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: Wed, 20 Mar 2019 22:48:03 +0100 [thread overview]
Message-ID: <b5290e04-6f29-c237-78a7-511821183efe@suse.cz> (raw)
In-Reply-To: <20190320185347.GZ19508@bombadil.infradead.org>
On 3/20/2019 7:53 PM, Matthew Wilcox wrote:
> On Wed, Mar 20, 2019 at 09:48:47AM +0100, Vlastimil Babka wrote:
>> Natural alignment to size is rather well defined, no? Would anyone ever
>> assume a larger one, for what reason?
>> It's now where some make assumptions (even unknowingly) for natural
>> There are two 'odd' sizes 96 and 192, which will keep cacheline size
>> alignment, would anyone really expect more than 64 bytes?
>
> Presumably 96 will keep being aligned to 32 bytes, as aligning 96 to 64
> just results in 128-byte allocations.
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
next prev parent reply other threads:[~2019-03-20 21:48 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 [this message]
2019-03-21 2:23 ` Matthew Wilcox
2019-03-21 7:02 ` Vlastimil Babka
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