linux-kernel - Re: [PATCH v3 04/19] mm: slub: implement SLUB version of obj_to

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Date:   Sat, 25 Apr 2020 02:10:24 +0000 (UTC)
From:   Christopher Lameter <cl@...ux.com>
To:     Roman Gushchin <guro@...com>
cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>, linux-mm@...ck.org,
        kernel-team@...com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 04/19] mm: slub: implement SLUB version of
 obj_to_index()

On Wed, 22 Apr 2020, Roman Gushchin wrote:

> On Wed, Apr 22, 2020 at 11:52:13PM +0000, Christoph Lameter wrote:
> > On Wed, 22 Apr 2020, Roman Gushchin wrote:
> >
> > >  enum stat_item {
> > >  	ALLOC_FASTPATH,		/* Allocation from cpu slab */
> > > @@ -86,6 +87,7 @@ struct kmem_cache {
> > >  	unsigned long min_partial;
> > >  	unsigned int size;	/* The size of an object including metadata */
> > >  	unsigned int object_size;/* The size of an object without metadata */
> > > +	struct reciprocal_value reciprocal_size;
> >
> >
> > This needs to be moved further back since it is not an item that needs to
> > be cache hot for the hotpaths.
>
> It could be relatively hot, because it's accessed for reading on every
> accounted allocation.

The patch seems to only use it for setup and debugging? It is used for
every "accounted" allocation???? Where? And what is an "accounted"
allocation?