From: Christoph Hellwig <hch@lst.de>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>, Ming Lei <ming.lei@redhat.com>,
Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Dave Chinner <dchinner@redhat.com>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
"Darrick J . Wong" <darrick.wong@oracle.com>,
xfs@vger.kernel.org, Bart Van Assche <bvanassche@acm.org>
Subject: Re: [PATCH 0/5] block: introduce helpers for allocating io buffer from slab
Date: Thu, 18 Oct 2018 17:21:33 +0200 [thread overview]
Message-ID: <20181018152133.GA28300@lst.de> (raw)
In-Reply-To: <20181018150605.GC32429@bombadil.infradead.org>
On Thu, Oct 18, 2018 at 08:06:05AM -0700, Matthew Wilcox wrote:
> Can you name one that does require 512-byte alignment, preferably still
> in use? Or even >4-byte alignment. I just checked AHCI and that requires
> only 2-byte alignment.
Xen-blkfront, rsxx, various SD/MMC card readers for example.
> I have reason to believe that these are uncommon because of the feedback
> we got in the NVMe committee after releasing 1.0 which required 4-byte
> alignment from people whining that they just couldn't guarantee 4-byte
> alignment in their host devices and they absolutely needed to have no
> alignment requirements (!)
See how things turned - after NVMe SGLs followed the no alignment
rule enough controller vendors rebelled so that NVMe 1.3 has an option
of SGL support only if 4-byte aligned.
next prev parent reply other threads:[~2018-10-18 23:23 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-18 13:18 [PATCH 0/5] block: introduce helpers for allocating io buffer from slab Ming Lei
2018-10-18 13:18 ` [PATCH 1/5] block: warn on un-aligned DMA IO buffer Ming Lei
2018-10-18 14:27 ` Jens Axboe
2018-10-18 14:43 ` Christoph Hellwig
2018-10-18 14:46 ` Jens Axboe
2018-10-19 1:28 ` Ming Lei
2018-10-19 1:33 ` Jens Axboe
2018-10-19 1:39 ` Ming Lei
2018-10-19 1:52 ` Jens Axboe
2018-10-19 2:06 ` Ming Lei
2018-10-19 2:10 ` Jens Axboe
2018-10-18 14:28 ` Christoph Hellwig
2018-10-18 13:18 ` [PATCH 2/5] block: move .dma_alignment into q->limits Ming Lei
2018-10-18 14:29 ` Christoph Hellwig
2018-10-18 20:36 ` Bart Van Assche
2018-10-18 13:18 ` [PATCH 3/5] block: make dma_alignment as stacked limit Ming Lei
2018-10-18 14:31 ` Christoph Hellwig
2018-10-18 13:18 ` [PATCH 4/5] block: introduce helpers for allocating IO buffers from slab Ming Lei
2018-10-18 14:42 ` Christoph Hellwig
2018-10-18 15:11 ` Matthew Wilcox
2018-10-18 15:22 ` Christoph Hellwig
2018-10-19 2:53 ` Ming Lei
2018-10-19 4:06 ` Jens Axboe
2018-10-19 5:43 ` Dave Chinner
2018-10-18 13:18 ` [PATCH 5/5] xfs: use block layer helpers to allocate io buffer " Ming Lei
2018-10-18 14:03 ` [PATCH 0/5] block: introduce helpers for allocating " Matthew Wilcox
2018-10-18 14:05 ` Christoph Hellwig
2018-10-18 15:06 ` Matthew Wilcox
2018-10-18 15:21 ` Christoph Hellwig [this message]
2018-10-18 15:50 ` Bart Van Assche
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