From: Vlastimil Babka <vbabka@suse.cz>
To: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Jesper Dangaard Brouer <brouer@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 16/16] mm/slab: introduce new slab management type, OBJFREELIST_SLAB
Date: Fri, 29 Jan 2016 16:21:30 +0100 [thread overview]
Message-ID: <56AB837A.5090702@suse.cz> (raw)
In-Reply-To: <20160128045128.GC14467@js1304-P5Q-DELUXE>
On 01/28/2016 05:51 AM, Joonsoo Kim wrote:
> On Wed, Jan 27, 2016 at 02:35:04PM +0100, Vlastimil Babka wrote:
>> On 01/14/2016 06:24 AM, Joonsoo Kim wrote:
>> > In fact, I tested another idea implementing OBJFREELIST_SLAB with
>> > extendable linked array through another freed object. It can remove
>> > memory waste completely but it causes more computational overhead
>> > in critical lock path and it seems that overhead outweigh benefit.
>> > So, this patch doesn't include it.
>>
>> Can you elaborate? Do we actually need an extendable linked array? Why not just
>> store the pointer to the next free object into the object, NULL for the last
>> one? I.e. a singly-linked list. We should never need to actually traverse it?
>
> As Christoph explained, it's the way SLUB manages freed objects. In SLAB
> case, it doesn't want to touch object itself. It's one of main difference
> between SLAB and SLUB. These objects are cache-cold now so touching object itself
> could cause more cache footprint.
Hm I see. Although I wouldn't bet on whether the now-freed object is more or
less cold than the freelist array itself (regardless of its placement) :)
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WARNING: multiple messages have this Message-ID (diff)
From: Vlastimil Babka <vbabka@suse.cz>
To: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Jesper Dangaard Brouer <brouer@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 16/16] mm/slab: introduce new slab management type, OBJFREELIST_SLAB
Date: Fri, 29 Jan 2016 16:21:30 +0100 [thread overview]
Message-ID: <56AB837A.5090702@suse.cz> (raw)
In-Reply-To: <20160128045128.GC14467@js1304-P5Q-DELUXE>
On 01/28/2016 05:51 AM, Joonsoo Kim wrote:
> On Wed, Jan 27, 2016 at 02:35:04PM +0100, Vlastimil Babka wrote:
>> On 01/14/2016 06:24 AM, Joonsoo Kim wrote:
>> > In fact, I tested another idea implementing OBJFREELIST_SLAB with
>> > extendable linked array through another freed object. It can remove
>> > memory waste completely but it causes more computational overhead
>> > in critical lock path and it seems that overhead outweigh benefit.
>> > So, this patch doesn't include it.
>>
>> Can you elaborate? Do we actually need an extendable linked array? Why not just
>> store the pointer to the next free object into the object, NULL for the last
>> one? I.e. a singly-linked list. We should never need to actually traverse it?
>
> As Christoph explained, it's the way SLUB manages freed objects. In SLAB
> case, it doesn't want to touch object itself. It's one of main difference
> between SLAB and SLUB. These objects are cache-cold now so touching object itself
> could cause more cache footprint.
Hm I see. Although I wouldn't bet on whether the now-freed object is more or
less cold than the freelist array itself (regardless of its placement) :)
next prev parent reply other threads:[~2016-01-29 15:21 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-14 5:24 [PATCH 00/16] mm/slab: introduce new freed objects management way, OBJFREELIST_SLAB Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 01/16] mm/slab: fix stale code comment Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 15:22 ` Christoph Lameter
2016-01-14 15:22 ` Christoph Lameter
2016-01-14 5:24 ` [PATCH 02/16] mm/slab: remove useless structure define Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 15:22 ` Christoph Lameter
2016-01-14 15:22 ` Christoph Lameter
2016-01-14 5:24 ` [PATCH 03/16] mm/slab: remove the checks for slab implementation bug Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 15:23 ` Christoph Lameter
2016-01-14 15:23 ` Christoph Lameter
2016-01-14 16:20 ` Joonsoo Kim
2016-01-14 16:20 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 04/16] mm/slab: activate debug_pagealloc in SLAB when it is actually enabled Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 12:09 ` Jesper Dangaard Brouer
2016-01-14 12:09 ` Jesper Dangaard Brouer
2016-01-14 16:16 ` Joonsoo Kim
2016-01-14 16:16 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 05/16] mm/slab: use more appropriate condition check for debug_pagealloc Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 06/16] mm/slab: clean-up DEBUG_PAGEALLOC processing code Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 07/16] mm/slab: alternative implementation for DEBUG_SLAB_LEAK Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 08/16] mm/slab: remove object status buffer " Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 09/16] mm/slab: put the freelist at the end of slab page Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 15:26 ` Christoph Lameter
2016-01-14 15:26 ` Christoph Lameter
2016-01-14 16:21 ` Joonsoo Kim
2016-01-14 16:21 ` Joonsoo Kim
2016-01-14 17:13 ` Christoph Lameter
2016-01-14 17:13 ` Christoph Lameter
2016-01-14 5:24 ` [PATCH 10/16] mm/slab: align cache size first before determination of OFF_SLAB candidate Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 11/16] mm/slab: clean-up cache type determination Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 12/16] mm/slab: do not change cache size if debug pagealloc isn't possible Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 13/16] mm/slab: make criteria for off slab determination robust and simple Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 14/16] mm/slab: factor out slab list fixup code Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 15/16] mm/slab: factor out debugging initialization in cache_init_objs() Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 5:24 ` [PATCH 16/16] mm/slab: introduce new slab management type, OBJFREELIST_SLAB Joonsoo Kim
2016-01-14 5:24 ` Joonsoo Kim
2016-01-14 15:32 ` Christoph Lameter
2016-01-14 15:32 ` Christoph Lameter
2016-01-14 16:24 ` Joonsoo Kim
2016-01-14 16:24 ` Joonsoo Kim
2016-01-27 13:35 ` Vlastimil Babka
2016-01-27 13:35 ` Vlastimil Babka
2016-01-27 16:48 ` Christoph Lameter
2016-01-27 16:48 ` Christoph Lameter
2016-01-27 17:18 ` Vlastimil Babka
2016-01-27 17:18 ` Vlastimil Babka
2016-01-27 17:55 ` Christoph Lameter
2016-01-27 17:55 ` Christoph Lameter
2016-01-28 4:51 ` Joonsoo Kim
2016-01-28 4:51 ` Joonsoo Kim
2016-01-29 15:21 ` Vlastimil Babka [this message]
2016-01-29 15:21 ` Vlastimil Babka
2016-01-27 4:40 ` [PATCH 00/16] mm/slab: introduce new freed objects management way, OBJFREELIST_SLAB Andrew Morton
2016-01-27 4:40 ` Andrew Morton
2016-01-27 4:46 ` Joonsoo Kim
2016-01-27 4:46 ` Joonsoo Kim
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