https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=216759
Bug ID: 216759
Summary: [qemu] Memory speed significantly slower under QEMUKVM
emulation according to sysbench
Product: Base System
Version: 11.0-RELEASE
Hardware: Any
OS: Any
Status: New
Severity: Affects Some People
Priority: ---
Component: kern
Assignee: freebsd-bugs@FreeBSD.org
Reporter: and...@azar-a.net
FreeBSD 11-RELEASE and 10.3-RELEASE seem to run memory much slower according to
sysbench benchmarking software:
Bare Metal run:
# uname -a
FreeBSD backup 10.3-RELEASE-p11 FreeBSD 10.3-RELEASE-p11 #0: Mon Oct 24
18:49:24 UTC 2016
r...@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64
# sysbench --num-threads=1 --test=memory --memory-total-size=1G run
sysbench 0.4.12: multi-threaded system evaluation benchmark
Running the test with following options:
Number of threads: 1
Doing memory operations speed test
Memory block size: 1K
Memory transfer size: 1024M
Memory operations type: write
Memory scope type: global
Threads started!
Done.
Operations performed: 1048576 (2183178.34 ops/sec)
1024.00 MB transferred (2132.01 MB/sec)
Test execution summary:
total time: 0.4803s
total number of events: 1048576
total time taken by event execution: 0.3527
per-request statistics:
min: 0.00ms
avg: 0.00ms
max: 7.56ms
approx. 95 percentile: 0.00ms
Threads fairness:
events (avg/stddev): 1048576.0000/0.00
execution time (avg/stddev): 0.3527/0.00
QEMU KVM emulation:
# uname -a
FreeBSD dev 11.0-RELEASE-p2 FreeBSD 11.0-RELEASE-p2 #0: Mon Oct 24 06:55:27 UTC
2016 r...@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64
# sysbench --num-threads=1 --test=memory --memory-total-size=1G run
sysbench 0.4.12: multi-threaded system evaluation benchmark
Running the test with following options:
Number of threads: 1
Doing memory operations speed test
Memory block size: 1K
Memory transfer size: 1024M
Memory operations type: write
Memory scope type: global
Threads started!
Done.
Operations performed: 1048576 (69497.13 ops/sec)
1024.00 MB transferred (67.87 MB/sec)
Test execution summary:
total time: 15.0880s
total number of events: 1048576
total time taken by event execution: 11.1440
per-request statistics:
min: 0.01ms
avg: 0.01ms
max: 7.32ms
approx. 95 percentile: 0.00ms
Threads fairness:
events (avg/stddev): 1048576.0000/0.00
execution time (avg/stddev): 11.1440/0.00
For comparison
VMWARE:
# uname -a
FreeBSD ns3 10.2-RELEASE-p7 FreeBSD 10.2-RELEASE-p7 #0: Mon Nov 2 14:19:39 UTC
2015 r...@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64
# sysbench --num-threads=1 --test=memory --memory-total-size=1G run
sysbench 0.4.12: multi-threaded system evaluation benchmark
Running the test with following options:
Number of threads: 1
Doing memory operations speed test
Memory block size: 1K
Memory transfer size: 1024M
Memory operations type: write
Memory scope type: global
Threads started!
Done.
Operations performed: 1048576 (2234641.77 ops/sec)
1024.00 MB transferred (2182.27 MB/sec)
Test execution summary:
total time: 0.4692s
total number of events: 1048576
total time taken by event execution: 0.3437
per-request statistics:
min: 0.00ms
avg: 0.00ms
max: 0.09ms
approx. 95 percentile: 0.00ms
Threads fairness:
events (avg/stddev): 1048576.0000/0.00
execution time (avg/stddev): 0.3437/0.00
This is not 11 only problem. VPSs with 10.3 tested also have the same problem.
I haven't found any info on this on the net. Might be because nobody tests the
RAM.
Sysbench itself starts up a thread and runs the allocation code. I couldn't
trace the thread though.
Maybe it is old code of sysbench.
Additional information and reports:
https://www.reddit.com/r/freebsd/comments/5rtf05/abysmal_memory_perfomance_witch_freebsd_under/
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