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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: xen-devel@lists.xenproject.org,
	Paul Durrant <paul.durrant@citrix.com>,
	Wei Liu <wei.liu2@citrix.com>
Subject: Re: [PATCH v2 3/5] tools/libxendevicemodel: extract functions and add a compat layer
Date: Wed, 22 Feb 2017 15:27:00 +0000	[thread overview]
Message-ID: <2855ff28-b8b9-4548-2178-c82be26c3578@citrix.com> (raw)
In-Reply-To: <22701.43118.14141.591086@mariner.uk.xensource.com>

On 22/02/17 15:04, Ian Jackson wrote:
> Andrew Cooper writes ("Re: [Xen-devel] [PATCH v2 3/5] tools/libxendevicemodel: extract functions and add a compat layer"):
>> On 22/02/17 14:37, Ian Jackson wrote:
>>> Is the bitmap copied in each dmop call ?
>> Yes, and hence...
> Oh!
>
> I had assumed that this wouldn't be the case because it would
> obviously be slow.
>
>> ... one optimisation I want to do in the future is for the DM to be able
>> to make a Read-only mapping of Xens logdirty bitmap, so the bitmap can
>> be passed by shared memory rather than memcpy(), because I expect it
>> would be rather more efficient during some of the time-sensitive bits of
>> live migrate.
> Well, err, yes.
>
> (What about the ioreq ring?)

That is a piece of shared memory.

But shared memory is not interesting to DMOP.  You already *must* defer
to your kernel to create the shared memory in the first place, so the
resulting pointer is definitely ok as far as the kernel is concerned.

~Andrew

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  reply	other threads:[~2017-02-22 15:27 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-22 13:27 [PATCH v2 0/5] tools/libxendevicemodel Paul Durrant
2017-02-22 13:27 ` [PATCH v2 1/5] tools/libxenctrl: fix error check after opening libxenforeignmemory Paul Durrant
2017-02-22 14:09   ` Wei Liu
2017-04-05 13:25     ` Ian Jackson
2017-02-22 14:09   ` Ian Jackson
2017-02-22 13:27 ` [PATCH v2 2/5] tools/libxendevicemodel: introduce the new library Paul Durrant
2017-02-22 14:11   ` Ian Jackson
2017-02-22 13:27 ` [PATCH v2 3/5] tools/libxendevicemodel: extract functions and add a compat layer Paul Durrant
2017-02-22 14:20   ` Ian Jackson
2017-02-22 14:33     ` Andrew Cooper
2017-02-22 14:37       ` Ian Jackson
2017-02-22 14:41         ` Andrew Cooper
2017-02-22 15:04           ` Ian Jackson
2017-02-22 15:27             ` Andrew Cooper [this message]
2017-02-22 13:27 ` [PATCH v2 4/5] tools/libxendevicemodel: introduce a Linux-specific implementation Paul Durrant
2017-02-22 14:22   ` Ian Jackson
2017-02-22 13:27 ` [PATCH v2 5/5] tools/libxendevicemodel: add a call to restrict the handle Paul Durrant
2017-02-22 14:22   ` Ian Jackson

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