From: Olaf Hering <olaf@aepfle.de>
To: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: xen-devel@lists.xensource.com,
Ian Campbell <Ian.Campbell@citrix.com>,
Konrad Wilk <konrad.wilk@oracle.com>,
Lars Kurth <lars.kurth.xen@gmail.com>,
Kurt Hackel <kurt.hackel@oracle.com>, Tim Deegan <tim@xen.org>,
Andres Lagar-Cavilla <andres@lagarcavilla.org>
Subject: Re: Pointed questions re Xen memory overcommit
Date: Wed, 29 Feb 2012 11:43:08 +0100 [thread overview]
Message-ID: <20120229104308.GA23724@aepfle.de> (raw)
In-Reply-To: <104d17ef-192d-4a13-9d19-b27a58f04384@default>
On Mon, Feb 27, Dan Magenheimer wrote:
> > From: Olaf Hering [mailto:olaf@aepfle.de]
> > To me memory overcommit means swapping, which is what xenpaging does:
> > turn the whole guest gfn range into some sort of virtual memory,
> > transparent to the guest.
> >
> > xenpaging is the red emergency knob to free some host memory without
> > caring about the actual memory constraints within the paged guests.
>
> Sure, but the whole point of increasing RAM in one or more guests
> is to increase performance, and if overcommitting *always* means
> swapping, why would anyone use it?
The usage patterns depend on the goal. As I wrote, swapping frees host
memory so it can be used for something else, like starting yet another
guest on the host.
Olaf
next prev parent reply other threads:[~2012-02-29 10:43 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-24 20:53 Pointed questions re Xen memory overcommit Dan Magenheimer
2012-02-24 21:42 ` Olaf Hering
2012-02-27 23:40 ` Dan Magenheimer
2012-02-28 13:54 ` George Dunlap
2012-02-28 21:32 ` Dan Magenheimer
2012-02-29 10:43 ` Olaf Hering [this message]
2012-02-29 17:26 ` Dan Magenheimer
2012-02-29 18:00 ` Andres Lagar-Cavilla
2012-02-29 18:31 ` Dan Magenheimer
2012-02-29 19:11 ` George Dunlap
2012-02-29 20:26 ` Dan Magenheimer
2012-03-01 16:08 ` George Dunlap
2012-03-01 20:34 ` Dan Magenheimer
2012-02-29 19:22 ` Olaf Hering
2012-02-29 20:30 ` Dan Magenheimer
2012-02-29 20:38 ` Olaf Hering
2012-02-27 19:51 ` Tim Deegan
2012-02-27 23:50 ` Dan Magenheimer
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