From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: xen-devel@lists.xensource.com,
Ian Jackson <Ian.Jackson@eu.citrix.com>,
Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Subject: Re: [PATCH 2 of 8] libxl: introduce libxl_set_relative_memory_target
Date: Wed, 01 Sep 2010 14:17:39 -0700 [thread overview]
Message-ID: <4C7EC2F3.3050704@goop.org> (raw)
In-Reply-To: <43844cf2-4c99-448c-a98c-3100baae6dcc@default>
On 09/01/2010 01:03 PM, Dan Magenheimer wrote:
> Indeed, that's what selfballooning does. The xenstore watch
> is irrelevant for selfballooning (though the watch also can be used
> asynchronously for backwards compatibility).
There's no mechanism to make the balloon driver ignore the target watch,
so any updates to xenstore will update the driver's target.
> IMHO, attempts to do memory load balancing externally (e.g. setting
> a memory target from tools in dom0) are doomed to failure. There
> was a discussion of memory "rightsizing" at the recent Linux MM summit;
> this is an almost impossible problem even within a single kernel,
> though there were heuristics discussed as to how to approach it...
> and a better understanding about why in-kernel tmem-ish functionalities
> like cleancache and frontswap are useful for mitigating the problems
> that occur when rightsizing is approximated.
> [...]
> So, frankly, I think the "xm memset" functionality is largely
> useless, but agree that it should be maintained in xl for backwards
> compatibility. But trying to comingle the concepts of maxmem
> and target is a bad idea.
In the general case I think you're probably right (I can't see it being
useful in a VPS hosting service, for example), but there are definitely
special cases where it is useful. Squashing down existing domains to
make room for a new one, for example, or more app-specific uses.
Giving domains some real incentive to be economical with memory would
probably change the landscape a lot. But I don't think there's a real
solution without knowing the specifics of that incentive.
J
next prev parent reply other threads:[~2010-09-01 21:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-27 11:18 [PATCH 2 of 8] libxl: introduce libxl_set_relative_memory_target Stefano Stabellini
2010-08-31 17:25 ` Ian Jackson
2010-09-01 10:55 ` Stefano Stabellini
2010-09-01 18:01 ` Jeremy Fitzhardinge
2010-09-01 20:03 ` Dan Magenheimer
2010-09-01 21:17 ` Jeremy Fitzhardinge [this message]
2010-09-01 21:49 ` Dan Magenheimer
2010-09-02 9:15 ` Stefano Stabellini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4C7EC2F3.3050704@goop.org \
--to=jeremy@goop.org \
--cc=Ian.Jackson@eu.citrix.com \
--cc=dan.magenheimer@oracle.com \
--cc=stefano.stabellini@eu.citrix.com \
--cc=xen-devel@lists.xensource.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.