xen-devel
[Xen-devel] question about disk performance in domU
Hi all,
When I ran the experiments to compare an application's execution time in both a domU (named cctest1)
and a native Linux machine (named ccn10), I noticed the application executes faster in domU. The
host of the domU (named ccn9) and ccn10 are two nodes of a cluster and they have same hardware
configurations. domU (cctest1) is created by exporting loopback files from dom0 on ccn9 as VBD
backends. The application execution logs there might be some disk I/O difference between cctest and
ccn10, so I did some disk performance profiling with "hdparms" on cctest1 (domU), ccn10 (native
Linux), ccn9 (dom0), and ccn9 (native Linux). Also, I checked the "DMA" config information from the
output of dmesg. I tried to run "hdparm -i" and "hdparm -I" but they didn't work. Seems they didn't
work with SCSI disks. The following are the results.
Thanks in advance for your help.
Best,
Xuehai
1. cctest1 (dumU)
**************************************************************************************************
cctest1$ df -lh
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 1.5G 1.1G 306M 78% /
tmpfs 62M 4.0K 62M 1% /dev/shm
/dev/sda6 4.2G 3.6G 453M 89% /tmp
/dev/sda5 938M 205M 685M 23% /var
cctest1$ dmesg | grep DMA
DMA zone: 101376 pages, LIFO batch:16
cctest1$ for i in `seq 1 10`; do hdparm -tT /dev/sda1; done
Timing cached reads: 512 MB in 2.00 seconds = 256.00 MB/sec
Timing buffered disk reads: 44 MB in 3.00 seconds = 14.67 MB/sec
Timing cached reads: 528 MB in 2.01 seconds = 262.69 MB/sec
Timing buffered disk reads: 84 MB in 3.08 seconds = 27.27 MB/sec
Timing cached reads: 520 MB in 2.00 seconds = 260.00 MB/sec
Timing buffered disk reads: 120 MB in 3.06 seconds = 39.22 MB/sec
Timing cached reads: 520 MB in 2.00 seconds = 260.00 MB/sec
Timing buffered disk reads: 150 MB in 3.06 seconds = 49.02 MB/sec
Timing cached reads: 536 MB in 2.00 seconds = 268.00 MB/sec
Timing buffered disk reads: 178 MB in 3.17 seconds = 56.15 MB/sec
Timing cached reads: 536 MB in 2.00 seconds = 268.00 MB/sec
Timing buffered disk reads: 204 MB in 3.08 seconds = 66.23 MB/sec
Timing cached reads: 532 MB in 2.00 seconds = 266.00 MB/sec
Timing buffered disk reads: 228 MB in 3.13 seconds = 72.84 MB/sec
Timing cached reads: 540 MB in 2.01 seconds = 268.66 MB/sec
Timing buffered disk reads: 248 MB in 3.04 seconds = 81.58 MB/sec
Timing cached reads: 540 MB in 2.00 seconds = 270.00 MB/sec
Timing buffered disk reads: 266 MB in 3.06 seconds = 86.93 MB/sec
Timing cached reads: 532 MB in 2.00 seconds = 266.00 MB/sec
Timing buffered disk reads: 282 MB in 3.06 seconds = 92.16 MB/sec
**************************************************************************************************
2. ccn10 (native Linux)
**************************************************************************************************
ccn10$ df -lh
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 1.5G 1.3G 149M 90% /
tmpfs 252M 0 252M 0% /dev/shm
/dev/sda6 4.2G 3.6G 358M 92% /tmp
/dev/sda5 938M 706M 184M 80% /var
ccn10$ dmesg | grep DMA
DMA zone: 4096 pages, LIFO batch:1
ccn10$ for i in `seq 1 10`; do hdparm -tT /dev/sda1; done
Timing cached reads: 516 MB in 2.00 seconds = 257.78 MB/sec
Timing buffered disk reads: 62 MB in 3.03 seconds = 20.47 MB/sec
Timing cached reads: 524 MB in 2.01 seconds = 261.00 MB/sec
Timing buffered disk reads: 62 MB in 3.01 seconds = 20.61 MB/sec
Timing cached reads: 516 MB in 2.00 seconds = 257.65 MB/sec
Timing buffered disk reads: 62 MB in 3.01 seconds = 20.61 MB/sec
Timing cached reads: 524 MB in 2.00 seconds = 262.04 MB/sec
Timing buffered disk reads: 62 MB in 3.01 seconds = 20.61 MB/sec
Timing cached reads: 516 MB in 2.00 seconds = 257.78 MB/sec
Timing buffered disk reads: 62 MB in 3.02 seconds = 20.51 MB/sec
Timing cached reads: 524 MB in 2.00 seconds = 261.78 MB/sec
Timing buffered disk reads: 62 MB in 3.02 seconds = 20.52 MB/sec
Timing cached reads: 516 MB in 2.00 seconds = 257.78 MB/sec
Timing buffered disk reads: 62 MB in 3.02 seconds = 20.51 MB/sec
Timing cached reads: 524 MB in 2.00 seconds = 261.78 MB/sec
Timing buffered disk reads: 62 MB in 3.02 seconds = 20.50 MB/sec
Timing cached reads: 516 MB in 2.00 seconds = 257.40 MB/sec
Timing buffered disk reads: 64 MB in 3.09 seconds = 20.73 MB/sec
Timing cached reads: 524 MB in 2.01 seconds = 260.87 MB/sec
Timing buffered disk reads: 62 MB in 3.01 seconds = 20.61 MB/sec
**************************************************************************************************
3. ccn9 (dom0)
**************************************************************************************************
ccn9$ df -lh
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 1.5G 1.1G 306M 78% /
tmpfs 62M 4.0K 62M 1% /dev/shm
/dev/sda6 4.2G 3.6G 453M 89% /tmp
/dev/sda5 938M 205M 685M 23% /var
ccn9$ dmesg | grep DMA
DMA zone: 32768 pages, LIFO batch:8
ccn9$ for i in `seq 1 10`; do hdparm -tT /dev/sda1; done
Timing cached reads: 504 MB in 2.00 seconds = 252.00 MB/sec
Timing buffered disk reads: 60 MB in 3.14 seconds = 19.11 MB/sec
Timing cached reads: 516 MB in 2.00 seconds = 258.00 MB/sec
Timing buffered disk reads: 62 MB in 3.15 seconds = 19.68 MB/sec
Timing cached reads: 512 MB in 2.00 seconds = 256.00 MB/sec
Timing buffered disk reads: 60 MB in 3.08 seconds = 19.48 MB/sec
Timing cached reads: 516 MB in 2.00 seconds = 258.00 MB/sec
Timing buffered disk reads: 58 MB in 3.02 seconds = 19.21 MB/sec
Timing cached reads: 516 MB in 2.01 seconds = 256.72 MB/sec
Timing buffered disk reads: 60 MB in 3.12 seconds = 19.23 MB/sec
Timing cached reads: 520 MB in 2.00 seconds = 260.00 MB/sec
Timing buffered disk reads: 60 MB in 3.13 seconds = 19.17 MB/sec
Timing cached reads: 520 MB in 2.01 seconds = 258.71 MB/sec
Timing buffered disk reads: 60 MB in 3.13 seconds = 19.17 MB/sec
Timing cached reads: 520 MB in 2.01 seconds = 258.71 MB/sec
Timing buffered disk reads: 60 MB in 3.06 seconds = 19.61 MB/sec
Timing cached reads: 516 MB in 2.01 seconds = 256.72 MB/sec
Timing buffered disk reads: 60 MB in 3.14 seconds = 19.11 MB/sec
Timing cached reads: 516 MB in 2.00 seconds = 258.00 MB/sec
Timing buffered disk reads: 60 MB in 3.15 seconds = 19.05 MB/sec
**************************************************************************************************
4. ccn9 (native Linux)
**************************************************************************************************
ccn9$ df -lh
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 1.5G 1.1G 306M 78% /
tmpfs 62M 4.0K 62M 1% /dev/shm
/dev/sda6 4.2G 3.6G 453M 89% /tmp
/dev/sda5 938M 205M 685M 23% /var
ccn9 $ dmesg | grep DMA
DMA zone: 4096 pages, LIFO batch:1
ccn9$ for i in `seq 1 10`; do hdparm -tT /dev/sda1; done
/dev/sda1:
Timing cached reads: 492 MB in 2.01 seconds = 244.57 MB/sec
Timing buffered disk reads: 62 MB in 3.10 seconds = 20.01 MB/sec
Timing cached reads: 484 MB in 2.01 seconds = 241.07 MB/sec
Timing buffered disk reads: 48 MB in 3.01 seconds = 15.95 MB/sec
Timing cached reads: 484 MB in 2.00 seconds = 241.67 MB/sec
Timing buffered disk reads: 62 MB in 3.03 seconds = 20.45 MB/sec
Timing cached reads: 484 MB in 2.01 seconds = 241.31 MB/sec
Timing buffered disk reads: 62 MB in 3.01 seconds = 20.57 MB/sec
Timing cached reads: 480 MB in 2.01 seconds = 239.08 MB/sec
Timing buffered disk reads: 62 MB in 3.03 seconds = 20.49 MB/sec
Timing cached reads: 488 MB in 2.01 seconds = 243.31 MB/sec
Timing buffered disk reads: 62 MB in 3.05 seconds = 20.31 MB/sec
Timing cached reads: 484 MB in 2.01 seconds = 241.31 MB/sec
Timing buffered disk reads: 62 MB in 3.01 seconds = 20.61 MB/sec
Timing cached reads: 484 MB in 2.00 seconds = 241.67 MB/sec
Timing buffered disk reads: 62 MB in 3.01 seconds = 20.59 MB/sec
Timing cached reads: 488 MB in 2.01 seconds = 242.34 MB/sec
Timing buffered disk reads: 62 MB in 3.01 seconds = 20.59 MB/sec
Timing cached reads: 484 MB in 2.01 seconds = 240.35 MB/sec
Timing buffered disk reads: 62 MB in 3.09 seconds = 20.09 MB/sec
**************************************************************************************************
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