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

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Message-ID: <20200423210147.GA83398@carbon.DHCP.thefacebook.com>
Date:   Thu, 23 Apr 2020 14:01:47 -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. Place it with "align", inuse etc?
> 
> Hmmm. the same applies to min_partial maybe?
> 
>

Something like this?

Thanks!

--

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index cdf4f299c982..6246a3c65cd5 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -84,10 +84,8 @@ struct kmem_cache {
        struct kmem_cache_cpu __percpu *cpu_slab;
        /* Used for retrieving partial slabs, etc. */
        slab_flags_t flags;
-       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;
        unsigned int offset;    /* Free pointer offset */
 #ifdef CONFIG_SLUB_CPU_PARTIAL
        /* Number of per cpu partial objects to keep around */
@@ -103,6 +101,8 @@ struct kmem_cache {
        void (*ctor)(void *);
        unsigned int inuse;             /* Offset to metadata */
        unsigned int align;             /* Alignment */
+       unsigned long min_partial;
+       struct reciprocal_value reciprocal_size;
        unsigned int red_left_pad;      /* Left redzone padding size */
        const char *name;       /* Name (only for display!) */
        struct list_head list;  /* List of slab caches */