[wplug] cpu load?

[Brandon Poyner]

On 8/16/07, Bryan J Smith <b.j.smith at ieee.org> wrote:

> Third, if your disk is pegged, that's a possible sign of thrashing.
> Fortunately, there is an utility to measure that, vmstat.
> Use vmstat to see how much paging is going on,
> which will directly affect you disk I/O and bus usage.
> It should not, however, hit your CPU utilization to bad,
> unless there is a lot of processes running and context switching
> is eating up a lot of time waiting on I/O resources.

Just jumping in here to say that some disks are better than others at
handling I/O requests.  Parallel ATA (EIDE) drives are particularly
bad at handling requests that require many seeks by the drive head.
SCSI and SATA II have tagged command queuing and native command
queuing, respectively, that permit the drive to make smarter decisions
about seeking.

Also, not really related to updatedb, but another performance hit is
caused by mounting a partition with atime, usually the default for
most filesystems.  With atime enabled, very time you read a file, it
must update (write to) the inode.  That can be a killer when doing
things like backups.

-- 
Brandon
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