RE: help converting zcache from sysfs to debugfs?

[Dan Magenheimer <dan.magenheimer@oracle.com>]

> From: Konrad Rzeszutek Wilk [mailto:konrad@darnok.org]
> Subject: Re: help converting zcache from sysfs to debugfs?
> 
> On Jun 19, 2012 8:30 PM, "Dan Magenheimer" <dan.magenheimer@oracle.com> wrote:
> >
> > Zcache (in staging) has a large number of read-only counters that
> > are primarily of interest to developers.  These counters are currently
> > visible from sysfs.  However sysfs is not really appropriate and
> > zcache will need to switch to debugfs before it can be promoted
> > out of staging.
> >
> > For some of the counters, it is critical that they remain accurate so
> > an atomic_t must be used.  But AFAICT there is no way for debugfs
> > to work with atomic_t.
> 
> Which ones must be atomic? Do they really need to be atomic if they are for diagnostics/developers?
>  :
> A dozen that _MUST_ be atomic?

Hi Konrad --

On second look, there are only eight.  They are unsigned, go
up and down, and the code needs to know if/when they are zero
(or BUG if they go below zero).  When viewed by a developer
(or very savvy administrator), they can be viewed directly or
feed into analysis tools that would likely get very confused
by "huge" ("negative unsigned") values.  Recently, Seth changed
one zcache counter from unsigned to atomic_t for this reason.

Thanks,
Dan

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