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From: Mel Gorman <mgorman@suse.de>
To: Michal Hocko <mhocko@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Aruna Ramakrishna <aruna.ramakrishna@oracle.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jiri Slaby <jslaby@suse.cz>
Subject: Re: what is the purpose of SLAB and SLUB (was: Re: [PATCH v3] mm/slab: Improve performance of gathering slabinfo) stats
Date: Wed, 24 Aug 2016 09:20:57 +0100	[thread overview]
Message-ID: <20160824082057.GT2693@suse.de> (raw)
In-Reply-To: <20160823153807.GN23577@dhcp22.suse.cz>

On Tue, Aug 23, 2016 at 05:38:08PM +0200, Michal Hocko wrote:
> Do we have any documentation/study about which particular workloads
> benefit from which allocator? It seems that most users will use whatever
> the default or what their distribution uses. E.g. SLES kernel use SLAB
> because this is what we used to have for ages and there was no strong
> reason to change that default.

Yes, with the downside that a reliance on high-orders contended on the
zone lock which would not scale and could degrade over time. If there
were multiple compelling reasons then it would have been an easier
switch.

I did prototype high-order pcp caching up to PAGE_ALLOC_COSTLY_ORDER
but it pushed the size of per_cpu_pages over a cache line which could
be problematic in itself. I never finished off the work as fixing the
allocator for SLUB was not a priority. The prototype no longer applies as
it conflicts with the removal of the fair zone allocation policy.

If/when I get back to the page allocator, the priority would be a bulk
API for faster allocs of batches of order-0 pages instead of allocating
a large page and splitting.

-- 
Mel Gorman
SUSE Labs

  parent reply	other threads:[~2016-08-24  8:21 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-17 18:20 [PATCH v3] mm/slab: Improve performance of gathering slabinfo stats Aruna Ramakrishna
2016-08-17 19:03 ` Eric Dumazet
2016-08-17 19:25   ` Aruna Ramakrishna
2016-08-18 11:52 ` Michal Hocko
2016-08-19  5:47   ` aruna.ramakrishna
2016-08-23  2:13   ` Joonsoo Kim
2016-08-23 15:38     ` what is the purpose of SLAB and SLUB (was: Re: [PATCH v3] mm/slab: Improve performance of gathering slabinfo) stats Michal Hocko
2016-08-23 15:54       ` what is the purpose of SLAB and SLUB Andi Kleen
2016-08-25  4:10         ` Christoph Lameter
2016-08-25  7:32           ` Michal Hocko
2016-08-25 19:49             ` Christoph Lameter
2016-08-24  1:15       ` what is the purpose of SLAB and SLUB (was: Re: [PATCH v3] mm/slab: Improve performance of gathering slabinfo) stats Joonsoo Kim
2016-08-24  8:05         ` Michal Hocko
2016-08-24  8:20       ` Mel Gorman [this message]
2016-08-25  4:01         ` Christoph Lameter
2016-08-25 10:07           ` Mel Gorman
2016-08-25 19:55             ` Christoph Lameter
2016-08-26 20:47               ` what is the purpose of SLAB and SLUB Andi Kleen
2016-08-29 13:44                 ` Michal Hocko
2016-08-29 14:49                   ` Christoph Lameter
2016-08-30  9:39               ` what is the purpose of SLAB and SLUB (was: Re: [PATCH v3] mm/slab: Improve performance of gathering slabinfo) stats Mel Gorman
2016-08-30 19:32                 ` Christoph Lameter

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