linux-kernel - Re: [PATCH] mm/slub: improve count_partial() for CONFIG_SLUB_CPU

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Message-ID: <alpine.DEB.2.21.2002261827440.8012@www.lameter.com>
Date:   Wed, 26 Feb 2020 18:31:28 +0000 (UTC)
From:   Christopher Lameter <cl@...ux.com>
To:     Roman Gushchin <guro@...com>
cc:     Wen Yang <wenyang@...ux.alibaba.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Xunlei Pang <xlpang@...ux.alibaba.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/slub: improve count_partial() for
 CONFIG_SLUB_CPU_PARTIAL

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.