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From: Or Gerlitz <ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
To: Alexander Duyck
	<alexander.h.duyck-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: Or Gerlitz <or.gerlitz-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	"Michael S. Tsirkin"
	<mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Roland Dreier <roland-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
	Yan Burman <yanb-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Paolo Bonzini <pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Asias He <asias-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: decent performance drop for SCSI LLD / SAN initiator when iommu is turned on
Date: Tue, 7 May 2013 15:12:29 +0300	[thread overview]
Message-ID: <5188EFAD.50708@mellanox.com> (raw)
In-Reply-To: <5188304E.9050603-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

On 07/05/2013 01:35, Alexander Duyck wrote:
> The Tx path ends up taking a performance hit if IOMMU is enabled.  It
> just isn't as severe due to things like TSO.

In testing done by some Mellanox folks I think they see major penalty on 
the RX side, but hardly
nothing on the TX side, I'll check that.

> One way to work around the performance penalty is to allocate bounce
> buffers and just leave them static mapped.  Then you can simply memcpy
> the data to the buffers and avoid the locking overhead of
> allocating/freeing IOMMU resources.  It consumes more memory but works
> around the IOMMU limitations.

I don't think can be applicable approach to fast networking/storage drivers.

Or.
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  parent reply	other threads:[~2013-05-07 12:12 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-05-01 23:11 decent performance drop for SCSI LLD / SAN initiator when iommu is turned on Or Gerlitz
     [not found] ` <CAJZOPZJ8eF-Q+WFzA-_vvzkpSb41PQjKFo27_Wi3McUccOqs9A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-05-02  0:13   ` Roland Dreier
2013-05-02  1:56   ` Michael S. Tsirkin
     [not found]     ` <20130502015603.GC26105-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-05-02 14:13       ` Yan Burman
     [not found]         ` <0EE9A1CDC8D6434DB00095CD7DB873462CF9D73E-fViJhHBwANKuSA5JZHE7gA@public.gmane.org>
2013-05-03 19:40           ` Don Dutile
     [not found]             ` <518412AC.3070507-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-05-05 14:06               ` Yan Burman
2013-05-06 21:39       ` Or Gerlitz
     [not found]         ` <CAJZOPZLWgXNCEpZjzuizVGPEVPg1G+cHh373ZCoumMx9eAabvQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-05-06 22:35           ` Alexander Duyck
     [not found]             ` <5188304E.9050603-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2013-05-07 12:12               ` Or Gerlitz [this message]
2013-05-07 12:22               ` Michael S. Tsirkin
     [not found]                 ` <20130507122235.GA21361-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-05-07 14:50                   ` Or Gerlitz

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