Re: [MirageOS-devel] Memory exhaustion in Mirage

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

The actual definition of these functions is probably in the 
mirage/mirage-platform repository at the moment.  Look in the xen/ subdirectory 
and grep for the C file that contains it.

We can migrate this library to use xen_cflags and avoid the need for this 
repetition quite soon as well.  The build hacks are gradually being undone!

-anil

> On 19 Dec 2014, at 09:25, Anil Madhavapeddy <anil@xxxxxxxxxx> wrote:
> 
> CCing the list.
> 
>> On 19 Dec 2014, at 08:49, Masoud Koleini <masoud.koleini@xxxxxxxxxxxxxxxx> 
>> wrote:
>> 
>> I have added the function to stub_alloc_pages.c and defined it as external 
>> function in io_page.ml. No problem in installing io_page, but when compiling 
>> the program, I receive the error:
>> 
>> undefined reference to `caml_dealloc_page'
>> 
>> how do you think I can fix it?
>> 
>> Thanks.
>> 
>> On 18/12/14 13:46, Anil Madhavapeddy wrote:
>>> Not at the moment, although we could easily add an explicit deallocator into
>>> Io_page.  You need to very careful that the page is not used after its 
>>> lifetime,
>>> so more pool-based abstractions are preferred (where the pages are recycled 
>>> into
>>> an OCaml-managed data structure and reused rather than GCed).
>>> 
>>> You should be able to pump up the amount of RAM the VM gets temporarily to 
>>> 4GB
>>> or so -- if the page allocator still remains low, then it's unlikely to be 
>>> a GC
>>> issue and an actual leak somewhere due to holding onto references and 
>>> keeping
>>> the page live.
>>> 
>>> -anil
>>> 
>>>> On 18 Dec 2014, at 05:41, Masoud Koleini <masoud.koleini@xxxxxxxxxxxxxxxx> 
>>>> wrote:
>>>> 
>>>> Is it possible to deallocate an Io_page after packet is send, not to wait 
>>>> for GC?
>>>> 
>>>> On 16/12/14 23:45, Anil Madhavapeddy wrote:
>>>>> On 16 Dec 2014, at 15:23, Masoud Koleini 
>>>>> <masoud.koleini@xxxxxxxxxxxxxxxx> wrote:
>>>>>> I am wondering if the following issue is already addressed:
>>>>>> 
>>>>>> https://github.com/mirage/mirage-tcpip/issues/33
>>>>>> 
>>>>>> https://lists.cam.ac.uk/pipermail/cl-mirage/2013-August/msg00104.html
>>>>>> 
>>>>> It probably still happens at 64MB of RAM -- it requires some code to 
>>>>> adjust
>>>>> the GC parameters in the OCaml runtime to trigger a collection more often.
>>>>> It should be harmless however, since (as the bug report observes), a 
>>>>> failure
>>>>> to allocate an Io_page results in a GC compaction that frees up memory so
>>>>> that the allocation eventually succeeds.
>>>>> 
>>>>> Any particular reason for asking -- is the bug affecting your switch 
>>>>> somehow?
>>>>> 
>>>>> -anil
>>>> 
>>>> 
>>>> 
>>>> 
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>> 
>> 
>> 
>> 
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