[Bug 635181] Re: High load average on Lucid for nominal/idle system use

[Chris]

(sigh) another drive by  comment for karma points.

In the NFS situation I would expect NFS tasks to 'float high' in regular
TOP.  No such items are seen at the top of top.  The 'meta' information
in iotop does not seem to be totally broken.  The Total Disk Read and
Disk Write stats though may be not as accurate in their totals they
still reflect activity under normal operation.   The "zero" I speak of
above is that line showing zero to a few byes of activity with rsync
sending the LA1 to 6 or more.

The issue manifests itself in NFS copying via rsync,  dd from /dev/zero
to a usb device, and on SATA to SATA moves of large VDI files.    If a
simple dd=/dev/zero of=/path/to/usb/file bs=1024 count=1M sends the load
average sky high (on two different guests on two different parents  and
one parent is running 10.04) something is wrong on 10.04.  It did not
operate this way before.   I should not need to render my parent or
guests  useless moving 30 GB vdi images from one disk spindle to
another.  Nor should I need to "put up with" (as seen in the sar output
attached to the case) load averages for idle systems that, for no
apparent reason, migrate above 1.00 or more.  If you had  read my other
posts on 574910 you would have noted that regressing the kernel to a
9.10 version improves the issue, but does not totally resolve it.

There are more instance types.  See my posts in  574910.


NB:   As to the "broken" state of iotop,   Only CONFIG_TASK_DELAY_ACCT
seems to be disabled in Lucid.   CONFIG_TASK_DELAY_ACCT used for intra-
task prioritization[1] and seems only to disable the SwapIn and IO %.
So, unless I have missed other posts where it states that iotop is
totally broken, the package is still valid for meta information.   (BTW
if  CONFIG_TASK_DELAY_ACCT  is disabled due to "performance" issues, why
not disable SMP on all kernels too since that is a performance hit too
for all non SMP hosts).


1 https://lists.ubuntu.com/archives/kernel-team/2009-December/008029.html

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High load average on Lucid for nominal/idle system use
https://bugs.launchpad.net/bugs/635181
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