On Wed, 15 Jul 2009, Richard Elling wrote:
heh. What you would be looking for is evidence of prefetching. If
there is a lot of prefetching, the actv will tend to be high and
latencies relatively low. If there is no prefetching, actv will be
low and latencies may be higher. This also implies that if you use
IDE disks, which cannot handle multiple outstanding I/Os, the
performance will look similar for both runs.
Ok, here are some stats for the "poor" (initial "USB" rates) and
"terrible" (sub-"USB" rates) cases.
"poor" (29% busy) iostat:
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c0t0d0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c1t0d0
0.0 1.2 0.0 11.4 0.0 0.0 0.0 4.5 0 0 c1t1d0
91.2 0.0 11654.7 0.0 0.0 0.8 0.0 9.2 0 27
c4t600A0B80003A8A0B0000096147B451BEd0
95.0 0.0 12160.3 0.0 0.0 0.9 0.0 9.9 0 29
c4t600A0B800039C9B500000A9C47B4522Dd0
96.4 0.0 12333.1 0.0 0.0 0.9 0.0 9.5 0 29
c4t600A0B800039C9B500000AA047B4529Bd0
96.8 0.0 12377.9 0.0 0.0 0.9 0.0 9.5 0 30
c4t600A0B80003A8A0B0000096647B453CEd0
100.4 0.0 12845.1 0.0 0.0 1.0 0.0 9.5 0 29
c4t600A0B800039C9B500000AA447B4544Fd0
93.4 0.0 11949.1 0.0 0.0 0.8 0.0 9.0 0 28
c4t600A0B80003A8A0B0000096A47B4559Ed0
91.5 0.0 11705.9 0.0 0.0 0.9 0.0 9.7 0 28
c4t600A0B800039C9B500000AA847B45605d0
91.4 0.0 11680.3 0.0 0.0 0.9 0.0 10.1 0 29
c4t600A0B80003A8A0B0000096E47B456DAd0
88.9 0.0 11366.7 0.0 0.0 0.9 0.0 9.7 0 27
c4t600A0B800039C9B500000AAC47B45739d0
94.3 0.0 12045.5 0.0 0.0 0.9 0.0 9.9 0 29
c4t600A0B800039C9B500000AB047B457ADd0
96.5 0.0 12339.5 0.0 0.0 0.9 0.0 9.3 0 28
c4t600A0B80003A8A0B0000097347B457D4d0
87.9 0.0 11232.7 0.0 0.0 0.9 0.0 10.4 0 29
c4t600A0B800039C9B500000AB447B4595Fd0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c5t0d0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c6t0d0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0
c2t202400A0B83A8A0Bd31
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0
c3t202500A0B83A8A0Bd31
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 freddy:vold(pid508)
"terrible" (8% busy) iostat:
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c0t0d0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c1t0d0
0.0 1.8 0.0 1.0 0.0 0.0 0.0 26.6 0 1 c1t1d0
26.8 0.0 3430.4 0.0 0.0 0.1 0.0 2.9 0 8
c4t600A0B80003A8A0B0000096147B451BEd0
21.0 0.0 2688.0 0.0 0.0 0.1 0.0 3.9 0 8
c4t600A0B800039C9B500000A9C47B4522Dd0
24.0 0.0 3059.6 0.0 0.0 0.1 0.0 3.4 0 8
c4t600A0B800039C9B500000AA047B4529Bd0
27.6 0.0 3532.8 0.0 0.0 0.1 0.0 3.2 0 9
c4t600A0B80003A8A0B0000096647B453CEd0
20.8 0.0 2662.4 0.0 0.0 0.1 0.0 3.1 0 6
c4t600A0B800039C9B500000AA447B4544Fd0
26.5 0.0 3392.0 0.0 0.0 0.1 0.0 2.6 0 7
c4t600A0B80003A8A0B0000096A47B4559Ed0
20.6 0.0 2636.8 0.0 0.0 0.1 0.0 3.0 0 6
c4t600A0B800039C9B500000AA847B45605d0
22.9 0.0 2931.2 0.0 0.0 0.1 0.0 3.8 0 9
c4t600A0B80003A8A0B0000096E47B456DAd0
21.4 0.0 2739.2 0.0 0.0 0.1 0.0 3.5 0 7
c4t600A0B800039C9B500000AAC47B45739d0
23.1 0.0 2944.4 0.0 0.0 0.1 0.0 3.7 0 9
c4t600A0B800039C9B500000AB047B457ADd0
24.9 0.0 3187.2 0.0 0.0 0.1 0.0 3.4 0 8
c4t600A0B80003A8A0B0000097347B457D4d0
28.3 0.0 3622.4 0.0 0.0 0.1 0.0 2.8 0 8
c4t600A0B800039C9B500000AB447B4595Fd0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c5t0d0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c6t0d0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0
c2t202400A0B83A8A0Bd31
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0
c3t202500A0B83A8A0Bd31
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 freddy:vold(pid508)
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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