Hello,
I pulled the latest revision of this patch and tested it. I can vouch
for it working as expected with out any obvious impact to the existing
st driver
Is there any way we can move this along.
Thanks
Tested-by:Laurence Oberman <loberman@xxxxxxxxxx>
On Thu, Feb 12, 2015 at 6:15 AM, Seymour, Shane M <shane.seymour@xxxxxx> wrote:
> The following patch exposes statistics for the st driver via sysfs.
> There is a need for companies with large numbers of tape drives
> numbering in the tens of thousands to track the performance of
> those tape drives (e.g. when a backup exceeds its window). The
> statistics provided should allow the calculation of throughput,
> average block sizes for read and write, and time spent waiting
> for I/O to complete or doing tape movement.
>
> Signed-off-by: Shane Seymour <shane.seymour@xxxxxx>
> Tested-by: Shane Seymour <shane.seymour@xxxxxx>
> ---
> - Removed comment
> - Found an issue where read and write sizes were over reported
> (fixed) In all the test cases I have the stats now report what I
> expect to be the correct value. Some of the values to be used
> with statistics are now stored in temporary variables and used
> to calculate the stats when the I/O ends. Separated out the
> timestamp into 3 since I found it was possible for other tape
> I/O to happen during writes updating the stamp value causing
> the time tracked to be wrong.
> - Moved the end statistics into a separate function because it
> had made the function that it was in too large.
> - Added a new statistic - A count of the number of times we had
> a residual greater than 0.
> --- a/drivers/scsi/st.c 2015-01-11 14:46:00.243814755 -0600
> +++ b/drivers/scsi/st.c 2015-02-11 22:37:01.382243090 -0600
> @@ -471,6 +471,47 @@ static void st_release_request(struct st
> kfree(streq);
> }
>
> +static void st_do_stats(struct scsi_tape *STp, struct request *req)
> +{
> + u64 ticks;
> +
> + ticks = get_jiffies_64();
> + STp->stats->in_flight--;
> + if (req->cmd[0] == WRITE_6) {
> + ticks -= STp->stats->write_stamp;
> + STp->stats->write_ticks += ticks;
> + STp->stats->io_ticks += ticks;
> + STp->stats->write_cnt++;
> + if (req->errors) {
> + STp->stats->write_byte_cnt +=
> + STp->stats->last_write_size -
> + STp->buffer->cmdstat.residual;
> + if (STp->buffer->cmdstat.residual > 0)
> + STp->stats->resid_cnt++;
> + } else
> + STp->stats->write_byte_cnt +=
> + STp->stats->last_write_size;
> + } else if (req->cmd[0] == READ_6) {
> + ticks -= STp->stats->read_stamp;
> + STp->stats->read_ticks += ticks;
> + STp->stats->io_ticks += ticks;
> + STp->stats->read_cnt++;
> + if (req->errors)
> + STp->stats->read_byte_cnt +=
> + STp->stats->last_read_size -
> + STp->buffer->cmdstat.residual;
> + if (STp->buffer->cmdstat.residual > 0)
> + STp->stats->resid_cnt++;
> + else
> + STp->stats->read_byte_cnt +=
> + STp->stats->last_read_size;
> + } else {
> + ticks -= STp->stats->other_stamp;
> + STp->stats->io_ticks += ticks;
> + STp->stats->other_cnt++;
> + }
> +}
> +
> 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 r
> 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_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 +560,17 @@ static int st_scsi_execute(struct st_req
> }
> }
>
> + if (cmd[0] == WRITE_6) {
> + STp->stats->last_write_size = bufflen;
> + STp->stats->write_stamp = get_jiffies_64();
> + } else if (cmd[0] == READ_6) {
> + STp->stats->last_read_size = bufflen;
> + STp->stats->read_stamp = get_jiffies_64();
> + } else {
> + STp->stats->other_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);
> @@ -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 kre
>
> disk->private_data = NULL;
> put_disk(disk);
> + kfree(tpnt->stats);
> kfree(tpnt);
> return;
> }
> @@ -4513,6 +4577,178 @@ options_show(struct device *dev, struct
> }
> 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, "%llu", 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, "%llu", STm->tape->stats->read_byte_cnt);
> +}
> +static 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);
> +
> + return sprintf(buf, "%u",
> + jiffies_to_msecs(STm->tape->stats->read_ticks));
> +}
> +static 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);
> +
> + return sprintf(buf, "%llu", 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, "%llu",
> + STm->tape->stats->write_byte_cnt);
> +}
> +static 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);
> +
> + return sprintf(buf, "%u",
> + jiffies_to_msecs(STm->tape->stats->write_ticks));
> +}
> +static 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);
> +
> + return sprintf(buf, "%llu", STm->tape->stats->in_flight);
> +}
> +static 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);
> +
> + return sprintf(buf, "%u",
> + jiffies_to_msecs(STm->tape->stats->io_ticks));
> +}
> +static 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);
> +
> + return sprintf(buf, "%llu", 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 someon 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, "%llu", 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 +4757,35 @@ 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_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,
> + &dev_attr_resid_cnt.attr,
> + NULL,
> +};
> +
> +static struct attribute_group stats_group = {
> + .name = "statistics",
> + .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,
> --- a/drivers/scsi/st.h 2015-01-11 14:46:00.243814755 -0600
> +++ b/drivers/scsi/st.h 2015-02-11 22:12:50.442341908 -0600
> @@ -92,6 +92,26 @@ 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 resid_cnt; /* Count of resid_len > 0 */
> + u64 read_stamp; /* holds time request was queued */
> + u64 write_stamp; /* holds time request was queued */
> + u64 other_stamp; /* holds time request was queued */
> + u32 last_read_size; /* Number of bytes issued for last read */
> + u32 last_write_size; /* Number of bytes issued for last write */
> +};
> +
> #define ST_NBR_PARTITIONS 4
>
> /* The tape drive descriptor */
> @@ -171,6 +191,7 @@ 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 2015-02-11 22:17:17.588323714 -0600
> @@ -151,6 +151,59 @@ 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>/statistics
> + 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.
> +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 incremnented 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. 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 2015-02-11 22:35:28.068249446 -0600
> @@ -0,0 +1,109 @@
> +What: /sys/class/scsi_tape/*/statistics/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/*/statistics/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/*/statistics/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/*/statistics/read_byte_cnt
> +Date: Feb 2015
> +KernelVersion: ??????
> +Contact: Shane Seymour <shane.seymour@xxxxxx>
> +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/*/statistics/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/*/statistics/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/*/statistics/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/*/statistics/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/*/statistics/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:
> +
> +
> +What: /sys/class/scsi_tape/*/statistics/resid_cnt
> +Date: Feb 2015
> +KernelVersion: ??????
> +Contact: Shane Seymour <shane.seymour@xxxxxx>
> +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:
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