From: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
To: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
Cc: dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
infinipath-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org,
ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org,
roid-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org,
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
eli-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org,
target-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org
Subject: Re: [PATCH V6 9/9] isert: Support iWARP transports using FRMRs
Date: Fri, 24 Jul 2015 16:38:35 -0600 [thread overview]
Message-ID: <20150724223835.GA29064@obsidianresearch.com> (raw)
In-Reply-To: <00ee01d0c65d$a1e03cf0$e5a0b6d0$@opengridcomputing.com>
On Fri, Jul 24, 2015 at 05:11:04PM -0500, Steve Wise wrote:
> By the way, just to be clear: If you use a FRWR, you by definition
> only have one SGE entry as the result of the registration. So
> regardless of what a device/protocol can do with the destination SGE
> of an RDMA READ operation, if you use FRWR to register the
> destination region, you need only 1 SGE in the RDMA READ WR.
FRWR's have horrible restrictions on the scatterlist. To realize
arbitrary scatterlists requires multiple MRs, and thus multiple SGE
entries.
The warning is for a reader who might be familiar with IB and think
iWarp simply needs to have a MR wrapped around the memory and assume
gaps/etc can be supported through a s/g list, like IB can.
Jason
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WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Steve Wise <swise@opengridcomputing.com>
Cc: dledford@redhat.com, infinipath@intel.com, sagig@mellanox.com,
ogerlitz@mellanox.com, roid@mellanox.com,
linux-rdma@vger.kernel.org, eli@mellanox.com,
target-devel@vger.kernel.org, linux-nfs@vger.kernel.org,
bfields@fieldses.org
Subject: Re: [PATCH V6 9/9] isert: Support iWARP transports using FRMRs
Date: Fri, 24 Jul 2015 16:38:35 -0600 [thread overview]
Message-ID: <20150724223835.GA29064@obsidianresearch.com> (raw)
In-Reply-To: <00ee01d0c65d$a1e03cf0$e5a0b6d0$@opengridcomputing.com>
On Fri, Jul 24, 2015 at 05:11:04PM -0500, Steve Wise wrote:
> By the way, just to be clear: If you use a FRWR, you by definition
> only have one SGE entry as the result of the registration. So
> regardless of what a device/protocol can do with the destination SGE
> of an RDMA READ operation, if you use FRWR to register the
> destination region, you need only 1 SGE in the RDMA READ WR.
FRWR's have horrible restrictions on the scatterlist. To realize
arbitrary scatterlists requires multiple MRs, and thus multiple SGE
entries.
The warning is for a reader who might be familiar with IB and think
iWarp simply needs to have a MR wrapped around the memory and assume
gaps/etc can be supported through a s/g list, like IB can.
Jason
next prev parent reply other threads:[~2015-07-24 22:38 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-24 16:18 [PATCH V6 0/9] iSER support for iWARP Steve Wise
2015-07-24 16:18 ` Steve Wise
[not found] ` <20150724161331.25617.8475.stgit-PBeJgSbIpn97NCTnQtmixQ@public.gmane.org>
2015-07-24 16:18 ` [PATCH V6 1/9] RDMA/iser: Limit sg tablesize and max_sectors to device fastreg max depth Steve Wise
2015-07-24 16:18 ` Steve Wise
[not found] ` <20150724161820.25617.63886.stgit-PBeJgSbIpn97NCTnQtmixQ@public.gmane.org>
2015-07-24 16:41 ` Jason Gunthorpe
2015-07-24 16:41 ` Jason Gunthorpe
2015-07-24 18:40 ` Steve Wise
2015-07-24 18:40 ` Steve Wise
2015-07-24 19:14 ` Jason Gunthorpe
2015-07-26 9:58 ` Sagi Grimberg
2015-07-26 9:57 ` Sagi Grimberg
2015-07-26 9:57 ` Sagi Grimberg
2015-07-24 16:18 ` [PATCH V6 2/9] mlx4, mlx5, mthca: Expose max_sge_rd correctly Steve Wise
2015-07-24 16:18 ` Steve Wise
2015-07-24 16:18 ` [PATCH V6 3/9] ipath,qib: " Steve Wise
2015-07-24 16:18 ` Steve Wise
2015-07-24 16:18 ` [PATCH V6 4/9] svcrdma: Use max_sge_rd for destination read depths Steve Wise
2015-07-24 16:18 ` Steve Wise
[not found] ` <20150724161837.25617.48584.stgit-PBeJgSbIpn97NCTnQtmixQ@public.gmane.org>
2015-07-24 18:51 ` Steve Wise
2015-07-24 18:51 ` Steve Wise
2015-07-26 9:58 ` Sagi Grimberg
[not found] ` <55B4AF63.3040108-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
2015-07-26 10:42 ` Christoph Hellwig
2015-07-26 10:42 ` Christoph Hellwig
2015-07-24 16:18 ` [PATCH V6 6/9] isert: Rename IO functions to more descriptive names Steve Wise
2015-07-24 16:18 ` Steve Wise
[not found] ` <20150724161848.25617.26092.stgit-PBeJgSbIpn97NCTnQtmixQ@public.gmane.org>
2015-07-26 10:08 ` Sagi Grimberg
2015-07-26 10:08 ` Sagi Grimberg
[not found] ` <55B4B190.7070305-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
2015-07-26 10:43 ` Christoph Hellwig
2015-07-26 10:43 ` Christoph Hellwig
[not found] ` <20150726104328.GB18944-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-07-26 11:00 ` Sagi Grimberg
2015-07-26 11:00 ` Sagi Grimberg
2015-07-26 15:53 ` Christoph Hellwig
2015-07-26 16:44 ` Sagi Grimberg
[not found] ` <55B4BDE3.8040801-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
2015-07-26 17:32 ` Steve Wise
2015-07-26 17:32 ` Steve Wise
2015-07-26 17:40 ` Sagi Grimberg
[not found] ` <55B51B7A.8030008-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
2015-07-26 20:15 ` Steve Wise
2015-07-26 20:15 ` Steve Wise
2015-07-26 20:17 ` Steve Wise
2015-07-26 20:17 ` Steve Wise
[not found] ` <55B5404F.5040404-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
2015-07-27 21:45 ` Steve Wise
2015-07-27 21:45 ` Steve Wise
2015-08-03 19:32 ` Steve Wise
2015-08-03 19:32 ` Steve Wise
2015-08-04 17:26 ` Sagi Grimberg
[not found] ` <55C0F5B7.4040100-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
2015-08-04 17:44 ` Steve Wise
2015-08-04 17:44 ` Steve Wise
2015-08-05 21:23 ` Steve Wise
2015-08-05 21:23 ` Steve Wise
2015-08-06 15:37 ` Sagi Grimberg
2015-08-06 15:37 ` Sagi Grimberg
[not found] ` <55C37F43.6080106-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
2015-08-12 22:15 ` Steve Wise
2015-08-12 22:15 ` Steve Wise
2015-08-13 13:09 ` Sagi Grimberg
2015-07-24 16:18 ` [PATCH V6 5/9] RDMA/isert: Limit read depth based on the device max_sge_rd capability Steve Wise
2015-07-24 16:18 ` [PATCH V6 7/9] isert: Use the device's max fastreg page list depth Steve Wise
2015-07-24 16:18 ` [PATCH V6 8/9] isert: Use local_dma_lkey whenever possible Steve Wise
[not found] ` <20150724161859.25617.17286.stgit-PBeJgSbIpn97NCTnQtmixQ@public.gmane.org>
2015-07-24 16:49 ` Jason Gunthorpe
2015-07-24 16:49 ` Jason Gunthorpe
[not found] ` <20150724164909.GB25480-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2015-07-24 18:41 ` Steve Wise
2015-07-24 18:41 ` Steve Wise
2015-07-24 16:19 ` [PATCH V6 9/9] isert: Support iWARP transports using FRMRs Steve Wise
2015-07-24 16:57 ` Jason Gunthorpe
2015-07-24 18:48 ` Steve Wise
2015-07-24 18:48 ` Steve Wise
2015-07-24 19:24 ` Jason Gunthorpe
2015-07-24 19:24 ` Jason Gunthorpe
2015-07-24 19:57 ` Steve Wise
2015-07-24 19:57 ` Steve Wise
2015-07-24 22:11 ` Steve Wise
2015-07-24 22:11 ` Steve Wise
2015-07-24 22:38 ` Jason Gunthorpe [this message]
2015-07-24 22:38 ` Jason Gunthorpe
[not found] ` <20150724192411.GC26225-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2015-07-26 10:23 ` Sagi Grimberg
2015-07-26 10:23 ` Sagi Grimberg
2015-07-27 17:07 ` Jason Gunthorpe
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