[SERVER-17251] with journal turned off journal compression option seems to affect throughput Created: 11/Feb/15  Updated: 08/Apr/15  Resolved: 22/Feb/15

Status: Closed
Project: Core Server
Component/s: WiredTiger
Affects Version/s: 3.0.0-rc8
Fix Version/s: None

Type: Bug Priority: Major - P3
Reporter: Asya Kamsky Assignee: Asya Kamsky
Resolution: Cannot Reproduce Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Backwards Compatibility: Fully Compatible
Operating System: ALL
Participants:

 Description   

Trying to test how much journal compression affects throughput with journal turned on, I inadvertently timed multiple runs with journal turned off both with and without journal compression type specified as none (vs snappy).

Surprisingly I see a consistent difference, where none gives better performance. But journal compression setting should be irrelevant if journaling is disabled.



 Comments   
Comment by Asya Kamsky [ 22/Feb/15 ]

seems to have been a statistical fluke, cannot reproduce.

Comment by Adam Comerford [ 11/Feb/15 ]

Did some more testing, cut the threads in half on the client, added zlib for a couple of runs just to be sure. Pretty consistent, not seeing a differential now with my testing - entirely possible the variance I saw last night was CPU related as well (was running everything on the same host at that point):

4 threads, journal disabled, journal compressor = snappy

run 1: 318.321
run 2: 321.376

4 threads, journal disabled, journal compressor = none

run 1: 321.594
run 2: 317.720

4 threads, journal disabled, journal compressor = zlib

run 1: 320.312
run 2: 318.326

Comment by Adam Comerford [ 11/Feb/15 ]

EDIT: removing previous udpate because I suspect something was stealing CPU cycles randomly on my client machine and creating variance. I cleaned things up and got the following results:

8 threads, journal: disabled, journalCompressor: none

run 1: 259.824s
run 2: 259.023s
run 3: 257.046s
run 4: 258.878s
avg: 258.693s (316668.792 inserts/sec)

8 threads, journal: disabled, journalCompressor: snappy

run 1: 258.777s
run 2: 258.329s
run 3: 258.320s
run 4: 257.852s
avg: 258.32s (317126.659 inserts/sec)

So, basically the same, at least for these tests where my client is the limiting factor (CPU bound). My server is not even breathing hard (<50% CPU, <50% IO)

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