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

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Date:   Wed, 22 Apr 2020 17:05:30 -0700
From:   Roman Gushchin <guro@...com>
To:     Christopher Lameter <cl@...ux.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, 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.

> Place it with "align", inuse etc?
> 
> Hmmm. the same applies to min_partial maybe?
> 
> 

And min_partial should much colder.

So maybe a patch on top of the series which moves both fields can work?

Thanks!