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pcp updates: raw disk time metrics for iostat emulation

To: pcp@xxxxxxxxxxx
Subject: pcp updates: raw disk time metrics for iostat emulation
From: Nathan Scott <nathans@xxxxxxxxxx>
Date: Thu, 27 Sep 2012 00:32:11 -0400 (EDT)
Reply-to: Nathan Scott <nathans@xxxxxxxxxx>
Changes committed to git://oss.sgi.com/pcp/pcp.git dev

 src/pmdas/linux/help              |   40 ++++++++++++++++++++++++++++++++++++++
 src/pmdas/linux/pmda.c            |   20 +++++++++++++++++++
 src/pmdas/linux/proc_partitions.c |   31 +++++++++++++++++++++--------
 src/pmdas/linux/root_linux        |    4 +++
 4 files changed, 87 insertions(+), 8 deletions(-)

commit 7afea63c7a1ff976b51ce688674acbc29ca2d703
Author: Nathan Scott <nathans@xxxxxxxxxx>
Date:   Thu Sep 27 14:26:58 2012 +1000

    Add "raw" disk active metrics so that existing tools can be emulated
    
    As requested by someone familiar with iostat.  If ever someone were
    to implement/augment iostat using PCP APIs, then these metrics will
    be needed.  They export /proc/diskstats read/write "ticks" fields.
    
    $ pminfo -T disk.dev.read_rawactive
    Help:
    When converted to a rate, this metric represents the raw utilization of
    the disk during the sampling interval as a result of reads.  Accounting for
    this metric is only done on I/O completion and can thus result in more than 
a
    second's worth of IO being accounted for within any one second, leading to
    >100% utilisation.  It is suitable mainly for use in calculations with other
    metrics, e.g. mirroring the results from existing performance tools:
    
     iostat.dev.r_await = delta(disk.dev.read_rawactive) / delta(disk.dev.read)

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