Re: [RFC 0/8] Cpuset aware writeback

[Andi Kleen]

> Secondly we modify the dirty limit calculation to be based
> on the acctive cpuset.

The global dirty limit definitely seems to be a problem
in several cases, but my feeling is that the cpuset is the wrong unit
to keep track of it. Most likely it should be more fine grained.

> If we are in a cpuset then we select only inodes for writeback
> that have pages on the nodes of the cpuset.

Is there any indication this change helps on smaller systems
or is it purely a large system optimization?

> B. We add a new counter NR_UNRECLAIMABLE that is subtracted
>    from the available pages in a node. This allows us to
>    accurately calculate the dirty ratio even if large portions
>    of the node have been allocated for huge pages or for
>    slab pages.

That sounds like a useful change by itself.

-Andi
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