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From: Bart Van Assche <bart.vanassche-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>
To: Jason Gunthorpe
	<jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>,
	Tom Talpey <tom-CLs1Zie5N5HQT0dZR+AlfA@public.gmane.org>
Cc: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
	Linux NFS Mailing List
	<linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v1 00/16] NFS/RDMA patches proposed for 4.1
Date: Wed, 6 May 2015 09:01:07 +0200	[thread overview]
Message-ID: <5549BC33.30905@sandisk.com> (raw)
In-Reply-To: <20150505223855.GA7696-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>

On 05/06/15 00:38, Jason Gunthorpe wrote:
> Heck, on modern systems 100% of these requirements can be solved just
> by using the IOMMU. No need for the HCA at all. (HCA may be more
> performant, of course)

Hello Jason,

Any performance tests I have run so far with the IOMMU enabled show much 
worse results than the same test with the IOMMU disabled. The perf tool 
learned me that this performance difference is due to lock contention 
caused by the IOMMU kernel code. I have not yet tried to verify whether 
this is an implementation issue or something fundamental.

This is why I'm not enthusiast about any approach that relies on the 
IOMMU being enabled.

Bart.

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  parent reply	other threads:[~2015-05-06  7:01 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20150313211124.22471.14517.stgit@manet.1015granger.net>
     [not found] ` <20150313211124.22471.14517.stgit-FYjufvaPoItvLzlybtyyYzGyq/o6K9yX@public.gmane.org>
2015-05-05 15:44   ` [PATCH v1 00/16] NFS/RDMA patches proposed for 4.1 Christoph Hellwig
     [not found]     ` <20150505154411.GA16729-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-05-05 16:04       ` Chuck Lever
     [not found]         ` <5E1B32EA-9803-49AA-856D-BF0E1A5DFFF4-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
2015-05-05 17:25           ` Christoph Hellwig
     [not found]             ` <20150505172540.GA19442-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-05-05 18:14               ` Tom Talpey
     [not found]                 ` <55490886.4070502-CLs1Zie5N5HQT0dZR+AlfA@public.gmane.org>
2015-05-05 19:10                   ` Christoph Hellwig
     [not found]                     ` <20150505191012.GA21164-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-05-05 20:57                       ` Tom Talpey
     [not found]                         ` <55492ED3.7000507-CLs1Zie5N5HQT0dZR+AlfA@public.gmane.org>
2015-05-05 21:06                           ` Christoph Hellwig
     [not found]                             ` <20150505210627.GA5941-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-05-05 21:32                               ` Tom Talpey
     [not found]                                 ` <554936E5.80607-CLs1Zie5N5HQT0dZR+AlfA@public.gmane.org>
2015-05-05 22:38                                   ` Jason Gunthorpe
     [not found]                                     ` <20150505223855.GA7696-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2015-05-06  0:16                                       ` Tom Talpey
     [not found]                                         ` <55495D41.5090502-CLs1Zie5N5HQT0dZR+AlfA@public.gmane.org>
2015-05-06 16:20                                           ` Jason Gunthorpe
2015-05-06  7:01                                       ` Bart Van Assche [this message]
     [not found]                                         ` <5549BC33.30905-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>
2015-05-06 16:38                                           ` Jason Gunthorpe
2015-05-06  7:33                                   ` Christoph Hellwig
2015-05-06  7:09                               ` Bart Van Assche
     [not found]                                 ` <5549BE30.8020505-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>
2015-05-06  7:29                                   ` Christoph Hellwig
2015-05-06 12:15               ` Sagi Grimberg
2015-03-13 21:26 Chuck Lever

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