From: minwoo.im.dev@gmail.com (Minwoo Im)
Subject: nvme-pci: about page_size of DMA pool
Date: Thu, 22 Feb 2018 22:26:58 +0900 [thread overview]
Message-ID: <e2823a5e-38df-2002-8374-0408adfb1abd@gmail.com> (raw)
In-Reply-To: <20180220160603.GB7076@localhost.localdomain>
On 02/21/2018 01:06 AM, Keith Busch wrote:
>> Q1. Should dev->prp_page_pool be created with dev->ctrl.page_size
>> instead of PAGE_SIZE?
>
> Yeah, the current method looks like it may potentially be over-allocating
> some memory for very large IO transfers. The size of the "large" pool
> ought to be the same as ctrl.page_size.
>
>>
>> Q2. Is there any special reason why page_shift in nvme_enable_ctrl()
>> is hard-coded to 12, not PAGE_SHIFT?
>
> Some CPU architectures have different alignment when comparing DMA mapped
> addresses with the virual address, so we have to go to the lowest common
> denominator. Previous discussion here:
>
> http://lists.infradead.org/pipermail/linux-nvme/2015-October/002893.html
>
Thanks for your kind response, Keith. :)
prev parent reply other threads:[~2018-02-22 13:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-18 7:52 nvme-pci: about page_size of DMA pool Minwoo Im
2018-02-20 16:06 ` Keith Busch
2018-02-22 13:26 ` Minwoo Im [this message]
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