-- Ray
Hi Ray,
Here is the description of the different latencies under filestore perf counters.
Journal_latency :
----------------------
This is the latency of putting the ops in journal. Write is acknowledged after that (well a bit after that, there is one context switch after this).
commitcycle_latency:
--------------------------
Filestore backend while carrying out transaction, do a buffered write. In a separate thread it does call syncfs() to persist the data to the disk and update the persistent commit number in a separate file. This thread runs by default 5 sec interval.
This latency measures the time taken to carry out this job after the timer expires i.e the actual persisting cycle.
apply_latency:
----------------
This is the entire latency till the transaction finishes i.e journal write + transaction time. It will do a buffer write here.
queue_transaction_latency_avg:
----------------------------------------
This is the latency of putting the op in the journal queue. This will give you an idea how much throttling is going on at the first place. This depends on the following two parameters if you are using XFS.
filestore_queue_max_ops
filestore_queue_max_bytes
All the latency numbers are represented by avgcount(number of ops within this range) and the sum (which is total latency in second). Sum/avgcount will give you an idea the latency per op.
Hope this is helpful,
Thanks & Regards
Somnath
From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of Ray Sun
Sent: Sunday, July 05, 2015 7:28 AM
To: ceph-users@xxxxxxxxxxxxxx
Subject: Meanning of ceph perf dump
Cephers,
Is there any documents or code definition to explain ceph perf dump? I am a little confusing about the output, for example, under filestore, there's journal_latency and apply_latency and each of them has avgcount and sum. I am not quite sure what's the unit and meaning of the numbers? How can I use these numbers to tuning my ceph cluster. Thanks a lot.
"filestore": {
"journal_queue_max_ops": 300,
"journal_queue_ops": 0,
"journal_ops": 35893,
"journal_queue_max_bytes": 33554432,
"journal_queue_bytes": 0,
"journal_bytes": 20579009432,
"journal_latency": {
"avgcount": 35893,
"sum": 1213.560761279
},
"journal_wr": 34228,
"journal_wr_bytes": {
"avgcount": 34228,
"sum": 20657713152
},
"journal_full": 0,
"committing": 0,
"commitcycle": 3207,
"commitcycle_interval": {
"avgcount": 3207,
"sum": 16157.379852152
},
"commitcycle_latency": {
"avgcount": 3207,
"sum": 121.892109010
},
"op_queue_max_ops": 50,
"op_queue_ops": 0,
"ops": 35893,
"op_queue_max_bytes": 104857600,
"op_queue_bytes": 0,
"bytes": 20578506930,
"apply_latency": {
"avgcount": 35893,
"sum": 1327.974596287
},
"queue_transaction_latency_avg": {
"avgcount": 35893,
"sum": 0.025993727
}
},
Best Regards
-- Ray
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