Re: [Xen-devel] Restart domU failure (memory allocation issue)

[Andrii Anisov <andrii.anisov@xxxxxxxxxxxxxxx>]

Julien,

I gave a try on Xen 4.4 with normal guest (e.g without the 1:1 mapping) and I don't find any memory leaks. How do you create the 1:1 mapping for the guest?

The way we get 1:1 mapping is pretty tricky.

We have a patch to allocate DomU space as a one multipage section with the order enough for requested size. While we place all the XEN stuff after the first gigabyte of RAM, we do have the only 1GB extent at address 0x80000000 for our Android. 

We do work to get rid of this dirty hack. But still have a lot of things to do with GPU and IPU.

From the investigations done by Oleksandr it seems to me that some mappings done for so called kernel segment by xc_dom_alloc_segment() are left in dom0 space.

Andrii Anisov | Software Engineer
GlobalLogic

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On Thu, Mar 13, 2014 at 9:48 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:

(Adding ARM people in CC)

On 13/03/14 18:33, Oleksandr Tyshchenko wrote:

Hello, all.

Hello Oleksandr,

I am working with DRA7 (OMAP5) platform and I am using XEN 4.4 and
Kernel 3.8 for both domains.
As we still have 1:1 mapping for domU we need to allocate memory (1024
MB in our case) for it at one chunk.

The issue is that I can't create domain again after destroying it (I
am destroying domain by a "xl destroy" command) because we no longer
have contiguous memory region and as result allocation failed.

It seems, we have memory leak. I see that not all memory is freed
after domain destroy.
I see that some pages (which were allocated for kernel segment) don't
returned to the heap.

I gave a try on Xen 4.4 with normal guest (e.g without the 1:1 mapping) and I don't find any memory leaks. How do you create the 1:1 mapping for the guest?

/ # xl list
Name                                        ID   Mem VCPUs      State   Time(s)
Domain-0                                     0   128     2     r-----       4.1
(null)                                       1     5     2     --p--d       0.9

It seems that your domain is not completely destroyed. It may be because some pages still belongs to the domain.

Xen will free a page only when the reference count is 0, do you have keep some mapping in dom0? (for instance in libxl).

Regards,

--
Julien Grall

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