIMM_STAT_ATTR(media_reads, ND_DIMM_STAT_MEDIA_READS); > +static NVDIMM_STAT_ATTR(media_writes, ND_DIMM_STAT_MEDIA_WRITES); > +static NVDIMM_STAT_ATTR(read_requests, ND_DIMM_STAT_READ_REQUESTS); > +static NVDIMM_STAT_ATTR(write_requests, ND_DIMM_STAT_WRITE_REQUESTS); > +static NVDIMM_STAT_ATTR(total_media_reads, ND_DIMM_STAT_TOTAL_MEDIA_READS); > +static NVDIMM_STAT_ATTR(total_media_writes, ND_DIMM_STAT_TOTAL_MEDIA_WRITES); > +static NVDIMM_STAT_ATTR(total_read_requests, ND_DIMM_STAT_TOTAL_READ_REQUESTS); > +static NVDIMM_STAT_ATTR(total_write_requests, ND_DIMM_STAT_TOTAL_WRITE_REQUESTS); > + > +static struct attribute *nvdimm_stats_attributes[] = { > + &nvdimm_stat_attr_media_reads.attr.attr, > + &nvdimm_stat_attr_media_writes.attr.attr, > + &nvdimm_stat_attr_read_requests.attr.attr, > + &nvdimm_stat_attr_write_requests.attr.attr, > + &nvdimm_stat_attr_total_media_reads.attr.attr, > + &nvdimm_stat_attr_total_media_writes.attr.attr, > + &nvdimm_stat_attr_total_read_requests.attr.attr, > + &nvdimm_stat_attr_total_write_requests.attr.attr, > + NULL, > +}; > + > +static const struct attribute_group nvdimm_stats_group = { > + .name = "stats", > + .attrs = nvdimm_stats_attributes, > + .is_visible = nvdimm_stats_visible, > +}; > + > static const struct attribute_group nvdimm_firmware_attribute_group = { > .name = "firmware", > .attrs = nvdimm_firmware_attributes, > @@ -565,6 +673,7 @@ static const struct attribute_group *nvdimm_attribute_groups[] = { > &nd_device_attribute_group, > &nvdimm_attribute_group, > &nvdimm_firmware_attribute_group, > + &nvdimm_stats_group, > NULL, > }; > > diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h > index 696b55556d4d..ea9e846ae245 100644 > --- a/drivers/nvdimm/nd.h > +++ b/drivers/nvdimm/nd.h > @@ -223,6 +223,11 @@ enum nd_async_mode { > ND_ASYNC, > }; > > +struct nvdimm_stat_attr { > + struct device_attribute attr; > + u64 stat_id; > +}; > + > int nd_integrity_init(struct gendisk *disk, unsigned long meta_size); > void wait_nvdimm_bus_probe_idle(struct device *dev); > void nd_device_register(struct device *dev); > diff --git a/include/uapi/linux/ndctl.h b/include/uapi/linux/ndctl.h > index 8cf1e4884fd5..81b76986b423 100644 > --- a/include/uapi/linux/ndctl.h > +++ b/include/uapi/linux/ndctl.h > @@ -97,6 +97,31 @@ struct nd_cmd_clear_error { > __u64 cleared; > } __packed; > > +/* Various generic dimm stats that can be reported */ > +enum { > + ND_DIMM_STAT_INVALID = 0, > + ND_DIMM_STAT_MEDIA_READS = 1, /* Media reads after power cycle */ > + ND_DIMM_STAT_MEDIA_WRITES = 2, /* Media writes after power cycle */ > + ND_DIMM_STAT_READ_REQUESTS = 3, /* Read requests after power cycle */ > + ND_DIMM_STAT_WRITE_REQUESTS = 4, /* Write requests after power cycle */ > + ND_DIMM_STAT_TOTAL_MEDIA_READS = 5, /* Total Media Reads */ > + ND_DIMM_STAT_TOTAL_MEDIA_WRITES = 6, /* Total Media Writes */ > + ND_DIMM_STAT_TOTAL_READ_REQUESTS = 7, /* Total Read Requests */ > + ND_DIMM_STAT_TOTAL_WRITE_REQUESTS = 8, /* Total Write Requests */ > + ND_DIMM_STAT_MAX = 8, > +}; > + > +struct nd_cmd_get_dimm_stat { > + /* See enum above for valid values */ > + __u64 stat_id; > + > + /* Holds a single dimm stat value */ > + union { > + __s64 int_val; > + char str_val[120]; > + }; > +} __packed; Is this needed? Especially if perf has the counters, and sysfs optionally has the counters, does the ioctl path also need to be plumbed?
On Mon, Dec 07, 2020 at 04:54:21PM -0800, Dan Williams wrote: > [ add perf maintainers ] > > On Sun, Nov 8, 2020 at 1:16 PM Vaibhav Jain <vaibhav@linux.ibm.com> wrote: > > > > Implement support for exposing generic nvdimm statistics via newly > > introduced dimm-command ND_CMD_GET_STAT that can be handled by nvdimm > > command handler function and provide values for these statistics back > > to libnvdimm. Following generic nvdimm statistics are defined as an > > enumeration in 'uapi/ndctl.h': > > > > * "media_reads" : Number of media reads that have occurred since reboot. > > * "media_writes" : Number of media writes that have occurred since reboot. > > * "read_requests" : Number of read requests that have occurred since reboot. > > * "write_requests" : Number of write requests that have occurred since reboot. > > Perhaps document these as "since device reset"? As I can imagine some > devices might have a mechanism to reset the count outside of "reboot" > which is a bit ambiguous. > > > * "total_media_reads" : Total number of media reads that have occurred. > > * "total_media_writes" : Total number of media writes that have occurred. > > * "total_read_requests" : Total number of read requests that have occurred. > > * "total_write_requests" : Total number of write requests that have occurred. > > > > Apart from ND_CMD_GET_STAT ioctl these nvdimm statistics are also > > exposed via sysfs '<nvdimm-device>/stats' directory for easy user-space > > access like below: > > > > /sys/class/nd/ndctl0/device/nmem0/stats # tail -n +1 * > > ==> media_reads <== > > 252197707602 > > ==> media_writes <== > > 20684685172 > > ==> read_requests <== > > 658810924962 > > ==> write_requests <== > > 404464081574 > > Hmm, I haven't looked but how hard would it be to plumb these to be > perf counter-events. So someone could combine these with other perf > counters? > > > In case a specific nvdimm-statistic is not supported than nvdimm > > command handler function can simply return an error (e.g -ENOENT) for > > request to read that nvdimm-statistic. > > Makes sense, but I expect the perf route also has a way to enumerate > which statistics / counters are supported. I'm not opposed to also > having them in sysfs, but I think perf support should be a first class > citizen. arch/x86/events/msr.c might be a good starting point for a software pmu delivering pure counters.
diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c index 2304c6183822..d53564477437 100644 --- a/drivers/nvdimm/bus.c +++ b/drivers/nvdimm/bus.c @@ -794,6 +794,12 @@ static const struct nd_cmd_desc __nd_cmd_dimm_descs[] = { .out_num = 1, .out_sizes = { UINT_MAX, }, }, + [ND_CMD_GET_STAT] = { + .in_num = 1, + .in_sizes = { sizeof(struct nd_cmd_get_dimm_stat), }, + .out_num = 1, + .out_sizes = { sizeof(struct nd_cmd_get_dimm_stat), }, + }, }; const struct nd_cmd_desc *nd_cmd_dimm_desc(int cmd) diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c index b59032e0859b..68aaa294def7 100644 --- a/drivers/nvdimm/dimm_devs.c +++ b/drivers/nvdimm/dimm_devs.c @@ -555,6 +555,114 @@ static umode_t nvdimm_firmware_visible(struct kobject *kobj, struct attribute *a return a->mode; } +/* Request a dimm stat from the bus driver */ +static int __request_dimm_stat(struct nvdimm_bus *nvdimm_bus, + struct nvdimm *dimm, u64 stat_id, + s64 *stat_val) +{ + struct nvdimm_bus_descriptor *nd_desc = nvdimm_bus->nd_desc; + struct nd_cmd_get_dimm_stat stat = { .stat_id = stat_id }; + int rc, cmd_rc; + + if (!test_bit(ND_CMD_GET_STAT, &dimm->cmd_mask)) { + pr_debug("CMD_GET_STAT not set for bus driver 0x%lx\n", + nd_desc->cmd_mask); + return -ENOENT; + } + + /* Is stat requested is known & bus driver supports fetching stats */ + if (stat_id <= ND_DIMM_STAT_INVALID || stat_id > ND_DIMM_STAT_MAX) { + WARN(1, "Unknown stat-id(%llu) requested", stat_id); + return -ENOENT; + } + + /* Ask bus driver for its stat value */ + rc = nd_desc->ndctl(nd_desc, dimm, ND_CMD_GET_STAT, + &stat, sizeof(stat), &cmd_rc); + if (rc || cmd_rc) { + pr_debug("Unable to request stat %lld. Error (%d,%d)\n", + stat_id, rc, cmd_rc); + return rc ? rc : cmd_rc; + } + + /* Indicate error in case returned struct doesn't have the stat_id set */ + if (stat.stat_id != stat_id) { + pr_debug("Invalid statid %llu returned\n", stat.stat_id); + return -ENOENT; + } + + *stat_val = stat.int_val; + return 0; +} + +static ssize_t nvdimm_stat_attr_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct nvdimm_stat_attr *nattr = container_of(attr, typeof(*nattr), attr); + struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(dev); + struct nvdimm *nvdimm = to_nvdimm(dev); + s64 stat_val; + int rc; + + rc = __request_dimm_stat(nvdimm_bus, nvdimm, nattr->stat_id, &stat_val); + + if (rc) + return rc; + + return snprintf(buf, PAGE_SIZE, "%lld", stat_val); +} + +static umode_t nvdimm_stats_visible(struct kobject *kobj, struct attribute *a, int n) +{ + struct nvdimm_stat_attr *nattr = container_of(a, typeof(*nattr), attr.attr); + struct device *dev = container_of(kobj, typeof(*dev), kobj); + struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(dev); + struct nvdimm *nvdimm = to_nvdimm(dev); + u64 stat_val; + int rc; + + /* request dimm stat from bus driver and is success mark attribute as visible */ + rc = __request_dimm_stat(nvdimm_bus, nvdimm, nattr->stat_id, &stat_val); + if (rc) + pr_info("Unable to query stat %llu . Error(%d)\n", nattr->stat_id, rc); + + return rc ? 0 : a->mode; +} + +#define NVDIMM_STAT_ATTR(_name, _stat_id) \ + struct nvdimm_stat_attr nvdimm_stat_attr_##_name = { \ + .attr = __ATTR(_name, 0400, nvdimm_stat_attr_show, NULL), \ + .stat_id = _stat_id, \ + } + +static NVDIMM_STAT_ATTR(media_reads, ND_DIMM_STAT_MEDIA_READS); +static NVDIMM_STAT_ATTR(media_writes, ND_DIMM_STAT_MEDIA_WRITES); +static NVDIMM_STAT_ATTR(read_requests, ND_DIMM_STAT_READ_REQUESTS); +static NVDIMM_STAT_ATTR(write_requests, ND_DIMM_STAT_WRITE_REQUESTS); +static NVDIMM_STAT_ATTR(total_media_reads, ND_DIMM_STAT_TOTAL_MEDIA_READS); +static NVDIMM_STAT_ATTR(total_media_writes, ND_DIMM_STAT_TOTAL_MEDIA_WRITES); +static NVDIMM_STAT_ATTR(total_read_requests, ND_DIMM_STAT_TOTAL_READ_REQUESTS); +static NVDIMM_STAT_ATTR(total_write_requests, ND_DIMM_STAT_TOTAL_WRITE_REQUESTS); + +static struct attribute *nvdimm_stats_attributes[] = { + &nvdimm_stat_attr_media_reads.attr.attr, + &nvdimm_stat_attr_media_writes.attr.attr, + &nvdimm_stat_attr_read_requests.attr.attr, + &nvdimm_stat_attr_write_requests.attr.attr, + &nvdimm_stat_attr_total_media_reads.attr.attr, + &nvdimm_stat_attr_total_media_writes.attr.attr, + &nvdimm_stat_attr_total_read_requests.attr.attr, + &nvdimm_stat_attr_total_write_requests.attr.attr, + NULL, +}; + +static const struct attribute_group nvdimm_stats_group = { + .name = "stats", + .attrs = nvdimm_stats_attributes, + .is_visible = nvdimm_stats_visible, +}; + static const struct attribute_group nvdimm_firmware_attribute_group = { .name = "firmware", .attrs = nvdimm_firmware_attributes, @@ -565,6 +673,7 @@ static const struct attribute_group *nvdimm_attribute_groups[] = { &nd_device_attribute_group, &nvdimm_attribute_group, &nvdimm_firmware_attribute_group, + &nvdimm_stats_group, NULL, }; diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h index 696b55556d4d..ea9e846ae245 100644 --- a/drivers/nvdimm/nd.h +++ b/drivers/nvdimm/nd.h @@ -223,6 +223,11 @@ enum nd_async_mode { ND_ASYNC, }; +struct nvdimm_stat_attr { + struct device_attribute attr; + u64 stat_id; +}; + int nd_integrity_init(struct gendisk *disk, unsigned long meta_size); void wait_nvdimm_bus_probe_idle(struct device *dev); void nd_device_register(struct device *dev); diff --git a/include/uapi/linux/ndctl.h b/include/uapi/linux/ndctl.h index 8cf1e4884fd5..81b76986b423 100644 --- a/include/uapi/linux/ndctl.h +++ b/include/uapi/linux/ndctl.h @@ -97,6 +97,31 @@ struct nd_cmd_clear_error { __u64 cleared; } __packed; +/* Various generic dimm stats that can be reported */ +enum { + ND_DIMM_STAT_INVALID = 0, + ND_DIMM_STAT_MEDIA_READS = 1, /* Media reads after power cycle */ + ND_DIMM_STAT_MEDIA_WRITES = 2, /* Media writes after power cycle */ + ND_DIMM_STAT_READ_REQUESTS = 3, /* Read requests after power cycle */ + ND_DIMM_STAT_WRITE_REQUESTS = 4, /* Write requests after power cycle */ + ND_DIMM_STAT_TOTAL_MEDIA_READS = 5, /* Total Media Reads */ + ND_DIMM_STAT_TOTAL_MEDIA_WRITES = 6, /* Total Media Writes */ + ND_DIMM_STAT_TOTAL_READ_REQUESTS = 7, /* Total Read Requests */ + ND_DIMM_STAT_TOTAL_WRITE_REQUESTS = 8, /* Total Write Requests */ + ND_DIMM_STAT_MAX = 8, +}; + +struct nd_cmd_get_dimm_stat { + /* See enum above for valid values */ + __u64 stat_id; + + /* Holds a single dimm stat value */ + union { + __s64 int_val; + char str_val[120]; + }; +} __packed; + enum { ND_CMD_IMPLEMENTED = 0, @@ -117,6 +142,7 @@ enum { ND_CMD_VENDOR_EFFECT_LOG = 8, ND_CMD_VENDOR = 9, ND_CMD_CALL = 10, + ND_CMD_GET_STAT = 11, }; enum { @@ -151,6 +177,7 @@ static inline const char *nvdimm_cmd_name(unsigned cmd) case ND_CMD_VENDOR_EFFECT_LOG: return "effect_log"; case ND_CMD_VENDOR: return "vendor"; case ND_CMD_CALL: return "cmd_call"; + case ND_CMD_GET_STAT: return "get_stat"; default: return "unknown"; } }
Implement support for exposing generic nvdimm statistics via newly introduced dimm-command ND_CMD_GET_STAT that can be handled by nvdimm command handler function and provide values for these statistics back to libnvdimm. Following generic nvdimm statistics are defined as an enumeration in 'uapi/ndctl.h': * "media_reads" : Number of media reads that have occurred since reboot. * "media_writes" : Number of media writes that have occurred since reboot. * "read_requests" : Number of read requests that have occurred since reboot. * "write_requests" : Number of write requests that have occurred since reboot. * "total_media_reads" : Total number of media reads that have occurred. * "total_media_writes" : Total number of media writes that have occurred. * "total_read_requests" : Total number of read requests that have occurred. * "total_write_requests" : Total number of write requests that have occurred. Apart from ND_CMD_GET_STAT ioctl these nvdimm statistics are also exposed via sysfs '<nvdimm-device>/stats' directory for easy user-space access like below: /sys/class/nd/ndctl0/device/nmem0/stats # tail -n +1 * ==> media_reads <== 252197707602 ==> media_writes <== 20684685172 ==> read_requests <== 658810924962 ==> write_requests <== 404464081574 In case a specific nvdimm-statistic is not supported than nvdimm command handler function can simply return an error (e.g -ENOENT) for request to read that nvdimm-statistic. The value for a specific nvdimm-stat is exchanged via newly introduced 'struct nd_cmd_get_dimm_stat' that hold a single statistics and a union of possible values types. Presently only '__s64' type of generic attributes are supported. These attributes are defined in 'ndvimm/dimm_devs.c' via a helper macro 'NVDIMM_STAT_ATTR'. Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com> --- drivers/nvdimm/bus.c | 6 ++ drivers/nvdimm/dimm_devs.c | 109 +++++++++++++++++++++++++++++++++++++ drivers/nvdimm/nd.h | 5 ++ include/uapi/linux/ndctl.h | 27 +++++++++ 4 files changed, 147 insertions(+)