[RFC][PATCH 1/2] libnvdimm: Introduce ND_CMD_GET_STAT to retrieve nvdimm statistics
Dan Williams
dan.j.williams at intel.com
Tue Dec 8 11:54:21 AEDT 2020
[ add perf maintainers ]
On Sun, Nov 8, 2020 at 1:16 PM Vaibhav Jain <vaibhav at 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 at 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?
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