Hi All,
Please find attached v3 of the patch. It implements the changes requested by Greg. The statistics files aren't in a separate directory any more they're implemented directly as device attributes unless someone has objections to them being in a place like /sys/class/scsi_tape/*/.
There's also an ABI for file them in the patch for the testing directory. The kernel version is ?????? because I'm not sure if there will be more changes based on feedback - let me know if I should drop that from the patch than submit a separate patch requesting the file be created once I know the kernel version it makes it into. Is the ABI file named correctly as sysfs-class-scsi_tape?
I've dropped the sync file stuff as well - As much as I'd like consistent statistics Greg is right it won't hurt if they're not quite in sync. The patch including the additional ABI documentation is about two thirds of the original size.
Thanks
Shane
--
Signed-off-by: shane.seymour@xxxxxx
Tested-by: shane.seymour@xxxxxx
---
--- a/drivers/scsi/st.c 2015-01-11 14:46:00.243814755 -0600
+++ b/drivers/scsi/st.c 2015-02-08 16:50:51.368552780 -0600
@@ -476,10 +476,22 @@ static void st_scsi_execute_end(struct r
struct st_request *SRpnt = req->end_io_data;
struct scsi_tape *STp = SRpnt->stp;
struct bio *tmp;
+ u64 ticks;
STp->buffer->cmdstat.midlevel_result = SRpnt->result = req->errors;
STp->buffer->cmdstat.residual = req->resid_len;
+ if (STp->stats != NULL) {
+ ticks = get_jiffies_64();
+ STp->stats->in_flight--;
+ ticks -= STp->stats->stamp;
+ STp->stats->io_ticks += ticks;
+ if (req->cmd[0] == WRITE_6)
+ STp->stats->write_ticks += ticks;
+ else if (req->cmd[0] == READ_6)
+ STp->stats->read_ticks += ticks;
+ }
+
tmp = SRpnt->bio;
if (SRpnt->waiting)
complete(SRpnt->waiting);
@@ -496,6 +508,7 @@ static int st_scsi_execute(struct st_req
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 +529,20 @@ static int st_scsi_execute(struct st_req
}
}
+ if (STp->stats != NULL) {
+ if (cmd[0] == WRITE_6) {
+ STp->stats->write_cnt++;
+ STp->stats->write_byte_cnt += bufflen;
+ } else if (cmd[0] == READ_6) {
+ STp->stats->read_cnt++;
+ STp->stats->read_byte_cnt += bufflen;
+ } else {
+ STp->stats->other_cnt++;
+ }
+ STp->stats->stamp = get_jiffies_64();
+ STp->stats->in_flight++;
+ }
+
SRpnt->bio = req->bio;
req->cmd_len = COMMAND_SIZE(cmd[0]);
memset(req->cmd, 0, BLK_MAX_CDB);
@@ -4064,6 +4091,7 @@ out:
static int create_cdevs(struct scsi_tape *tape)
{
int mode, error;
+
for (mode = 0; mode < ST_NBR_MODES; ++mode) {
error = create_one_cdev(tape, mode, 0);
if (error)
@@ -4222,6 +4250,8 @@ static int st_probe(struct device *dev)
}
tpnt->index = error;
sprintf(disk->disk_name, "st%d", tpnt->index);
+/* Allocate stats structure */
+ tpnt->stats = kzalloc(sizeof(struct scsi_tape_stats), GFP_ATOMIC);
dev_set_drvdata(dev, tpnt);
@@ -4248,6 +4278,8 @@ out_put_queue:
blk_put_queue(disk->queue);
out_put_disk:
put_disk(disk);
+ if (tpnt->stats != NULL)
+ kfree(tpnt->stats);
kfree(tpnt);
out_buffer_free:
kfree(buffer);
@@ -4298,6 +4330,10 @@ static void scsi_tape_release(struct kre
disk->private_data = NULL;
put_disk(disk);
+ if (tpnt->stats != NULL) {
+ kfree(tpnt->stats);
+ tpnt->stats = NULL;
+ }
kfree(tpnt);
return;
}
@@ -4513,12 +4549,238 @@ options_show(struct device *dev, struct
}
static DEVICE_ATTR_RO(options);
+/* Support for tape stats */
+
+/**
+ * read_cnt_how - 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);
+ struct scsi_tape *STp = STm->tape;
+ struct scsi_tape_stats *STt;
+
+ if ((STp == 0) || (STp->stats == 0))
+ return -EINVAL;
+ STt = STp->stats;
+ if (STt == 0)
+ return -EINVAL;
+ return snprintf(buf, PAGE_SIZE, "%llu", STt->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);
+ struct scsi_tape *STp = STm->tape;
+ struct scsi_tape_stats *STt;
+
+ if ((STp == 0) || (STp->stats == 0))
+ return -EINVAL;
+ STt = STp->stats;
+ if (STt == 0)
+ return -EINVAL;
+ return snprintf(buf, PAGE_SIZE, "%llu", STt->read_byte_cnt);
+}
+DEVICE_ATTR_RO(read_byte_cnt);
+
+/**
+ * read_ms_show - return read ms - overall time spent waiting on reads in ms.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t read_ms_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+ struct scsi_tape *STp = STm->tape;
+ struct scsi_tape_stats *STt;
+
+ if ((STp == 0) || (STp->stats == 0))
+ return -EINVAL;
+ STt = STp->stats;
+ if (STt == 0)
+ return -EINVAL;
+ return snprintf(buf, PAGE_SIZE, "%u",
+ jiffies_to_msecs(STt->read_ticks));
+}
+DEVICE_ATTR_RO(read_ms);
+
+/**
+ * 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);
+ struct scsi_tape *STp = STm->tape;
+ struct scsi_tape_stats *STt;
+
+ if ((STp == 0) || (STp->stats == 0))
+ return -EINVAL;
+ STt = STp->stats;
+ if (STt == 0)
+ return -EINVAL;
+ return snprintf(buf, PAGE_SIZE, "%llu", STt->write_cnt);
+}
+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);
+ struct scsi_tape *STp = STm->tape;
+ struct scsi_tape_stats *STt;
+
+ if ((STp == 0) || (STp->stats == 0))
+ return -EINVAL;
+ STt = STp->stats;
+ if (STt == 0)
+ return -EINVAL;
+ return snprintf(buf, PAGE_SIZE, "%llu", STt->write_byte_cnt);
+}
+DEVICE_ATTR_RO(write_byte_cnt);
+
+/**
+ * write_ms_show - write ms - number of milliseconds since
+ * last open waiting on write requests to complete.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t write_ms_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+ struct scsi_tape *STp = STm->tape;
+ struct scsi_tape_stats *STt;
+
+ if ((STp == 0) || (STp->stats == 0))
+ return -EINVAL;
+ STt = STp->stats;
+ if (STt == 0)
+ return -EINVAL;
+ return snprintf(buf, PAGE_SIZE, "%u",
+ jiffies_to_msecs(STt->write_ticks));
+}
+DEVICE_ATTR_RO(write_ms);
+
+/**
+ * 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);
+ struct scsi_tape *STp = STm->tape;
+ struct scsi_tape_stats *STt;
+
+ if ((STp == 0) || (STp->stats == 0))
+ return -EINVAL;
+ STt = STp->stats;
+ if (STt == 0)
+ return -EINVAL;
+ return snprintf(buf, PAGE_SIZE, "%llu", STt->in_flight);
+}
+DEVICE_ATTR_RO(in_flight);
+
+/**
+ * io_ms_show - io wait ms - this is the number of ms spent
+ * waiting on all I/O to complete. This includes tape movement commands
+ * such as rewinding, seeking to end of file or tape, etc. Except in
+ * complex tape management programs these will be indirect commands issued
+ * by the driver - e.g. rewind on close.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t io_ms_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+ struct scsi_tape *STp = STm->tape;
+ struct scsi_tape_stats *STt;
+
+ if ((STp == 0) || (STp->stats == 0))
+ return -EINVAL;
+ STt = STp->stats;
+ if (STt == 0)
+ return -EINVAL;
+ return snprintf(buf, PAGE_SIZE, "%u",
+ jiffies_to_msecs(STt->io_ticks));
+}
+DEVICE_ATTR_RO(io_ms);
+
+/**
+ * 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);
+ struct scsi_tape *STp = STm->tape;
+ struct scsi_tape_stats *STt;
+
+ if ((STp == 0) || (STp->stats == 0))
+ return -EINVAL;
+ STt = STp->stats;
+ if (STt == 0)
+ return -EINVAL;
+ return snprintf(buf, PAGE_SIZE, "%llu", STt->other_cnt);
+}
+DEVICE_ATTR_RO(other_cnt);
+
static struct attribute *st_dev_attrs[] = {
&dev_attr_defined.attr,
&dev_attr_default_blksize.attr,
&dev_attr_default_density.attr,
&dev_attr_default_compression.attr,
&dev_attr_options.attr,
+ &dev_attr_read_cnt.attr,
+ &dev_attr_read_byte_cnt.attr,
+ &dev_attr_read_ms.attr,
+ &dev_attr_write_cnt.attr,
+ &dev_attr_write_byte_cnt.attr,
+ &dev_attr_write_ms.attr,
+ &dev_attr_in_flight.attr,
+ &dev_attr_io_ms.attr,
+ &dev_attr_other_cnt.attr,
NULL,
};
ATTRIBUTE_GROUPS(st_dev);
--- a/drivers/scsi/st.h 2015-01-11 14:46:00.243814755 -0600
+++ b/drivers/scsi/st.h 2015-02-08 14:04:43.248288113 -0600
@@ -92,6 +92,21 @@ struct st_partstat {
int drv_file;
};
+/* Tape statistics */
+struct scsi_tape_stats {
+ u64 read_byte_cnt; /* bytes read */
+ u64 write_byte_cnt; /* bytes written */
+ u64 in_flight; /* Number of I/Os in flight */
+ u64 read_cnt; /* Count of read requests */
+ u64 write_cnt; /* Count of write requests */
+ u64 other_cnt; /* Count of other requests either implicit
+ or from user space via ioctl. */
+ u64 read_ticks; /* Ticks spent completing read requests */
+ u64 write_ticks; /* Ticks spent completing write requests */
+ u64 io_ticks; /* Ticks spent doing any I/O */
+ u64 stamp; /* holds time request was queued */
+};
+
#define ST_NBR_PARTITIONS 4
/* The tape drive descriptor */
@@ -171,6 +186,7 @@ struct scsi_tape {
#endif
struct gendisk *disk;
struct kref kref;
+ struct scsi_tape_stats *stats;
};
/* Bit masks for use_pf */
--- a/Documentation/scsi/st.txt 2015-01-11 14:45:56.235815028 -0600
+++ b/Documentation/scsi/st.txt 2015-02-08 15:43:58.115826107 -0600
@@ -151,6 +151,55 @@ A link named 'tape' is made from the SCS
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>/
+ 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_ms - The amount of time spent waiting (in milliseconds) 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_ms - The amount of time (in milliseconds) 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_ms - The amount of time (in milliseconds) spent waiting for write
+ requests to complete.
+
+Note: The count statistics are incrememented at the start of an I/O but the
+time they take to complete is not added to the statistics until they complete.
+
+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. They should
+however be close and when used to calculate averages or throughput it
+shouldn't matter.
+
+
BSD AND SYS V SEMANTICS
The user can choose between these two behaviours of the tape driver by
--- a/Documentation/ABI/testing/sysfs-class-scsi_tape 1969-12-31 18:00:00.000000000 -0600
+++ b/Documentation/ABI/testing/sysfs-class-scsi_tape 2015-02-08 16:56:50.251528338 -0600
@@ -0,0 +1,97 @@
+What: /sys/class/scsi_tape/*/in_flight
+Date: Feb 2015
+KernelVersion: ??????
+Contact: Shane Seymour <shane.seymour@xxxxxx>
+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/*/io_ms
+Date: Feb 2015
+KernelVersion: ??????
+Contact: Shane Seymour <shane.seymour@xxxxxx>
+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.
+
+ To determine the amount of time spent waiting for other I/O
+ to complete subtract read_ms and write_ms from this value.
+Users:
+
+
+What: /sys/class/scsi_tape/*/other_cnt
+Date: Feb 2015
+KernelVersion: ??????
+Contact: Shane Seymour <shane.seymour@xxxxxx>
+Description:
+ The number of I/O requests issued to the tape drive other
+ than SCSI read/write requests.
+Users:
+
+
+What: /sys/class/scsi_tape/*/read_byte_cnt
+Date: Feb 2015
+KernelVersion: ??????
+Contact: Shane Seymour <shane.seymour@xxxxxx>
+Description:
+ Shows the total number of bytes read from the tape drive.
+ This value is presented in bytes because tape drives support
+ variable length block sizes.
+Users:
+
+
+What: /sys/class/scsi_tape/*/read_cnt
+Date: Feb 2015
+KernelVersion: ??????
+Contact: Shane Seymour <shane.seymour@xxxxxx>
+Description:
+ Shows the total number of read requests issued to the tape
+ drive.
+Users:
+
+
+What: /sys/class/scsi_tape/*/read_ms
+Date: Feb 2015
+KernelVersion: ??????
+Contact: Shane Seymour <shane.seymour@xxxxxx>
+Description:
+ Shows the total amount of time in milliseconds waiting for
+ read I/O requests to complete.
+Users:
+
+
+What: /sys/class/scsi_tape/*/write_byte_cnt
+Date: Feb 2015
+KernelVersion: ??????
+Contact: Shane Seymour <shane.seymour@xxxxxx>
+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/*/write_cnt
+Date: Feb 2015
+KernelVersion: ??????
+Contact: Shane Seymour <shane.seymour@xxxxxx>
+Description:
+ Shows the total number of write requests issued to the tape
+ drive.
+Users:
+
+
+What: /sys/class/scsi_tape/*/write_ms
+Date: Feb 2015
+KernelVersion: ??????
+Contact: Shane Seymour <shane.seymour@xxxxxx>
+Description:
+ Shows the total amount of time in milliseconds waiting for
+ write I/O requests to complete.
+Users:
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