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SubjectRe: Eradic disk access during reads
Date
Denis Vlasenko wrote:
> > > > Monitoring disk access using gkrellm, I noticed that a command like
> > > >
> > > > cat /dev/hda > /dev/null
> > > >
> > > > shows eradic disk reads ranging from 0 to 80MB/s on an otherwise
> > > > idle system.
> > > >
> > > > 1. Is this a hardware or software problem?
> > >
> > > Difficult to tell without more info. Can be a broken IDE disk or
> > > defective ribbon.
> >
> > Tried the same with 2.4.31 which shows steady behaviour with occasional
> > dips and pops in the msec range.
> >
> > > > 2. Is there a lightweight perf-mon tool (cmd-line) that would log
> > > > this behaviour graphically?
>
> Try attached one.

Nice!

> # dd if=/dev/hda of=/dev/null bs=16M

This is what I got; what do you get?

Thanks!

2.4.31 # nmeter t6 c x i b d100
18:56:36.009981 cpu [SSSSSSSS..] ctx 145 int 86 bio 4.7M 0
18:56:36.110327 cpu [SSSSSSSS..] ctx 145 int 87 bio 4.8M 0
18:56:36.210735 cpu [SSSSSSSS..] ctx 139 int 88 bio 4.7M 0
18:56:36.310315 cpu [SSSSSSSS..] ctx 142 int 85 bio 4.7M 0
18:56:36.409979 cpu [SSSSSS....] ctx 147 int 86 bio 4.7M 0
18:56:36.510764 cpu [SSSSSSSSS.] ctx 161 int 88 bio 4.8M 0
18:56:36.610213 cpu [SSSSSSSS..] ctx 165 int 85 bio 4.7M 0
18:56:36.710194 cpu [SSSSSSSSS.] ctx 152 int 89 bio 4.7M 4096
18:56:36.809977 cpu [SSSSSSS...] ctx 135 int 86 bio 4.7M 0
18:56:36.909970 cpu [SSSSSSS...] ctx 142 int 89 bio 4.7M 16k
18:56:37.009972 cpu [SSSSS.....] ctx 130 int 86 bio 4.7M 0
18:56:37.109979 cpu [SSSSS.....] ctx 142 int 86 bio 4.7M 0
18:56:37.210335 cpu [SSSSSSSS..] ctx 135 int 87 bio 4.8M 0
18:56:37.309973 cpu [SSSSS.....] ctx 100 int 68 bio 3.5M 0
18:56:37.410011 cpu [SSSSSSS...] ctx 146 int 87 bio 4.7M 0
18:56:37.509980 cpu [SSSSSSS...] ctx 145 int 86 bio 4.8M 0
18:56:37.610117 cpu [SSSSSSS...] ctx 137 int 87 bio 4.7M 0
18:56:37.709978 cpu [SSSSSSSSS.] ctx 133 int 87 bio 4.7M 0
18:56:37.809981 cpu [SSSSSSSS..] ctx 146 int 87 bio 4.8M 0
18:56:37.909972 cpu [SSSSS.....] ctx 139 int 86 bio 4.7M 0
18:56:38.010504 cpu [SSSSSS....] ctx 149 int 87 bio 4.7M 0
18:56:38.110025 cpu [SSSSSSS...] ctx 136 int 87 bio 4.7M 0
18:56:38.210122 cpu [SSSSSSS...] ctx 137 int 85 bio 4.7M 0
18:56:38.309975 cpu [SSSSSSS...] ctx 141 int 87 bio 4.7M 0
18:56:38.410095 cpu [SSSSSSSS..] ctx 138 int 86 bio 4.8M 0
18:56:38.509978 cpu [SSSSS.....] ctx 145 int 87 bio 4.7M 0
18:56:38.610115 cpu [SSSSS.....] ctx 145 int 86 bio 4.7M 0
18:56:38.710204 cpu [SSSSSSSS..] ctx 141 int 87 bio 4.7M 0
18:56:38.811411 cpu [SSSSSSS...] ctx 128 int 88 bio 4.8M 0
18:56:38.911221 cpu [SSSSSSSS..] ctx 131 int 86 bio 4.7M 0
18:56:39.010779 cpu [SSSSSSSS..] ctx 127 int 86 bio 4.7M 0
18:56:39.110211 cpu [SSSSS.....] ctx 127 int 86 bio 4.7M 0
18:56:39.210086 cpu [SSSSSSSSS.] ctx 131 int 86 bio 4.7M 0
18:56:39.313572 cpu [SSSSSSS...] ctx 137 int 90 bio 5.0M 0
18:56:39.410307 cpu [SSSSSSS...] ctx 139 int 84 bio 4.6M 0
18:56:39.510618 cpu [SSSSSSSSS.] ctx 131 int 85 bio 4.7M 0
18:56:39.610558 cpu [SSSSSSSS..] ctx 144 int 87 bio 4.7M 0
18:56:39.709981 cpu [SSSS......] ctx 141 int 86 bio 4.7M 0
18:56:39.810109 cpu [SSSSSSS...] ctx 139 int 86 bio 4.7M 0
18:56:39.910581 cpu [SSSSSSS...] ctx 144 int 87 bio 4.8M 0
18:56:40.010554 cpu [SSSSSSSSS.] ctx 144 int 87 bio 4.7M 0
18:56:40.110382 cpu [SSSSSSSS..] ctx 143 int 86 bio 4.7M 0
18:56:40.210709 cpu [SSSSSSSSS.] ctx 138 int 87 bio 4.8M 0
18:56:40.310512 cpu [SSSS......] ctx 144 int 86 bio 4.7M 0
18:56:40.410830 cpu [SSSSSSS...] ctx 147 int 87 bio 4.7M 0
18:56:40.510371 cpu [SSSSSSSS..] ctx 160 int 86 bio 4.7M 0
18:56:40.610664 cpu [SSSSSSSS..] ctx 170 int 87 bio 4.8M 0
18:56:40.710106 cpu [SSSSSSS...] ctx 149 int 87 bio 4.7M 0
18:56:40.810056 cpu [SSSSSSSS..] ctx 141 int 85 bio 4.6M 0
18:56:40.910416 cpu [SSSSSSS...] ctx 138 int 86 bio 4.8M 0
18:56:41.009974 cpu [SSSSSS....] ctx 142 int 87 bio 4.7M 0
18:56:41.110094 cpu [SSSSSS....] ctx 142 int 86 bio 4.7M 0
18:56:41.209972 cpu [SSSSSSSS..] ctx 139 int 87 bio 4.7M 0
18:56:41.310140 cpu [SSSSSSSS..] ctx 135 int 88 bio 4.8M 0

2.6.13 # nmeter t6 c x i b d100
18:09:22.117959 cpu [SSSSSSSSSD] ctx 80 int 47 bio 4.7M 0
18:09:22.217932 cpu [SSSSSSDDDD] ctx 83 int 48 bio 4.8M 0
18:09:22.319200 cpu [SSSSDDDDDI] ctx 81 int 56 bio 4.7M 28k
18:09:22.407979 cpu [SSSSSSSSSD] ctx 60 int 38 bio 3.8M 0
18:09:22.517960 cpu [SSSSSSSSDI] ctx 95 int 61 bio 5.2M 52k
18:09:22.617942 cpu [SSSSSSSSSD] ctx 77 int 47 bio 4.7M 0
18:09:22.718043 cpu [SSSSSDDDDD] ctx 81 int 48 bio 4.8M 0
18:09:22.817976 cpu [SSSSDDDDDD] ctx 80 int 48 bio 4.6M 0
18:09:22.918080 cpu [SSSSSSSDDI] ctx 80 int 48 bio 4.8M 0
18:09:23.017975 cpu [SSSSSSSSDD] ctx 80 int 47 bio 4.7M 0
18:09:23.117912 cpu [SSSSDDDDDD] ctx 36 int 25 bio 3.1M 0
18:09:23.217943 cpu [SSSSDDDDDD] ctx 44 int 29 bio 2.7M 0
18:09:23.317949 cpu [SSSSSSSDDD] ctx 80 int 47 bio 4.8M 0
18:09:23.417944 cpu [SSSSSSSSDI] ctx 84 int 49 bio 4.7M 0
18:09:23.517944 cpu [SSSSSSSSDD] ctx 78 int 47 bio 4.7M 0
18:09:23.617948 cpu [SSSSDDDDDD] ctx 67 int 42 bio 4.5M 8192
18:09:23.718238 cpu [SSSSDDDDDD] ctx 80 int 48 bio 4.7M 0
18:09:23.818039 cpu [SSSSSSSDDI] ctx 79 int 48 bio 4.7M 0
18:09:23.917961 cpu [SSSSSSSSDD] ctx 80 int 49 bio 4.7M 0
18:09:24.019101 cpu [SSSSSSSDDD] ctx 80 int 48 bio 4.8M 0
18:09:24.107934 cpu [SSSSSSSDII] ctx 71 int 42 bio 4.2M 0
18:09:24.217946 cpu [SSSSDDDDDD] ctx 90 int 53 bio 5.2M 0
18:09:24.317965 cpu [SSSSSSDDDI] ctx 83 int 49 bio 4.7M 0
18:09:24.417974 cpu [SSSSSSSSDD] ctx 78 int 46 bio 4.6M 0
18:09:24.517938 cpu [SSSSDDDDDD] ctx 48 int 30 bio 3.7M 0
18:09:24.617940 cpu [SSSDDDDDDD] ctx 80 int 48 bio 4.7M 0
18:09:24.717948 cpu [SSSSSSSDDI] ctx 79 int 48 bio 4.7M 0
18:09:24.817955 cpu [SSSSSSSSDI] ctx 82 int 49 bio 4.7M 0
18:09:24.917914 cpu [SSSSDDDDDD] ctx 31 int 21 bio 2.7M 0
18:09:25.018051 cpu [SSSDDDDDDD] ctx 31 int 23 bio 2.7M 0
18:09:25.117988 cpu [SSSSSSDDII] ctx 81 int 49 bio 4.8M 0
18:09:25.217970 cpu [SSSSSDDDDD] ctx 37 int 24 bio 3.1M 0
18:09:25.318115 cpu [SSSSSSSSDD] ctx 81 int 48 bio 4.8M 0
18:09:25.417959 cpu [SSSSSSSSDD] ctx 81 int 47 bio 4.7M 0
18:09:25.517943 cpu [SSSSSSDDDD] ctx 65 int 41 bio 4.3M 0
18:09:25.617959 cpu [SSSSDDDDDD] ctx 80 int 48 bio 4.7M 0
18:09:25.717945 cpu [SSSSSSSDDD] ctx 81 int 47 bio 4.8M 0
18:09:25.817979 cpu [SSSSSSSSDI] ctx 79 int 49 bio 4.6M 0
18:09:25.917913 cpu [SSSSDDDDDD] ctx 30 int 21 bio 2.7M 0
18:09:26.017940 cpu [SSSSDDDDDD] ctx 64 int 39 bio 3.7M 0
18:09:26.118932 cpu [SSSSDDDDDI] ctx 79 int 49 bio 4.7M 0
18:09:26.217959 cpu [SSSSSDDDDD] ctx 43 int 26 bio 3.3M 0
18:09:26.317948 cpu [SSSSSDDDDD] ctx 64 int 38 bio 4.1M 0
18:09:26.417962 cpu [SSSSSSSSDD] ctx 78 int 47 bio 4.7M 0
18:09:26.517958 cpu [SSSSDDDDDD] ctx 27 int 20 bio 2.2M 0
18:09:26.617978 cpu [SSSDDDDDDD] ctx 24 int 18 bio 1.6M 0
18:09:26.717966 cpu [SSSSSDDDDI] ctx 76 int 45 bio 4.5M 0
18:09:26.817963 cpu [SSSSSSDDDI] ctx 62 int 37 bio 4.0M 0
18:09:26.917972 cpu [SSSSSDDDDD] ctx 69 int 40 bio 4.3M 0
18:09:27.017971 cpu [SSSSSSSDDD] ctx 78 int 47 bio 4.7M 0
18:09:27.117942 cpu [SDDDDDDDDD] ctx 40 int 25 bio 3.3M 0
18:09:27.217949 cpu [SSSSSSSSDI] ctx 69 int 42 bio 4.2M 0
18:09:27.318990 cpu [SSSSSSSSDI] ctx 84 int 48 bio 4.8M 0
18:09:27.417950 cpu [SSSSSSSSSI] ctx 79 int 47 bio 4.6M 0
18:09:27.518161 cpu [SSSSSSSSDI] ctx 79 int 47 bio 4.8M 8192
18:09:27.617941 cpu [SSSSSSSDDD] ctx 87 int 51 bio 4.7M 24k

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