[lustre-discuss] Fwd: RPCs in Flight are more than the max_rpcs_in_flight value

Md Hasanur Rashid mrashid2 at uncc.edu
Thu Oct 7 12:19:20 PDT 2021


Hello Everyone,

I am running the Filebench benchmark in my Lustre cluster. I set the
max_rpcs_in_flight value to be 1. Before executing and after executing, I
verified that the value of max_rpcs_in_flight is indeed 1. However, when I
check the rpc_stats, the stat shows a much higher value for RPCs in flight.
Following is the value shown for one OSC just for reference:

osc.hasanfs-OST0000-osc-ffff882fcf777000.rpc_stats=
snapshot_time:         1632483604.967291 (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:         1 100 100   |          0   0   0
2:         0   0 100   |          0   0   0
4:         0   0 100   |          0   0   0
8:         0   0 100   |          0   0   0
16:         0   0 100   |          0   0   0
32:         0   0 100   |          0   0   0
64:         0   0 100   |          0   0   0
128:         0   0 100   |          0   0   0
256:         0   0 100   |       9508 100 100

read write
rpcs in flight        rpcs   % cum % |       rpcs   % cum %
0:         0   0   0   |          0   0   0
1:         1 100 100   |         10   0   0
2:         0   0 100   |       9033  95  95
3:         0   0 100   |        465   4 100

read write
offset                rpcs   % cum % |       rpcs   % cum %
0:         1 100 100   |        725   7   7
1:         0   0 100   |          0   0   7
2:         0   0 100   |          0   0   7
4:         0   0 100   |          0   0   7
8:         0   0 100   |          0   0   7
16:         0   0 100   |          0   0   7
32:         0   0 100   |          0   0   7
64:         0   0 100   |          0   0   7
128:         0   0 100   |          0   0   7
256:         0   0 100   |        718   7  15
512:         0   0 100   |       1386  14  29
1024:         0   0 100   |       2205  23  52
2048:         0   0 100   |       1429  15  67
4096:         0   0 100   |       1103  11  79
8192:         0   0 100   |       1942  20 100

Can anyone please explain to me why the RPCs in flight shown in the
rpc_stats could be higher than the max_rpcs_in_flight?

Thanks,
Md. Hasanur Rashid
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