Re: [PATCH V3] block/throttle: Add IO throttled information inblkio.throttle

From: Vivek Goyal
Date: Fri Oct 19 2012 - 15:39:34 EST

On Fri, Oct 19, 2012 at 12:36:00PM -0700, Tejun Heo wrote:
> Hello, Vivek.
> On Fri, Oct 19, 2012 at 11:00:11AM -0400, Vivek Goyal wrote:
> > > That way we can stick to the usual stats facility.
> >
> > So how does this help? Because it is a monotonically increasing value
> > we can use per cpu stats without extra locking? Or somthing else?
> It's generally much simpler to expose dumb increasing counters. You
> don't have to worry about mismatching decrements (for whatever reason,
> percpu or segmented counters), so unless there's a pretty good reason
> to deviate, why deviate?

I really can't think of a reason to deviate. I was just curious of
advantages. I think it does make sense to not get into decrement business
and let user space subtract two values and figure out how much IO from
the group is throttled.

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