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authorSeymour, Shane M <shane.seymour@hp.com>2015-05-06 01:37:20 +0000
committerJames Bottomley <JBottomley@Odin.com>2015-06-02 08:03:25 -0700
commit05545c92db9637318a98d3d59d400beb819decc7 (patch)
tree56c911568dd7dd6507aac24f7c8c90b657f7bda0
parentba929992522b6d1f866b7021bc50da66f8fdd743 (diff)
downloadlinux-linaro-stable-05545c92db9637318a98d3d59d400beb819decc7.tar.gz
st: implement tape statistics
This patch implements tape statistics in the st module via sysfs. Current no statistics are available for tape I/O and there is no easy way to reuse the block layer statistics for tape as tape is a character device and does not have perform I/O in sector sized chunks (the size of the data written to tape can change). For tapes we also need extra stats related to things like tape movement (via other I/O). There have been multiple end users requesting statistics including AT&T (and some HP customers who have not given permission to be named). It is impossible for them to investigate any issues related to tape performance in a non-invasive way. [jejb: eliminate PRId64] Signed-off-by: Shane Seymour <shane.seymour@hp.com> Tested-by: Shane Seymour <shane.seymour@hp.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: James Bottomley <JBottomley@Odin.com>
-rw-r--r--Documentation/ABI/testing/sysfs-class-scsi_tape109
-rw-r--r--Documentation/scsi/st.txt59
-rw-r--r--drivers/scsi/st.c272
-rw-r--r--drivers/scsi/st.h22
4 files changed, 461 insertions, 1 deletions
diff --git a/Documentation/ABI/testing/sysfs-class-scsi_tape b/Documentation/ABI/testing/sysfs-class-scsi_tape
new file mode 100644
index 000000000000..9be398b87ee9
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-scsi_tape
@@ -0,0 +1,109 @@
+What: /sys/class/scsi_tape/*/stats/in_flight
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Show the number of I/Os currently in-flight between the st
+ module and the SCSI mid-layer.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/io_ns
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total amount of time spent waiting for all I/O
+ to and from the tape drive to complete. This includes all
+ reads, writes, and other SCSI commands issued to the tape
+ drive. An example of other SCSI commands would be tape
+ movement such as a rewind when a rewind tape device is
+ closed. This item is measured in nanoseconds.
+
+ To determine the amount of time spent waiting for other I/O
+ to complete subtract read_ns and write_ns from this value.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/other_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ The number of I/O requests issued to the tape drive other
+ than SCSI read/write requests.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/read_byte_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total number of bytes requested from the tape drive.
+ This value is presented in bytes because tape drives support
+ variable length block sizes.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/read_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total number of read requests issued to the tape
+ drive.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/read_ns
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total amount of time in nanoseconds waiting for
+ read I/O requests to complete.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/write_byte_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total number of bytes written to the tape drive.
+ This value is presented in bytes because tape drives support
+ variable length block sizes.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/write_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total number of write requests issued to the tape
+ drive.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/write_ms
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total amount of time in nanoseconds waiting for
+ write I/O requests to complete.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/resid_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the number of times we found that a residual >0
+ was found when the SCSI midlayer indicated that there was
+ an error. For reads this may be a case of someone issuing
+ reads greater than the block size.
+Users:
diff --git a/Documentation/scsi/st.txt b/Documentation/scsi/st.txt
index 0d5bdb153d3b..f29fa550665a 100644
--- a/Documentation/scsi/st.txt
+++ b/Documentation/scsi/st.txt
@@ -151,6 +151,65 @@ A link named 'tape' is made from the SCSI device directory to the class
directory corresponding to the mode 0 auto-rewind device (e.g., st0).
+SYSFS AND STATISTICS FOR TAPE DEVICES
+
+The st driver maintains statistics for tape drives inside the sysfs filesystem.
+The following method can be used to locate the statistics that are
+available (assuming that sysfs is mounted at /sys):
+
+1. Use opendir(3) on the directory /sys/class/scsi_tape
+2. Use readdir(3) to read the directory contents
+3. Use regcomp(3)/regexec(3) to match directory entries to the extended
+ regular expression "^st[0-9]+$"
+4. Access the statistics from the /sys/class/scsi_tape/<match>/stats
+ directory (where <match> is a directory entry from /sys/class/scsi_tape
+ that matched the extended regular expression)
+
+The reason for using this approach is that all the character devices
+pointing to the same tape drive use the same statistics. That means
+that st0 would have the same statistics as nst0.
+
+The directory contains the following statistics files:
+
+1. in_flight - The number of I/Os currently outstanding to this device.
+2. io_ns - The amount of time spent waiting (in nanoseconds) for all I/O
+ to complete (including read and write). This includes tape movement
+ commands such as seeking between file or set marks and implicit tape
+ movement such as when rewind on close tape devices are used.
+3. other_cnt - The number of I/Os issued to the tape drive other than read or
+ write commands. The time taken to complete these commands uses the
+ following calculation io_ms-read_ms-write_ms.
+4. read_byte_cnt - The number of bytes read from the tape drive.
+5. read_cnt - The number of read requests issued to the tape drive.
+6. read_ns - The amount of time (in nanoseconds) spent waiting for read
+ requests to complete.
+7. write_byte_cnt - The number of bytes written to the tape drive.
+8. write_cnt - The number of write requests issued to the tape drive.
+9. write_ns - The amount of time (in nanoseconds) spent waiting for write
+ requests to complete.
+10. resid_cnt - The number of times during a read or write we found
+ the residual amount to be non-zero. This should mean that a program
+ is issuing a read larger thean the block size on tape. For write
+ not all data made it to tape.
+
+Note: The in_flight value is incremented when an I/O starts the I/O
+itself is not added to the statistics until it completes.
+
+The total of read_cnt, write_cnt, and other_cnt may not total to the same
+value as iodone_cnt at the device level. The tape statistics only count
+I/O issued via the st module.
+
+When read the statistics may not be temporally consistent while I/O is in
+progress. The individual values are read and written to atomically however
+when reading them back via sysfs they may be in the process of being
+updated when starting an I/O or when it is completed.
+
+The value shown in in_flight is incremented before any statstics are
+updated and decremented when an I/O completes after updating statistics.
+The value of in_flight is 0 when there are no I/Os outstanding that are
+issued by the st driver. Tape statistics do not take into account any
+I/O performed via the sg device.
+
BSD AND SYS V SEMANTICS
The user can choose between these two behaviours of the tape driver by
diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index 9a1c34205254..3f25b8fa921d 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -471,6 +471,47 @@ static void st_release_request(struct st_request *streq)
kfree(streq);
}
+static void st_do_stats(struct scsi_tape *STp, struct request *req)
+{
+ ktime_t now;
+
+ now = ktime_get();
+ if (req->cmd[0] == WRITE_6) {
+ now = ktime_sub(now, STp->stats->write_time);
+ atomic64_add(ktime_to_ns(now), &STp->stats->tot_write_time);
+ atomic64_add(ktime_to_ns(now), &STp->stats->tot_io_time);
+ atomic64_inc(&STp->stats->write_cnt);
+ if (req->errors) {
+ atomic64_add(atomic_read(&STp->stats->last_write_size)
+ - STp->buffer->cmdstat.residual,
+ &STp->stats->write_byte_cnt);
+ if (STp->buffer->cmdstat.residual > 0)
+ atomic64_inc(&STp->stats->resid_cnt);
+ } else
+ atomic64_add(atomic_read(&STp->stats->last_write_size),
+ &STp->stats->write_byte_cnt);
+ } else if (req->cmd[0] == READ_6) {
+ now = ktime_sub(now, STp->stats->read_time);
+ atomic64_add(ktime_to_ns(now), &STp->stats->tot_read_time);
+ atomic64_add(ktime_to_ns(now), &STp->stats->tot_io_time);
+ atomic64_inc(&STp->stats->read_cnt);
+ if (req->errors) {
+ atomic64_add(atomic_read(&STp->stats->last_read_size)
+ - STp->buffer->cmdstat.residual,
+ &STp->stats->read_byte_cnt);
+ if (STp->buffer->cmdstat.residual > 0)
+ atomic64_inc(&STp->stats->resid_cnt);
+ } else
+ atomic64_add(atomic_read(&STp->stats->last_read_size),
+ &STp->stats->read_byte_cnt);
+ } else {
+ now = ktime_sub(now, STp->stats->other_time);
+ atomic64_add(ktime_to_ns(now), &STp->stats->tot_io_time);
+ atomic64_inc(&STp->stats->other_cnt);
+ }
+ atomic64_dec(&STp->stats->in_flight);
+}
+
static void st_scsi_execute_end(struct request *req, int uptodate)
{
struct st_request *SRpnt = req->end_io_data;
@@ -480,6 +521,8 @@ static void st_scsi_execute_end(struct request *req, int uptodate)
STp->buffer->cmdstat.midlevel_result = SRpnt->result = req->errors;
STp->buffer->cmdstat.residual = req->resid_len;
+ st_do_stats(STp, req);
+
tmp = SRpnt->bio;
if (SRpnt->waiting)
complete(SRpnt->waiting);
@@ -496,6 +539,7 @@ static int st_scsi_execute(struct st_request *SRpnt, const unsigned char *cmd,
struct rq_map_data *mdata = &SRpnt->stp->buffer->map_data;
int err = 0;
int write = (data_direction == DMA_TO_DEVICE);
+ struct scsi_tape *STp = SRpnt->stp;
req = blk_get_request(SRpnt->stp->device->request_queue, write,
GFP_KERNEL);
@@ -516,6 +560,17 @@ static int st_scsi_execute(struct st_request *SRpnt, const unsigned char *cmd,
}
}
+ atomic64_inc(&STp->stats->in_flight);
+ if (cmd[0] == WRITE_6) {
+ atomic_set(&STp->stats->last_write_size, bufflen);
+ STp->stats->write_time = ktime_get();
+ } else if (cmd[0] == READ_6) {
+ atomic_set(&STp->stats->last_read_size, bufflen);
+ STp->stats->read_time = ktime_get();
+ } else {
+ STp->stats->other_time = ktime_get();
+ }
+
SRpnt->bio = req->bio;
req->cmd_len = COMMAND_SIZE(cmd[0]);
memset(req->cmd, 0, BLK_MAX_CDB);
@@ -4222,6 +4277,12 @@ static int st_probe(struct device *dev)
}
tpnt->index = error;
sprintf(disk->disk_name, "st%d", tpnt->index);
+ tpnt->stats = kzalloc(sizeof(struct scsi_tape_stats), GFP_KERNEL);
+ if (tpnt->stats == NULL) {
+ sdev_printk(KERN_ERR, SDp,
+ "st: Can't allocate statistics.\n");
+ goto out_idr_remove;
+ }
dev_set_drvdata(dev, tpnt);
@@ -4241,6 +4302,8 @@ static int st_probe(struct device *dev)
out_remove_devs:
remove_cdevs(tpnt);
+ kfree(tpnt->stats);
+out_idr_remove:
spin_lock(&st_index_lock);
idr_remove(&st_index_idr, tpnt->index);
spin_unlock(&st_index_lock);
@@ -4298,6 +4361,7 @@ static void scsi_tape_release(struct kref *kref)
disk->private_data = NULL;
put_disk(disk);
+ kfree(tpnt->stats);
kfree(tpnt);
return;
}
@@ -4513,6 +4577,184 @@ options_show(struct device *dev, struct device_attribute *attr, char *buf)
}
static DEVICE_ATTR_RO(options);
+/* Support for tape stats */
+
+/**
+ * read_cnt_show - return read count - count of reads made from tape drive
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t read_cnt_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%lld",
+ (long long)atomic64_read(&STm->tape->stats->read_cnt));
+}
+static DEVICE_ATTR_RO(read_cnt);
+
+/**
+ * read_byte_cnt_show - return read byte count - tape drives
+ * may use blocks less than 512 bytes this gives the raw byte count of
+ * of data read from the tape drive.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t read_byte_cnt_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%lld",
+ (long long)atomic64_read(&STm->tape->stats->read_byte_cnt));
+}
+static DEVICE_ATTR_RO(read_byte_cnt);
+
+/**
+ * read_us_show - return read us - overall time spent waiting on reads in ns.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t read_ns_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%lld",
+ (long long)atomic64_read(&STm->tape->stats->tot_read_time));
+}
+static DEVICE_ATTR_RO(read_ns);
+
+/**
+ * write_cnt_show - write count - number of user calls
+ * to write(2) that have written data to tape.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t write_cnt_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%lld",
+ (long long)atomic64_read(&STm->tape->stats->write_cnt));
+}
+static DEVICE_ATTR_RO(write_cnt);
+
+/**
+ * write_byte_cnt_show - write byte count - raw count of
+ * bytes written to tape.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t write_byte_cnt_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%lld",
+ (long long)atomic64_read(&STm->tape->stats->write_byte_cnt));
+}
+static DEVICE_ATTR_RO(write_byte_cnt);
+
+/**
+ * write_ns_show - write ns - number of nanoseconds waiting on write
+ * requests to complete.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t write_ns_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%lld",
+ (long long)atomic64_read(&STm->tape->stats->tot_write_time));
+}
+static DEVICE_ATTR_RO(write_ns);
+
+/**
+ * in_flight_show - number of I/Os currently in flight -
+ * in most cases this will be either 0 or 1. It may be higher if someone
+ * has also issued other SCSI commands such as via an ioctl.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t in_flight_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%lld",
+ (long long)atomic64_read(&STm->tape->stats->in_flight));
+}
+static DEVICE_ATTR_RO(in_flight);
+
+/**
+ * io_ns_show - io wait ns - this is the number of ns spent
+ * waiting on all I/O to complete. This includes tape movement commands
+ * such as rewinding, seeking to end of file or tape, it also includes
+ * read and write. To determine the time spent on tape movement
+ * subtract the read and write ns from this value.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t io_ns_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%lld",
+ (long long)atomic64_read(&STm->tape->stats->tot_io_time));
+}
+static DEVICE_ATTR_RO(io_ns);
+
+/**
+ * other_cnt_show - other io count - this is the number of
+ * I/O requests other than read and write requests.
+ * Typically these are tape movement requests but will include driver
+ * tape movement. This includes only requests issued by the st driver.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t other_cnt_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%lld",
+ (long long)atomic64_read(&STm->tape->stats->other_cnt));
+}
+static DEVICE_ATTR_RO(other_cnt);
+
+/**
+ * resid_cnt_show - A count of the number of times we get a residual
+ * count - this should indicate someone issuing reads larger than the
+ * block size on tape.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t resid_cnt_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%lld",
+ (long long)atomic64_read(&STm->tape->stats->resid_cnt));
+}
+static DEVICE_ATTR_RO(resid_cnt);
+
static struct attribute *st_dev_attrs[] = {
&dev_attr_defined.attr,
&dev_attr_default_blksize.attr,
@@ -4521,7 +4763,35 @@ static struct attribute *st_dev_attrs[] = {
&dev_attr_options.attr,
NULL,
};
-ATTRIBUTE_GROUPS(st_dev);
+
+static struct attribute *st_stats_attrs[] = {
+ &dev_attr_read_cnt.attr,
+ &dev_attr_read_byte_cnt.attr,
+ &dev_attr_read_ns.attr,
+ &dev_attr_write_cnt.attr,
+ &dev_attr_write_byte_cnt.attr,
+ &dev_attr_write_ns.attr,
+ &dev_attr_in_flight.attr,
+ &dev_attr_io_ns.attr,
+ &dev_attr_other_cnt.attr,
+ &dev_attr_resid_cnt.attr,
+ NULL,
+};
+
+static struct attribute_group stats_group = {
+ .name = "stats",
+ .attrs = st_stats_attrs,
+};
+
+static struct attribute_group st_group = {
+ .attrs = st_dev_attrs,
+};
+
+static const struct attribute_group *st_dev_groups[] = {
+ &st_group,
+ &stats_group,
+ NULL,
+};
/* The following functions may be useful for a larger audience. */
static int sgl_map_user_pages(struct st_buffer *STbp,
diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
index f3eee0f9f40c..b6486b5d8681 100644
--- a/drivers/scsi/st.h
+++ b/drivers/scsi/st.h
@@ -92,6 +92,27 @@ struct st_partstat {
int drv_file;
};
+/* Tape statistics */
+struct scsi_tape_stats {
+ atomic64_t read_byte_cnt; /* bytes read */
+ atomic64_t write_byte_cnt; /* bytes written */
+ atomic64_t in_flight; /* Number of I/Os in flight */
+ atomic64_t read_cnt; /* Count of read requests */
+ atomic64_t write_cnt; /* Count of write requests */
+ atomic64_t other_cnt; /* Count of other requests either
+ * implicit or from user space
+ * ioctl. */
+ atomic64_t resid_cnt; /* Count of resid_len > 0 */
+ atomic64_t tot_read_time; /* ktime spent completing reads */
+ atomic64_t tot_write_time; /* ktime spent completing writes */
+ atomic64_t tot_io_time; /* ktime spent doing any I/O */
+ ktime_t read_time; /* holds ktime request was queued */
+ ktime_t write_time; /* holds ktime request was queued */
+ ktime_t other_time; /* holds ktime request was queued */
+ atomic_t last_read_size; /* Number of bytes issued for last read */
+ atomic_t last_write_size; /* Number of bytes issued for last write */
+};
+
#define ST_NBR_PARTITIONS 4
/* The tape drive descriptor */
@@ -171,6 +192,7 @@ struct scsi_tape {
#endif
struct gendisk *disk;
struct kref kref;
+ struct scsi_tape_stats *stats;
};
/* Bit masks for use_pf */