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>
diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
index f3eee0f..b6486b5 100644
--- a/drivers/scsi/st.h
+++ b/drivers/scsi/st.h
@@ -92,6 +92,27 @@
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 @@
#endif
struct gendisk *disk;
struct kref kref;
+ struct scsi_tape_stats *stats;
};
/* Bit masks for use_pf */
