On Tue, 2009-10-20 at 20:54 +0200, Christof Schmitt wrote:
> On Fri, Oct 16, 2009 at 04:08:24PM -0700, Vasu Dev wrote:
> > -v3
> > Moves max_queue_depth initialization after slave_configure is
> > called from after slave_alloc calling done. Also adjusted
> > max_queue_depth check to skip ramp up if current queue_depth
> > is >= max_queue_depth.
> >
> > Signed-off-by: Vasu Dev <[email protected]>
>
> Looks good to me. I ran some tests on s390 and the queue depth counter
> increased until hitting the defined maximum.
>
Good.
> > @@ -779,6 +781,36 @@ static struct device_attribute
> > sdev_attr_queue_depth_rw =
> > sdev_store_queue_depth_rw);
> >
> > static ssize_t
> > +sdev_show_queue_ramp_up_period(struct device *dev,
> > + struct device_attribute *attr,
> > + char *buf)
> > +{
> > + struct scsi_device *sdev;
> > + sdev = to_scsi_device(dev);
> > + return snprintf(buf, 20, "%lu\n", sdev->queue_ramp_up_period);
> > +}
> > +
> > +static ssize_t
> > +sdev_store_queue_ramp_up_period(struct device *dev,
> > + struct device_attribute *attr,
> > + const char *buf, size_t count)
> > +{
> > + struct scsi_device *sdev = to_scsi_device(dev);
> > + unsigned long period;
> > +
> > + if (strict_strtoul(buf, 10, &period))
> > + return -EINVAL;
> > +
> > + sdev->queue_ramp_up_period = period;
> > + return period;
> > +}
>
> [...]
> > + unsigned long queue_ramp_up_period; /* ramp up period in jiffies */
> > +#define SCSI_DEFAULT_RAMP_UP_PERIOD (120 * HZ)
>
> Only a small inconvenience i guess: The sysfs attribute shows the
> ramp-up-period in jiffies. On my system with HZ==100 the default is
> 12000 and i was wondering if this would be milliseconds or something
> related. If HZ changes, the unit of the ramp-up-period also changes.
>
> I would prefer having seconds or milliseconds in sysfs and only using
> jiffies internally.
>
Added timestamp comparison checks are straightforward without any
additional conversion on each check since added timestamps and
queue_ramp_up_period both are jiffies, so works better this way with
stored queue_ramp_up_period in jiffies.
I do see your point as well but jiffies unit is also common in Linux.
However if you or some other feels strongly to change this to ms or
seconds unit then I could change store or show sysfs functions to handle
this value in ms or second unit while storing it in jiffies in
queue_ramp_up_period.
Vasu
> Thanks for doing this,
>
> Christof
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