Lustre 1.6 Operations Manual

20.2.2 Watching the Client RPC Stream
In the same directory is a file that gives a histogram of the make-up of previous
RPCs.
# cat /proc/fs/lustre/osc/spfs-OST0000-osc-c45f9c00/rpc_stats
snapshot_time:
1174867307.156604 (secs.usecs)
read RPCs in flight: 0
write RPCs in flight: 0
pending write pages: 0
pending read pages: 0
read
write
pages per rpc rpcs % cum % | rpcs % cum %
1: 0 0 0 | 0 0 0
read
write
rpcs in flight rpcs % cum % | rpcs % cum %
0: 0 0 0 | 0 0 0
read
write
offset rpcs % cum % | rpcs % cum %
0: 0 0 0 | 0 0 0
RPCs in flight
This represents the number of RPCs that are issued by the OSC but are not complete
at the time of the snapshot. It should always be less than or equal to
max_rpcs_in_flight.
pending {read,write} pages
These fields show the number of pages that have been queued for I/O in the OSC.
other RPCs in flight when a new RPC is sent
When an RPC is sent, it records the number of other RPCs that were pending in this
table. When the first RPC is sent, the 0: row will be incremented. If the first RPC is
sent while another is pending the 1: row will be incremented and so on. The number
of RPCs that are pending as each RPC *completes* is not tabulated. This table is a
good way of visualizing the concurrency of the RPC stream. Ideally you will see a
large clump around the max_rpcs_in_flight value which shows that the network
is being kept busy.
pages in each RPC
As an RPC is sent, the number of pages it is made of is recorded in order in this
table. A single page RPC increments the 0: row, 128 pages the 7: row and so on.
These histograms can be cleared by writing any value into the rpc_stats file.
20-14 Lustre 1.6 Operations Manual • September 2008