From: Vlastimil Babka <vbabka@suse.cz>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christopher Lameter <cl@linux.com>,
linux-mm@kvack.org, Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Ming Lei <ming.lei@redhat.com>,
Dave Chinner <david@fromorbit.com>,
"Darrick J . Wong" <darrick.wong@oracle.com>,
Christoph Hellwig <hch@lst.de>, Michal Hocko <mhocko@kernel.org>,
linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org
Subject: Re: [RFC 0/2] guarantee natural alignment for kmalloc()
Date: Thu, 21 Mar 2019 08:02:32 +0100 [thread overview]
Message-ID: <718a767c-5f0c-7435-3f9b-c63bcd5b488f@suse.cz> (raw)
In-Reply-To: <20190321022355.GA19508@bombadil.infradead.org>
On 3/21/19 3:23 AM, Matthew Wilcox wrote:
> On Wed, Mar 20, 2019 at 10:48:03PM +0100, Vlastimil Babka wrote:
>>
>> Well, looks like that's what happens. This is with SLAB, but the alignment
>> calculations should be common:
>>
>> slabinfo - version: 2.1
>> # name <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> : tunables <limit> <batchcount> <sharedfactor> : slabdata <active_slabs> <num_slabs> <sharedavail>
>> kmalloc-96 2611 4896 128 32 1 : tunables 120 60 8 : slabdata 153 153 0
>> kmalloc-128 4798 5536 128 32 1 : tunables 120 60 8 : slabdata 173 173 0
>
> Hmm. On my laptop, I see:
>
> kmalloc-96 28050 35364 96 42 1 : tunables 0 0 0 : slabdata 842 842 0
>
> That'd take me from 842 * 4k pages to 1105 4k pages -- an extra megabyte of
> memory.
>
> This is running Debian's 4.19 kernel:
>
> # CONFIG_SLAB is not set
> CONFIG_SLUB=y
Ah, you're right. SLAB creates kmalloc caches with:
#ifndef ARCH_KMALLOC_FLAGS
#define ARCH_KMALLOC_FLAGS SLAB_HWCACHE_ALIGN
#endif
create_kmalloc_caches(ARCH_KMALLOC_FLAGS);
While SLUB just:
create_kmalloc_caches(0);
even though it uses SLAB_HWCACHE_ALIGN for kmem_cache_node and
kmem_cache caches.
prev parent reply other threads:[~2019-03-21 7:02 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-19 21:11 [RFC 0/2] guarantee natural alignment for kmalloc() Vlastimil Babka
2019-03-19 21:11 ` [RFC 1/2] mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two) Vlastimil Babka
2019-03-19 21:11 ` [RFC 2/2] mm, sl[aou]b: test whether kmalloc() alignment works as expected Vlastimil Babka
2019-03-20 0:44 ` Christopher Lameter
2019-03-20 0:43 ` [RFC 0/2] guarantee natural alignment for kmalloc() Christopher Lameter
2019-03-20 0:53 ` David Rientjes
2019-03-20 8:48 ` Vlastimil Babka
2019-03-20 18:20 ` Christopher Lameter
2019-03-21 7:42 ` Vlastimil Babka
2019-03-22 17:52 ` Christopher Lameter
2019-04-05 17:11 ` Vlastimil Babka
2019-04-07 8:00 ` Christoph Hellwig
2019-04-09 8:07 ` Vlastimil Babka
2019-04-09 9:20 ` Michal Hocko
2019-03-20 18:53 ` Matthew Wilcox
2019-03-20 21:48 ` Vlastimil Babka
2019-03-21 2:23 ` Matthew Wilcox
2019-03-21 7:02 ` Vlastimil Babka [this message]
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