Re: block: DMA alignment of IO buffer allocated from slab

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To: Matthew Wilcox <willy@xxxxxxxxxxxxx>, Ming Lei <ming.lei@xxxxxxxxxx>
Subject: Re: block: DMA alignment of IO buffer allocated from slab
From: Bart Van Assche <bvanassche@xxxxxxx>
Date: Mon, 24 Sep 2018 21:10:43 -0700
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>, Christoph Hellwig <hch@xxxxxx>, Ming Lei <tom.leiming@xxxxxxxxx>, linux-block <linux-block@xxxxxxxxxxxxxxx>, linux-mm <linux-mm@xxxxxxxxx>, Linux FS Devel <linux-fsdevel@xxxxxxxxxxxxxxx>, "open list:XFS FILESYSTEM" <linux-xfs@xxxxxxxxxxxxxxx>, Dave Chinner <dchinner@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Jens Axboe <axboe@xxxxxxxxx>, Christoph Lameter <cl@xxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
In-reply-to: <20180925032826.GA4110@bombadil.infradead.org>
References: <38c03920-0fd0-0a39-2a6e-70cd8cb4ef34@virtuozzo.com> <20a20568-5089-541d-3cee-546e549a0bc8@acm.org> <12eee877-affa-c822-c9d5-fda3aa0a50da@virtuozzo.com> <1537801706.195115.7.camel@acm.org> <c844c598-be1d-bef4-fb99-09cf99571fd7@virtuozzo.com> <1537804720.195115.9.camel@acm.org> <10c706fd-2252-f11b-312e-ae0d97d9a538@virtuozzo.com> <1537805984.195115.14.camel@acm.org> <20180924185753.GA32269@bombadil.infradead.org> <20180925001615.GA14386@ming.t460p> <20180925032826.GA4110@bombadil.infradead.org>
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On 9/24/18 8:28 PM, Matthew Wilcox wrote:

[ ... ] Because if we have to
round all allocations below 64 bytes up to 64 bytes, [ ... ]

Have you noticed that in another e-mail in this thread it has beenexplained why it is not necessary on x86 to align buffers allocated bykmalloc() on a 64-byte boundary even if these buffers are used for DMA?


Bart.

Follow-Ups:
- Re: block: DMA alignment of IO buffer allocated from slab
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References:
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Andrey Ryabinin
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Bart Van Assche
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Andrey Ryabinin
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Bart Van Assche
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Andrey Ryabinin
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Bart Van Assche
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Andrey Ryabinin
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Bart Van Assche
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Matthew Wilcox
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Ming Lei
- Re: block: DMA alignment of IO buffer allocated from slab
  - From: Matthew Wilcox

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