Re: [PATCH 2/7] mm: shrinker: Add a .to_text() method for shrinkers

[Qi Zheng]

Hi Kent,

On 2023/11/24 05:24, Kent Overstreet wrote:
> On Thu, Nov 23, 2023 at 11:32:59AM +0800, Qi Zheng wrote:
> > > +	void (*to_text)(struct seq_buf *, struct shrinker *);
> >
> > The "to_text" looks a little strange, how about naming it
> > "stat_objects"?
>
> The convention I've been using heavily in bcachefs is
> typename_to_text(), or type.to_text(), for debug reports. The

OK.

> consistency is nice.

However, this is inconsistent with the name style of other
shrinker callbacks. Please use the "objects" suffix. As for
bcachefs's own callback function, you can use typename_to_text()
to ensure consistency.

Thanks,
Qi

> > >    	long batch;	/* reclaim batch size, 0 = default */
> > >    	int seeks;	/* seeks to recreate an obj */
> > > @@ -110,7 +114,6 @@ struct shrinker {
> > >    #endif
> > >    #ifdef CONFIG_SHRINKER_DEBUG
> > >    	int debugfs_id;
> > > -	const char *name;
> >
> > The name will only be allocated memory when the CONFIG_SHRINKER_DEBUG is
> > enabled, otherwise its value is NULL. So you can't move it out and use
> > it while CONFIG_SHRINKER_DEBUG is disabled.
>
> Good catch
>
> > > +void shrinkers_to_text(struct seq_buf *out)
> > > +{
> > > +	struct shrinker *shrinker;
> > > +	struct shrinker_by_mem {
> > > +		struct shrinker	*shrinker;
> > > +		unsigned long	mem;
> >
> > The "mem" also looks a little strange, how about naming it
> > "freeable"?
>
> The type is just used in this one function, but sure.
>
> > > +	} shrinkers_by_mem[10];
> > > +	int i, nr = 0;
> > > +
> > > +	if (!mutex_trylock(&shrinker_mutex)) {
> > > +		seq_buf_puts(out, "(couldn't take shrinker lock)");
> > > +		return;
> > > +	}
> >
> > We now have lockless method (RCU + refcount) to iterate shrinker_list,
> > please refer to shrink_slab().
>
> Will do!