[Devel] Re: [ckrm-tech] [PATCH] BC: resource beancounters (v4) (added user memory)

[Pavel Emelianov]

Chandra Seetharaman wrote:

[snip]
>>>> The question is - whether web server is multithreaded or not...
>>>> If it is not - then no problem here, you can change current
>>>> context and new resources will be charged accordingly.
>>>>
>>>> And current BC code is _able_ to handle it with _minor_ changes.
>>>> (One just need to save bc not on mm struct, but rather on vma struct
>>>> and change mm->bc on set_bc_id()).
>>>>
>>>> However, no one (can some one from CKRM team please?) explained so far
>>>> what to do with threads. Consider the following example.
>>>>
>>>> 1. Threaded web server spawns a child to serve a client.
>>>> 2. child thread touches some pages and they are charged to child BC
>>>>    (which differs from parent's one)
>>>> 3. child exits, but since its mm is shared with parent, these pages
>>>>    stay mapped and charged to child BC.
>>>>
>>>> So the question is:  what to do with these pages?
>>>> - should we recharge them to another BC?
>>>> - leave them charged?
>>>>     
>>>>         
>>> Leave them charged. It will be charged to the appropriate UBC when they
>>> touch it again.
>>>   
>>>       
>> Do you mean that page must be re-charged each time someone touches it?
>>     
>
> What I meant is that to leave them charged, and if when they are
> ummapped and mapped later, charge it to the appropriate BC.
>   
In this case multithreaded apache that tries to serve each domain in
separate BC will fill the memory with BC-s, held by pages allocated
and mapped in threads.