linux-kernel - Re: [PATCH 2/7] mm: shrinker: Add a .to

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Date:   Tue, 28 Nov 2023 12:48:53 -0500
From:   Kent Overstreet <kent.overstreet@...ux.dev>
To:     Michal Hocko <mhocko@...e.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>
Subject: Re: [PATCH 2/7] mm: shrinker: Add a .to_text() method for shrinkers

On Tue, Nov 28, 2023 at 11:01:16AM +0100, Michal Hocko wrote:
> On Wed 22-11-23 18:25:07, Kent Overstreet wrote:
> [...]
> > +void shrinkers_to_text(struct seq_buf *out)
> > +{
> > +	struct shrinker *shrinker;
> > +	struct shrinker_by_mem {
> > +		struct shrinker	*shrinker;
> > +		unsigned long	mem;
> > +	} shrinkers_by_mem[10];
> > +	int i, nr = 0;
> > +
> > +	if (!mutex_trylock(&shrinker_mutex)) {
> > +		seq_buf_puts(out, "(couldn't take shrinker lock)");
> > +		return;
> > +	}
> > +
> > +	list_for_each_entry(shrinker, &shrinker_list, list) {
> > +		struct shrink_control sc = { .gfp_mask = GFP_KERNEL, };
> 
> This seems to be global reclaim specific. What about memcg reclaim?

I have no fsckin idea how memcg reclaim works - and, for that matter,
the recent lockless shrinking work seems to have neglected to write even
an iterator macro, leaving _that_ a nasty mess so I'm not touching that
either.