From: Christopher Lameter <cl@linux.com>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
Ming Lei <ming.lei@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Christoph Hellwig <hch@lst.de>, Ming Lei <tom.leiming@gmail.com>,
linux-block <linux-block@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
"open list:XFS FILESYSTEM" <linux-xfs@vger.kernel.org>,
Dave Chinner <dchinner@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Jens Axboe <axboe@kernel.dk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: block: DMA alignment of IO buffer allocated from slab
Date: Mon, 24 Sep 2018 15:17:16 +0000 [thread overview]
Message-ID: <010001660c27f079-7ba54431-6f0c-430a-8db5-2398a8e761f0-000000@email.amazonses.com> (raw)
In-Reply-To: <20a20568-5089-541d-3cee-546e549a0bc8@acm.org>
On Mon, 24 Sep 2018, Bart Van Assche wrote:
> /*
> * kmalloc and friends return ARCH_KMALLOC_MINALIGN aligned
> * pointers. kmem_cache_alloc and friends return ARCH_SLAB_MINALIGN
> * aligned pointers.
> */
kmalloc alignment is only guaranteed to ARCH_KMALLOC_MINALIGN. That power
of 2 byte caches (without certain options) are aligned to the power of 2
is due to the nature that these objects are stored in SLUB. Other
allocators may behave different and actually different debug options
result in different alignments. You cannot rely on that.
ARCH_KMALLOC minalign shows the mininum alignment guarantees. If that is
not sufficient and you do not want to change the arch guarantees then you
can open you own slab cache with kmem_cache_create() where you can specify
different alignment requirements.
next prev parent reply other threads:[~2018-09-24 15:17 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-19 9:15 block: DMA alignment of IO buffer allocated from slab Ming Lei
2018-09-19 9:41 ` Vitaly Kuznetsov
2018-09-19 10:02 ` Ming Lei
2018-09-19 11:15 ` Vitaly Kuznetsov
2018-09-20 1:28 ` Ming Lei
2018-09-20 3:59 ` Yang Shi
2018-09-20 6:32 ` Christoph Hellwig
2018-09-20 6:31 ` Christoph Hellwig
2018-09-21 13:04 ` Vitaly Kuznetsov
2018-09-21 13:05 ` Christoph Hellwig
2018-09-21 15:00 ` Jens Axboe
2018-09-24 16:06 ` Christopher Lameter
2018-09-24 17:49 ` Jens Axboe
2018-09-24 18:00 ` Christopher Lameter
2018-09-24 18:09 ` Jens Axboe
2018-09-25 7:49 ` Dave Chinner
2018-09-25 15:44 ` Jens Axboe
2018-09-25 21:04 ` Matthew Wilcox
2018-09-23 22:42 ` Ming Lei
2018-09-24 9:46 ` Andrey Ryabinin
2018-09-24 14:19 ` Bart Van Assche
2018-09-24 14:43 ` Andrey Ryabinin
2018-09-24 15:08 ` Bart Van Assche
2018-09-24 15:52 ` Andrey Ryabinin
2018-09-24 15:58 ` Bart Van Assche
2018-09-24 16:07 ` Andrey Ryabinin
2018-09-24 16:19 ` Bart Van Assche
2018-09-24 16:47 ` Christopher Lameter
2018-09-24 18:57 ` Matthew Wilcox
2018-09-24 19:56 ` Bart Van Assche
2018-09-24 20:41 ` Matthew Wilcox
2018-09-24 20:54 ` Bart Van Assche
2018-09-24 21:09 ` Matthew Wilcox
2018-09-25 0:16 ` Ming Lei
2018-09-25 3:28 ` Matthew Wilcox
2018-09-25 4:10 ` Bart Van Assche
2018-09-25 4:44 ` Matthew Wilcox
2018-09-25 6:55 ` Ming Lei
2018-09-24 15:17 ` Christopher Lameter [this message]
2018-09-25 0:20 ` Ming Lei
2018-09-20 14:07 ` Bart Van Assche
2018-09-21 1:56 ` Dave Chinner
2018-09-21 7:08 ` Christoph Hellwig
2018-09-21 7:25 ` Ming Lei
2018-09-21 14:59 ` Jens Axboe
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