[Bug 216759] [kern] Memory speed with small blocks (1K) up to 35 times slower than host system under QEMU emulation

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=216759

Bartek Rutkowski <robak at freebsd.org> changed:

           What    |Removed                     |Added
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                 CC|                            |robak at freebsd.org

--- Comment #5 from Bartek Rutkowski <robak at freebsd.org> ---
Here are some results from the tests on a 12-C vm under XenServer:

VM: FreeBSD poudriere 12.0-CURRENT FreeBSD 12.0-CURRENT #3 r314028: Tue Feb 21
08:07:02 CET 2017    
root at pd.valinor.palantiri.org:/usr/obj/usr/src/sys/POUDRIERE  amd64

XenServer: Linux xenserver 3.10.0+10 #1 SMP Thu Sep 22 12:31:44 UTC 2016 x86_64
x86_64 x86_64 GNU/Linux, Xen version: 4.6.1-xs133690

DD on 8G mdisk:

# dd if=/dev/zero of=/dev/md1 bs=1M
dd: /dev/md1: end of device
8193+0 records in
8192+0 records out
8589934592 bytes transferred in 15.565112 secs (551871047 bytes/sec)

# dd if=/dev/zero of=/dev/md1 bs=1K
dd: /dev/md1: end of device
8388609+0 records in
8388608+0 records out
8589934592 bytes transferred in 232.354641 secs (36969068 bytes/sec)

Sysbench:

# sysbench --num-threads=1 --test=memory --memory-total-size=8G 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: 8192M

Memory operations type: write
Memory scope type: global
Threads started!
Done.

Operations performed: 8388608 (1169942.57 ops/sec)

8192.00 MB transferred (1142.52 MB/sec)


Test execution summary:
    total time:                          7.1701s
    total number of events:              8388608
    total time taken by event execution: 5.2679
    per-request statistics:
         min:                                  0.00ms
         avg:                                  0.00ms
         max:                                  3.95ms
         approx.  95 percentile:               0.00ms

Threads fairness:
    events (avg/stddev):           8388608.0000/0.00
    execution time (avg/stddev):   5.2679/0.00



# sysbench --num-threads=1 --test=memory --memory-total-size=8G
--memory-block-size=1M 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: 1024K

Memory transfer size: 8192M

Memory operations type: write
Memory scope type: global
Threads started!
Done.

Operations performed: 8192 (46849.56 ops/sec)

8192.00 MB transferred (46849.56 MB/sec)


Test execution summary:
    total time:                          0.1749s
    total number of events:              8192
    total time taken by event execution: 0.1727
    per-request statistics:
         min:                                  0.02ms
         avg:                                  0.02ms
         max:                                  0.08ms
         approx.  95 percentile:               0.03ms

Threads fairness:
    events (avg/stddev):           8192.0000/0.00
    execution time (avg/stddev):   0.1727/0.00

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