From: willy@linux.intel.com (Matthew Wilcox)
Subject: SGL support of driver
Date: Thu, 30 Jul 2015 14:38:28 -0400 [thread overview]
Message-ID: <20150730183828.GY13681@linux.intel.com> (raw)
In-Reply-To: <20150729075557.GA11755@infradead.org>
On Wed, Jul 29, 2015@12:55:57AM -0700, Christoph Hellwig wrote:
> 64k page size, 4k file system block size, raid 0 with a stripe size of
> 8k and two legs.
>
> The typical SGL feds to the hardware driver for streaming I/O will be:
>
> page A, offset 0, len 8k
> page A, offset 16k, len 8k
> page A, offset 32k, len 8k
> page A, offset 48k, len 8k
> page B, offset 0, len 8k
>
> This is clearly something PRP list will not handle well. Note that I'm
> not nessecarily saying this is soemthing to optimize for, the more
> interesting case for NVMe really is the vectored direct I/O case.
I'm not really interested in optimising for badly configured RAID setups :-)
But point taken, RAID (and other things) can mess with I/Os between the
page cache and the driver.
next prev parent reply other threads:[~2015-07-30 18:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-27 16:22 SGL support of driver sheng qiu
2015-07-27 16:31 ` Christoph Hellwig
2015-07-27 16:50 ` Keith Busch
2015-07-27 16:57 ` Christoph Hellwig
2015-07-27 17:13 ` Keith Busch
2015-07-28 14:35 ` Matthew Wilcox
2015-07-29 7:55 ` Christoph Hellwig
2015-07-29 14:28 ` Keith Busch
2015-07-30 18:38 ` Matthew Wilcox [this message]
2015-07-31 7:19 ` Christoph Hellwig
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