Re: [PATCH] mm/slub: improve count_partial() for CONFIG_SLUB_CPU_PARTIAL

From: Christopher Lameter <cl@linux.com>
To: Roman Gushchin <guro@fb.com>
Cc: Wen Yang <wenyang@linux.alibaba.com>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Xunlei Pang <xlpang@linux.alibaba.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/slub: improve count_partial() for CONFIG_SLUB_CPU_PARTIAL
Date: Wed, 26 Feb 2020 18:31:28 +0000 (UTC)	[thread overview]
Message-ID: <alpine.DEB.2.21.2002261827440.8012@www.lameter.com> (raw)
In-Reply-To: <20200224165750.GA478187@carbon.dhcp.thefacebook.com>

On Mon, 24 Feb 2020, Roman Gushchin wrote:

> > I suggest that you simply use the number of partial slabs and multiply
> > them by the number of objects in a slab and use that as a value. Both
> > values are readily available via /sys/kernel/slab/<...>/
>
> So maybe something like this?
>
> @@ -5907,7 +5907,9 @@ void get_slabinfo(struct kmem_cache *s, struct slabinfo *sinfo)
>  	for_each_kmem_cache_node(s, node, n) {
>  		nr_slabs += node_nr_slabs(n);
>  		nr_objs += node_nr_objs(n);
> +#ifndef CONFIG_SLUB_CPU_PARTIAL
>  		nr_free += count_partial(n, count_free);
> +#endif
>  	}

Why would not having cpu partials screws up the counting of objects in
partial slabs?

You dont need kernel mods for this. The numbers are exposed already in
/sys/kernel/slab/xxx.