Re: help converting zcache from sysfs to debugfs?

[Konrad Rzeszutek Wilk <konrad@darnok.org>]

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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?
>
> Is that correct?  Or am I missing something?
>
> Assuming it is correct, I have a workaround but it is ugly:
>
> static unsigned long counterX;
> static atomic_t atomic_counterX;
>
>        counterX = atomic_*_return(atomic_counterX)
>
> and use atomic_counter in normal code and counter for debugfs.
>
> This works but requires each counter to be stored twice AND
> makes the code look ugly.

But only for those counters that truly must be atomic.
>
> Is there a better way?  I can probably bury the ugliness in
> macros but that doesn't solve the duplicate storage.  (Though
> since there are only about a dozen, maybe it doesn't matter?)

A dozen that _MUST_ be atomic?

>
> Thanks,
> Dan
>
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