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From: Sagi Grimberg <sagi@grimberg.me>
To: Logan Gunthorpe <logang@deltatee.com>,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org,
	linux-nvdimm@lists.01.org, linux-block@vger.kernel.org
Cc: "Jens Axboe" <axboe@kernel.dk>,
	"Christian König" <christian.koenig@amd.com>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Steve Wise" <swise@opengridcomputing.com>,
	"Alex Williamson" <alex.williamson@redhat.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Jason Gunthorpe" <jgg@mellanox.com>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Max Gurtovoy" <maxg@mellanox.com>,
	"Christoph Hellwig" <hch@lst.de>
Subject: Re: [PATCH v8 13/13] nvmet: Optionally use PCI P2P memory
Date: Mon, 1 Oct 2018 15:23:25 -0700	[thread overview]
Message-ID: <b790b11f-41df-f495-fdd1-d8bd6d6b7dd6@grimberg.me> (raw)
In-Reply-To: <69cd8aab-b94e-98f5-5397-48bb875e8280@deltatee.com>


>>> +/*
>>> + * If allow_p2pmem is set, we will try to use P2P memory for the SGL lists for
>>> + * Ι/O commands. This requires the PCI p2p device to be compatible with the
>>> + * backing device for every namespace on this controller.
>>> + */
>>> +static void nvmet_setup_p2pmem(struct nvmet_ctrl *ctrl, struct nvmet_req *req)
>>> +{
>>> +	struct nvmet_ns *ns;
>>> +	int ret;
>>> +
>>> +	if (!req->port->use_p2pmem || !req->p2p_client)
>>> +		return;
>>
>> Nit, IMO would be better to check at the call-site, but not a hard
>> must...
> 
> I'd rather keep the logic for whether to enable p2pmem in it's own
> function. nvme_alloc_ctrl() is already very long and complicated.

Fair enough..

>> I still do not fully understand why p2p_dev has to be ctrl-wide and not
>> per namespace. Sorry to keep bringing this up (again). But if people are
>> OK with it then I guess I can stop asking about this...
> 
> Because you never answered my question back in March[1] (which I think
> you've answered below)....

I'm sorry... I lost tracking on this...

>> I think that at some point we said that this looks like it should fall
>> back to host memory for those namespaces.. when we allocate the sgl we
>> already assigned a namespace to the request (nvmet_req_init).
> 
> I did not realize the namespace would be available at this time. I guess
> I can give this a try, but it's going to be a fairly big change from
> what's presented here... Though, I agree it'll probably be an improvement.

Thanks, if it turns out to create to much of a churn, we could defer
that to a later stage, but we can at least document it.
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  reply	other threads:[~2018-10-01 22:23 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-27 16:54 [PATCH v8 00/13] Copy Offload in NVMe Fabrics with P2P PCI Memory Logan Gunthorpe
2018-09-27 16:54 ` [PATCH v8 01/13] PCI/P2PDMA: Support peer-to-peer memory Logan Gunthorpe
2018-09-27 16:54 ` [PATCH v8 02/13] PCI/P2PDMA: Add sysfs group to display p2pmem stats Logan Gunthorpe
2018-09-27 16:54 ` [PATCH v8 03/13] PCI/P2PDMA: Add PCI p2pmem DMA mappings to adjust the bus offset Logan Gunthorpe
2018-09-27 16:54 ` [PATCH v8 04/13] PCI/P2PDMA: Introduce configfs/sysfs enable attribute helpers Logan Gunthorpe
2018-09-27 16:54 ` [PATCH v8 05/13] docs-rst: Add a new directory for PCI documentation Logan Gunthorpe
2018-09-27 16:54 ` [PATCH v8 06/13] PCI/P2PDMA: Add P2P DMA driver writer's documentation Logan Gunthorpe
2018-09-27 16:54 ` [PATCH v8 07/13] block: Add PCI P2P flag for request queue and check support for requests Logan Gunthorpe
2018-09-27 16:54 ` [PATCH v8 08/13] IB/core: Ensure we map P2P memory correctly in rdma_rw_ctx_[init|destroy]() Logan Gunthorpe
2018-09-27 16:54 ` [PATCH v8 09/13] nvme-pci: Use PCI p2pmem subsystem to manage the CMB Logan Gunthorpe
2018-09-27 17:10   ` Keith Busch
2018-09-27 16:54 ` [PATCH v8 10/13] nvme-pci: Add support for P2P memory in requests Logan Gunthorpe
2018-09-27 17:10   ` Keith Busch
2018-09-27 16:54 ` [PATCH v8 11/13] nvme-pci: Add a quirk for a pseudo CMB Logan Gunthorpe
2018-09-27 17:09   ` Keith Busch
2018-09-27 16:54 ` [PATCH v8 12/13] nvmet: Introduce helper functions to allocate and free request SGLs Logan Gunthorpe
2018-09-27 16:54 ` [PATCH v8 13/13] nvmet: Optionally use PCI P2P memory Logan Gunthorpe
2018-09-27 17:12   ` Keith Busch
2018-09-27 17:29     ` Logan Gunthorpe
2018-10-01 21:34   ` Sagi Grimberg
2018-10-01 21:55     ` Logan Gunthorpe
2018-10-01 22:23       ` Sagi Grimberg [this message]
2018-10-01 23:43         ` Logan Gunthorpe

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