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Type:
Improvement
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Resolution: Incomplete
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Priority:
Major - P3
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None
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Affects Version/s: 5.0.13
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Component/s: None
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Environment:Server: Icelake server
OS: Ubuntu 20.04.2 LTS
Kernel: 5.4.0-65-generic
Compiler: gcc version 10.3.0 (Ubuntu 10.3.0-1ubuntu1~20.04)
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Service Arch
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100
During the testing of Mongodb with YCSB client (at the time of experiment the YCSB java code only works with v5.0 of the server), uttampc discovered a large number of migrations statistics as reported by "perf stat" command. See details below,
| Event | Baseline | Baseline |
|---|---|---|
| Threads | 40 | 80 |
| Throughput | 337,008 | 304,580 |
| sched:sched_process_free | 13 | 18 |
| sched:sched_process_exit | 13 | 16 |
| sched:sched_process_wait | 34 | 34 |
| sched:sched_process_fork | 11 | 15 |
| sched:sched_process_exec | 10 | 11 |
| sched:sched_process_hang | 0 | 0 |
| task:task_newtask | 11 | 15 |
| task:task_rename | 10 | 14 |
| L1-dcache-loads | 1,406,341,217,349 | 1,321,016,036,512 |
| L1-dcache_load_misses | 140,998,950,663 | 148,306,686,642 |
| cycles | 8,938,835,361,677 | 9,556,957,123,623 |
| cs | 199,014,407 | 179,466,722 |
| migrations | 411,085 | 37,726,014 |
| Elapsed time (sec) | 60 | 60 |
As you can see from the table above, the migrations stats is quite high. With addition of few lines of "thread affinity" code in the "runFunc" function which is a thread function per connection, I was able to see almost 70% reduction in this number with a small improvement (2% to 5%) in overall throughput.
New data snapshot,
| Event | Thread-affinity | Thread-affinity |
|---|---|---|
| Threads | 40 | 80 |
| Throughput | 342,339 | 325,860 |
| migrations | 38,418 | 9,116,093 |
| Elapsed time (sec) | 60 | 60 |
I started with upstream docker version of mongodb server which was based on v5.0.13 at the time hence this PR is based on v5.0 branch.
No. records: 40M
Type of Request: Read-Only queries.
YCSB Commands:
Loading of the database:
$ python2.7 ./bin/ycsb load mongodb -jvm-args="-Dlogback.configurationFile=../logback.xml" -s -P workloads/workloadc -threads 20 -p mongodb.url=mongodb://localhost/ycsb
Execution of queries (40 threads)
$ python2.7 ./bin/ycsb run mongodb -jvm-args="-Dlogback.configurationFile=../logback.xml" -s -P workloads/workloadc -threads 40 -p mongodb.url=mongodb://localhost/ycsb
Execution of queries (80 threads)
$ python2.7 ./bin/ycsb run mongodb -jvm-args="-Dlogback.configurationFile=../logback.xml" -s -P workloads/workloadc -threads 80 -p mongodb.url=mongodb://localhost/ycsb
Perf command
$ sudo perf stat -e "sched:sched_process*,task:*,L1-dcache-loads,L1-dcache-load-misses,cycles,cs,faults,migrations" -d -d -d -a – sleep 60
- is related to
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SERVER-74243 Evaluate the implications of pinning threads
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- Backlog
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