linux-kernel - Re: [PATCH] zfcp: add some internal zfcp adapter statistics

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Message-Id: <1195989419.3427.11.camel@localhost.localdomain>
Date:	Sun, 25 Nov 2007 13:16:59 +0200
From:	James Bottomley <James.Bottomley@...elEye.com>
To:	Swen Schillig <swen@...t.ibm.com>
Cc:	Christof Schmitt <christof.schmitt@...ibm.com>,
	linux-scsi@...r.kernel.org,
	Linux on 390 Port <LINUX-390@...marist.edu>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] zfcp: add some internal zfcp adapter statistics


On Wed, 2007-10-31 at 11:33 +0100, Swen Schillig wrote:
> From: Swen Schillig <swen@...t.ibm.com>
> 
> add some statistics provided by the zFCP adapter to the sysfs
> 
> The new zFCP adapter statistics provide a variety of information
> about the virtual adapter (subchannel). In order to collect this information
> the zFCP driver is extended on one side to query the adapter and
> on the other side summarize certain values which can then be fetched on demand.
> This information is made available via files(attributes) in the sysfs filesystem.
> 
> The information provided by the new zFCP adapter statistics can be fetched
> by reading from the following files in the sysfs filesystem
> 
>  /sys/class/scsi_host/host<n>/seconds_active
>  /sys/class/scsi_host/host<n>/requests
>  /sys/class/scsi_host/host<n>/megabytes
>  /sys/class/scsi_host/host<n>/utilization

This lot all look like they belong in the FC transport class statistics
(some even already exist there).

> These are the statistics on a virtual adapter (subchannel) level.
> In addition latency information is provided on a SCSI device level (LUN) which
> can be found at the following location
> 
>  /sys/class/scsi_device/<H:C:T:L>/device/cmd_latency
>  /sys/class/scsi_device/<H:C:T:L>/device/read_latency
>  /sys/class/scsi_device/<H:C:T:L>/device/write_latency

These look to duplicate to some degree the figures
in /sys/block/<dev>/stat.  Isn't the block device the best place to
gather these, if they're useful?  Since user latencies should probably
include elevator times.

James


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