On Tue, Dec 12, 2006 at 06:25:25PM +0000, Daniel P. Berrange wrote:
> The changeset '12803:df5fa63490f4da7b65c56087a68783dbcb7944f8' added a new
> hypercall XENMEM_set_memory_map for specifying the e820 mapping. There was
> a small bug in the userspace side of this change though - the e820 mapping
> was specified based on the 'memory_static_min' domain info parameter which
> means the memory map size is clamped to the value 'memory' config option.
>
> What we actually want is to setup the e820 map limit based on 'maxmem'
> config option, so that we can balloon up the guest to its max limit.
>
> eg
> If we boot with 'memory=400' and 'maxmem=800', the e820 map should be
> set to 800 MB, and the guest should allocate only 400 MB at startup.
> It should then be possible to use 'xm mem-set' after boot to assgin
> upto this 800 MB.
>
> Thus, the attached patch fixed the image.py class to setup the e820 mapping
> based on 'memory_static_max' which is in turn based on 'maxmem'. Booting
> with this patch I can verify that the guest kernel sees a 800 MB e820 map,
> so this fixes the initial problem.
>
> There appears to be a second issue somewhere in the stack though, because
> even if do 'xm mem-set <domid> 600', while the ballon driver in the guest
> will see the 600 MB target, it will still never try to allocate its
> increased target.
Turns out this was a bug introduced in the refactoring of memory config
parameters from Xen API work. The memory & memmax parameters were getting
initialized the wrong way around. With this fixed & the e820 map fix,
memory ballooning works perfectly:
# xm create demo
Using config file "/etc/xen/demo".
Going to boot Fedora Core (2.6.18-1.2769.2.2.el5xen)
kernel: /vmlinuz-2.6.18-1.2769.2.2.el5xen
initrd: /initrd-2.6.18-1.2769.2.2.el5xen.img
Started domain demo
# xm list demo
Name ID Mem VCPUs State Time(s)
demo 16 410 2 -b---- 0.4
# xm mem-set demo 600
# xm list demo
Name ID Mem VCPUs State Time(s)
demo 16 600 2 -b---- 4.2
Attaching an updated patch which fixes both the memory ballooning issues
in one go
Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
Regards,
Dan.
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xen-mem-e820-size-2.patch
Description: Text document
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