Re: [PATCH 0/4] [hugetlb] Dynamic huge page pool resizing

[Adam Litke <agl@us.ibm.com>]

On Tue, 2007-09-25 at 16:52 +0530, Balbir Singh wrote:
> Adam Litke wrote:
> > How it works
> > ============
> > 
> > Upon depletion of the hugetlb pool, rather than reporting an error immediately,
> > first try and allocate the needed huge pages directly from the buddy allocator.
> > Care must be taken to avoid unbounded growth of the hugetlb pool, so the
> > hugetlb filesystem quota is used to limit overall pool size.
> > 
> 
> If I understand hugetlb correctly, there is no accounting of hugepages
> to the RSS of any process. Since the pool will no longer be static,
> should we also consider changes to the accounting of hugepages?

You're right: there is no accounting of huge pages against a process.
This is also the case for the statically allocated pool so this
particular issue exists unconditionally.  There are several things
missing: RSS accounting, counting huge pages towards locked_vm limits,
etc...  The plan is to address these separately and to fix them all at
once.

In the absence of traditional per-process huge page accounting, the
kernel has provided an alternate means for restricting a process' access
to the global hugetlb pool: filesystem permissions and quotas.  It's not
ideal, but with this patch series, the filesystem permissions and quotas
remain the effective mechanism for restricting pool growth and
consumption by processes.

-- 
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center

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