Re: [PATCH -V6 07/14] memcg: Add HugeTLB extension

[David Rientjes <rientjes@google.com>]

On Fri, 15 Jun 2012, Aditya Kali wrote:

> Based on the usecase at Google, I see a definite value in including
> hugepage usage in memory.usage_in_bytes as well and having a single
> limit for memory usage for the job. Our jobs wants to specify only one
> (total) memory limit (including slab usage, and other kernel memory
> usage, hugepages, etc.).
> 
> The hugepage/smallpage requirements of the job vary during its
> lifetime. Having two different limits means less flexibility for jobs
> as they now have to specify their limit as (max_hugepage,
> max_smallpage) instead of max(hugepage + smallpage). Two limits
> complicates the API for the users and requires them to over-specify
> the resources.
> 

If a large number of hugepages, for example, are allocated on the command 
line because there's a lower success rate of dynamic allocation due to 
fragmentation, with your suggestion it would no longer allow the admin to 
restrict the use of those hugepages to only a particular set of tasks.  
Consider especially 1GB hugepagez on x86, your suggestion would treat a 
single 1GB hugepage which cannot be freed after boot exactly the same as 
using 1GB of memory which is obviously not the desired behavior of any 
hugetlb controller.

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