Re: Eradic disk access during reads

[Denis Vlasenko]

> > > > # dd if=/dev/hda of=/dev/null bs=16M
> > > 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
> > >
> > > 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
> >
> > Well, I do not see any bursts you mention...
> 
> Can you try 2.4.31?

Not easy. I guess I have quite a few 2.6-only things here...

> same here.
> 
> > My CPU is not that new:
> 
> PII - 400Mhz here.

I meant that kernel seem to eat too much CPU here. This
is not expected. I expected CPU bar to be all D.
 
> > hdc (an old disk):
> > 13:52:40.201718 cpu [SSSDDDDDDD] ctx   26 int  112 bio 1.2M    0
> > 13:52:40.301569 cpu [SSDDDDDDDD] ctx   28 int  109 bio 1.2M    0
> > 13:52:40.402552 cpu [SSDDDDDDDI] ctx   23 int  111 bio 1.2M    0
> > 13:52:40.502535 cpu [SSDDDDDDDD] ctx   22 int  110 bio 1.2M    0
> > 13:52:40.601507 cpu [SSDDDDDDDI] ctx   26 int  111 bio 1.2M    0
> > 13:52:40.701493 cpu [SSDDDDDDDD] ctx   23 int  110 bio 1.2M    0
> 
> Looks smooth.
> 
> Also, great meter!  Best of all does not hog the CPU!
> Could you add a top3 procs display?

What is a "top3 procs display"?
--
vda
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