From: Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
To: Jason Gunthorpe
<jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>,
Matthew Wilcox <willy-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: Stephen Bates <stephen.bates-PwyqCcigF0Q@public.gmane.org>,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org,
javier-rmLALz0KWFtWk0Htik3J/w@public.gmane.org,
sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org,
leonro-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org,
artemyko-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org,
hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org
Subject: Re: [PATCH RFC 1/1] Add support for ZONE_DEVICE IO memory with struct pages.
Date: Thu, 17 Mar 2016 17:18:11 +0200 [thread overview]
Message-ID: <56EACAB3.5070301@mellanox.com> (raw)
In-Reply-To: <20160314215708.GA7282-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
On 3/14/2016 11:57 PM, Jason Gunthorpe wrote:
> The other issue is that the fencing mechanism RDMA uses to create
> ordering with system memory is not good enough to fence peer-peer
> transactions in the general case. It is only possibly good enough if
> all the transactions run through the root complex.
Are you sure this is a problem? I'm not sure it is clear in the PCIe
specs, but I thought that for transactions that are not relaxed-ordered
and don't use ID-based ordering, a PCIe switch must prevent reads and
writes from passing writes. I assume this is true even when the requestor
ID is different because IDO relaxes these constraints specifically
for transactions coming from different requestor IDs.
Regards,
Haggai
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WARNING: multiple messages have this Message-ID (diff)
From: Haggai Eran <haggaie@mellanox.com>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
Matthew Wilcox <willy@linux.intel.com>
Cc: Stephen Bates <stephen.bates@pmcs.com>,
linux-mm@kvack.org, linux-rdma@vger.kernel.org,
linux-nvdimm@ml01.01.org, javier@cnexlabs.com,
sagig@mellanox.com, leonro@mellanox.com, artemyko@mellanox.com,
hch@infradead.org
Subject: Re: [PATCH RFC 1/1] Add support for ZONE_DEVICE IO memory with struct pages.
Date: Thu, 17 Mar 2016 17:18:11 +0200 [thread overview]
Message-ID: <56EACAB3.5070301@mellanox.com> (raw)
In-Reply-To: <20160314215708.GA7282@obsidianresearch.com>
On 3/14/2016 11:57 PM, Jason Gunthorpe wrote:
> The other issue is that the fencing mechanism RDMA uses to create
> ordering with system memory is not good enough to fence peer-peer
> transactions in the general case. It is only possibly good enough if
> all the transactions run through the root complex.
Are you sure this is a problem? I'm not sure it is clear in the PCIe
specs, but I thought that for transactions that are not relaxed-ordered
and don't use ID-based ordering, a PCIe switch must prevent reads and
writes from passing writes. I assume this is true even when the requestor
ID is different because IDO relaxes these constraints specifically
for transactions coming from different requestor IDs.
Regards,
Haggai
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
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next prev parent reply other threads:[~2016-03-17 15:18 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-14 18:14 [PATCH RFC 1/1] Add support for ZONE_DEVICE IO memory with struct pages Stephen Bates
2016-03-14 21:23 ` Matthew Wilcox
2016-03-14 21:23 ` Matthew Wilcox
2016-03-14 21:23 ` Matthew Wilcox
[not found] ` <20160314212344.GC23727-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2016-03-14 21:57 ` Jason Gunthorpe
2016-03-14 21:57 ` Jason Gunthorpe
2016-03-15 4:09 ` Logan Gunthorpe
[not found] ` <56E78B08.8050205-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
2016-03-15 17:00 ` Stephen Bates
2016-03-15 17:00 ` Stephen Bates
[not found] ` <20160314215708.GA7282-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2016-03-17 15:18 ` Haggai Eran [this message]
2016-03-17 15:18 ` Haggai Eran
[not found] ` <56EACAB3.5070301-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2016-03-17 16:11 ` Jason Gunthorpe
2016-03-17 16:11 ` Jason Gunthorpe
2016-03-21 19:25 ` Stephen Bates
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