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Re: [Xen-devel] [PATCH] xenpaging: libxl support

To: Olaf Hering <olaf@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] xenpaging: libxl support
From: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Date: Tue, 27 Sep 2011 17:48:30 +0100
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Olaf Hering writes ("[Xen-devel] [PATCH] xenpaging: libxl support"):
> The patch adds four new config options:
> xenpaging=<int> , the number of pages to page-out
...
> +libxl_xenpaging_info = Struct("xenpaging_info",[
> +    ("xenpaging",                 integer,    False, "number of pages"),
...
> +        if (!xlu_cfg_get_long (config, "xenpaging", &l))
> +            xp_info->xenpaging = l;

The config file setting should be a number of megabytes, just like
"memory", "maxmem", etc., not a number of pages.  And at the libxl
interface it should be a number of kilobytes like max_memkb et al.

Also as I said at the hackathon, I think that we need a more
sophisticated approach to the interaction with ballooning.  I would
like to see the argument to the xenpaging daemon not be a target
number of pages to page out, but rather for it to be a total memory
usage target.

The effect of this would be that you could tell a guest to balloon
down, but also tell xenpaging to page it out, and balance between
ballooning and paging is then up to the guest.

> +static int libxl__create_xenpaging(libxl__gc *gc, char *dom_name, uint32_t 
> domid, libxl_xenpaging_info *xp_info)
> +{
> + [a lot of stuff]

Can any of this be factored out and made common with the device model
creation ?

Also:
  - what deletes the logfile, if anything ?
  - will the xenpaging daemon automatically exit if the domain dies ?

Ian.

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