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From: Christoph Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>
To: ahmad omary <ahmad151084-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Ahmad Omary <ahmad-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	Leon Romanovsky <leonro-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	Yishai Hadas <yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	Tzahi Oved <tzahio-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	Alex Rosenbaum <Alexr-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	Ariel Levkovich <lariel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	Liran Liss <liranl-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Subject: Re: [RFC] libibverbs IB Device Memory support
Date: Mon, 5 Jun 2017 11:44:00 -0500 (CDT)	[thread overview]
Message-ID: <alpine.DEB.2.20.1706051141230.26831@east.gentwo.org> (raw)
In-Reply-To: <CADWppnpd9Up7wUTxRgSinhgx3kt3+0bKwgt6P_d3CV1oA90isQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Wed, 10 May 2017, ahmad omary wrote:

> We have considered using mmap(), but As the size of device memory may be limited
> ,the way to access it from host cpu may differ from vendor to vendor, due to
> the 4K (page) aligment limitation of mmap() and the need not to directly
> allow user to access the device memory, there is a need for a wrapper access
> methods API that allows allocating and managing chunks that are smaller than
> 4KB and not necessarily aligned to 4KB (page size).

Why are 4k sized chunks a problem given that there are megabytes of memory
in these devices? We are using various adapters already with an mmapped
solution here.

And I would prefer direct user space access to the memory. Fast access to
the data stored in the NIC is important and it would be best not to have
an intermediate layer that requires memcpy.

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  parent reply	other threads:[~2017-06-05 16:44 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-10 11:25 [RFC] libibverbs IB Device Memory support ahmad omary
     [not found] ` <CADWppnpd9Up7wUTxRgSinhgx3kt3+0bKwgt6P_d3CV1oA90isQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-06-05 16:44   ` Christoph Lameter [this message]
     [not found]     ` <alpine.DEB.2.20.1706051141230.26831-wcBtFHqTun5QOdAKl3ChDw@public.gmane.org>
2017-06-05 17:08       ` Leon Romanovsky
     [not found]         ` <20170605170825.GP6868-U/DQcQFIOTAAJjI8aNfphQ@public.gmane.org>
2017-06-05 17:17           ` Jason Gunthorpe
     [not found]             ` <20170605171749.GA20477-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2017-06-05 17:41               ` Leon Romanovsky
     [not found]                 ` <20170605174151.GR6868-U/DQcQFIOTAAJjI8aNfphQ@public.gmane.org>
2017-06-05 22:11                   ` Christoph Lameter
     [not found]                     ` <alpine.DEB.2.20.1706051705350.886-wcBtFHqTun5QOdAKl3ChDw@public.gmane.org>
2017-06-06 11:51                       ` Ahmad Omary
     [not found]                         ` <AM4PR0501MB1956B596450F3BC38806E775C4CB0-dp/nxUn679ggcKT3UpMsY8DSnupUy6xnnBOFsp37pqbUKgpGm//BTAC/G2K4zDHf@public.gmane.org>
2017-06-06 15:25                           ` Liran Liss
2017-06-06 15:30                           ` Christoph Lameter
     [not found]                             ` <alpine.DEB.2.20.1706061022270.16819-wcBtFHqTun5QOdAKl3ChDw@public.gmane.org>
2017-06-08 13:10                               ` Liran Liss
2017-06-06  7:10       ` Christoph Hellwig
2017-06-05 17:20   ` Jason Gunthorpe
     [not found]     ` <20170605172058.GB20477-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2017-06-06  5:52       ` Leon Romanovsky
     [not found]         ` <20170606055229.GT6868-U/DQcQFIOTAAJjI8aNfphQ@public.gmane.org>
2017-06-06  6:31           ` Leon Romanovsky
2017-06-06 16:34           ` Jason Gunthorpe
2017-06-06  7:35   ` Sagi Grimberg
     [not found]     ` <46b1a06d-5936-799c-7743-097c579971ef-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org>
2017-06-06 16:49       ` Logan Gunthorpe

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