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From: Roman Gushchin <guro@fb.com>
To: Christopher Lameter <cl@linux.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>, <linux-mm@kvack.org>,
	<kernel-team@fb.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 04/19] mm: slub: implement SLUB version of obj_to_index()
Date: Fri, 24 Apr 2020 19:46:25 -0700	[thread overview]
Message-ID: <20200425024625.GA107755@carbon.lan> (raw)
In-Reply-To: <alpine.DEB.2.21.2004250208500.7624@www.lameter.com>

On Sat, Apr 25, 2020 at 02:10:24AM +0000, Christoph Lameter wrote:
> 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?
> 
>

Please, take a look at the whole series:
https://lore.kernel.org/linux-mm/20200422204708.2176080-1-guro@fb.com/T/#t

I'm sorry, I had to cc you directly for the whole thing. Your feedback
will be highly appreciated.

It's used to calculate the offset of the memcg pointer for every slab
object which is charged to a memory cgroup. So it must be quite hot.

Thanks!

Roman

  reply	other threads:[~2020-04-25  2:46 UTC|newest]

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-22 20:46 [PATCH v3 00/19] The new cgroup slab memory controller Roman Gushchin
2020-04-22 20:46 ` [PATCH v3 01/19] mm: memcg: factor out memcg- and lruvec-level changes out of __mod_lruvec_state() Roman Gushchin
2020-05-07 20:33   ` Johannes Weiner
2020-05-20 10:49   ` Vlastimil Babka
2020-04-22 20:46 ` [PATCH v3 02/19] mm: memcg: prepare for byte-sized vmstat items Roman Gushchin
2020-05-07 20:34   ` Johannes Weiner
2020-05-20 11:31   ` Vlastimil Babka
2020-05-20 11:36     ` Vlastimil Babka
2020-04-22 20:46 ` [PATCH v3 03/19] mm: memcg: convert vmstat slab counters to bytes Roman Gushchin
2020-05-07 20:41   ` Johannes Weiner
2020-05-20 12:25   ` Vlastimil Babka
2020-05-20 19:26     ` Roman Gushchin
2020-05-21  9:57       ` Vlastimil Babka
2020-05-21 21:14         ` Roman Gushchin
2020-04-22 20:46 ` [PATCH v3 04/19] mm: slub: implement SLUB version of obj_to_index() Roman Gushchin
2020-04-22 23:52   ` Christopher Lameter
2020-04-23  0:05     ` Roman Gushchin
2020-04-25  2:10       ` Christopher Lameter
2020-04-25  2:46         ` Roman Gushchin [this message]
2020-04-27 16:21           ` Christopher Lameter
2020-04-27 16:46             ` Roman Gushchin
2020-04-28 17:06               ` Roman Gushchin
2020-04-28 17:45               ` Johannes Weiner
2020-04-30 16:29               ` Christopher Lameter
2020-04-30 17:15                 ` Roman Gushchin
2020-05-02 23:54                   ` Christopher Lameter
2020-05-04 18:29                     ` Roman Gushchin
2020-05-08 21:35                       ` Christopher Lameter
2020-05-13  0:57                         ` Roman Gushchin
2020-05-15 21:45                           ` Christopher Lameter
2020-05-15 22:12                             ` Roman Gushchin
2020-05-20  9:51                           ` Vlastimil Babka
2020-05-20 20:57                             ` Roman Gushchin
2020-05-15 20:02                         ` Roman Gushchin
2020-04-23 21:01     ` Roman Gushchin
2020-04-25  2:10       ` Christopher Lameter
2020-05-20 13:51   ` Vlastimil Babka
2020-05-20 21:00     ` Roman Gushchin
2020-05-21 11:01       ` Vlastimil Babka
2020-05-21 21:06         ` Roman Gushchin
2020-04-22 20:46 ` [PATCH v3 05/19] mm: memcontrol: decouple reference counting from page accounting Roman Gushchin
2020-04-22 20:46 ` [PATCH v3 06/19] mm: memcg/slab: obj_cgroup API Roman Gushchin
2020-05-07 21:03   ` Johannes Weiner
2020-05-07 22:26     ` Roman Gushchin
2020-05-12 22:56       ` Johannes Weiner
2020-05-15 22:01         ` Roman Gushchin
2020-04-22 20:46 ` [PATCH v3 07/19] mm: memcg/slab: allocate obj_cgroups for non-root slab pages Roman Gushchin
2020-04-23 20:20   ` Roman Gushchin
2020-05-22 18:27   ` Vlastimil Babka
2020-05-23  1:32     ` Roman Gushchin
2020-05-26 17:50     ` Roman Gushchin
2020-05-25 14:46   ` Vlastimil Babka
2020-04-22 20:46 ` [PATCH v3 08/19] mm: memcg/slab: save obj_cgroup for non-root slab objects Roman Gushchin
2020-05-25 15:07   ` Vlastimil Babka
2020-05-26 17:53     ` Roman Gushchin
2020-05-27 11:03       ` Vlastimil Babka
2020-04-22 20:46 ` [PATCH v3 09/19] mm: memcg/slab: charge individual slab objects instead of pages Roman Gushchin
2020-05-25 16:10   ` Vlastimil Babka
2020-05-26 18:04     ` Roman Gushchin
2020-04-22 20:46 ` [PATCH v3 10/19] mm: memcg/slab: deprecate memory.kmem.slabinfo Roman Gushchin
2020-05-07 21:05   ` Johannes Weiner
2020-04-22 20:47 ` [PATCH v3 11/19] mm: memcg/slab: move memcg_kmem_bypass() to memcontrol.h Roman Gushchin
2020-05-25 17:03   ` Vlastimil Babka
2020-04-22 20:47 ` [PATCH v3 12/19] mm: memcg/slab: use a single set of kmem_caches for all accounted allocations Roman Gushchin
2020-05-26 10:12   ` Vlastimil Babka
2020-04-22 20:47 ` [PATCH v3 13/19] mm: memcg/slab: simplify memcg cache creation Roman Gushchin
2020-05-26 10:31   ` Vlastimil Babka
2020-04-22 20:47 ` [PATCH v3 14/19] mm: memcg/slab: deprecate memcg_kmem_get_cache() Roman Gushchin
2020-05-26 10:34   ` Vlastimil Babka
2020-04-22 20:47 ` [PATCH v3 15/19] mm: memcg/slab: deprecate slab_root_caches Roman Gushchin
2020-05-26 10:52   ` Vlastimil Babka
2020-05-26 18:50     ` Roman Gushchin
2020-04-22 20:47 ` [PATCH v3 16/19] mm: memcg/slab: remove redundant check in memcg_accumulate_slabinfo() Roman Gushchin
2020-05-26 11:31   ` Vlastimil Babka
2020-04-22 20:47 ` [PATCH v3 17/19] mm: memcg/slab: use a single set of kmem_caches for all allocations Roman Gushchin
2020-05-26 14:55   ` Vlastimil Babka
2020-05-27  8:35     ` Jesper Dangaard Brouer
2020-04-22 20:47 ` [PATCH v3 18/19] kselftests: cgroup: add kernel memory accounting tests Roman Gushchin
2020-05-26 15:24   ` Vlastimil Babka
2020-05-26 15:45     ` Roman Gushchin
2020-05-27 17:00       ` Vlastimil Babka
2020-05-27 20:45         ` Roman Gushchin
2020-04-22 20:47 ` [PATCH v3 19/19] tools/cgroup: add memcg_slabinfo.py tool Roman Gushchin
2020-05-05 15:59   ` Tejun Heo

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