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Date:   Tue, 8 Aug 2023 11:59:09 +0200
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Subject: Re: [RFC 2/2] mm/slub: prefer NUMA locality over slight memory saving
 on NUMA machines
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To:     Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc:     Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        David Rientjes <rientjes@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Feng Tang <feng.tang@intel.com>,
        "Sang, Oliver" <oliver.sang@intel.com>,
        Jay Patel <jaypatel@linux.ibm.com>,
        Binder Makin <merimus@google.com>, aneesh.kumar@linux.ibm.com,
        tsahu@linux.ibm.com, piyushs@linux.ibm.com, fengwei.yin@intel.com,
        ying.huang@intel.com, lkp <lkp@intel.com>,
        "oe-lkp@lists.linux.dev" <oe-lkp@lists.linux.dev>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
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From:   Vlastimil Babka <vbabka@suse.cz>
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On 8/7/23 10:39, Hyeonggon Yoo wrote:
> On Thu, Aug 3, 2023 at 11:54 PM Vlastimil Babka <vbabka@suse.cz> wrote:
>>
> 
> Thank you for looking at it!
> 
> Yeah, it was a PoC for what I thought "oh, it might be useful"
> and definitely I will try to measure it.
> 
>> We could also postpone this until we have tried the percpu arrays
>> improvements discussed at LSF/MM.
> 
> Possibly, but can you please share your plans/opinions on it?

Here's the very first attempt :)
https://lore.kernel.org/linux-mm/20230808095342.12637-7-vbabka@suse.cz/

> I think one possible way is simply to allow the cpu freelist to be
> mixed by objects from different slabs

I didn't try that way, might be much trickier than it looks.

> if we want to minimize changes, Or introduce a per cpu array similar
> to what SLAB does now.

Yes.

> And one thing I'm having difficulty understanding is - what is the
> mind behind/or impact of managing objects
> on a slab basis, other than avoiding array queues in 2007?

"The mind" is Christoph's so I'll leave that question to him :)