Re: [RFC PATCH V5] mm readahead: Fix readahead fail for no localmemory and limit readahead pages

From: David Rientjes
Date: Fri Feb 07 2014 - 15:41:48 EST


On Fri, 7 Feb 2014, Raghavendra K T wrote:

> So following discussion TODO for my patch is:
>
> 1) Update the changelog with user visible impact of the patch.
> (Andrew's suggestion)
> 2) Add ACCESS_ONCE to numa_node_id().
> 3) Change the "readahead into remote memory" part of the documentation
> which is misleading.
>
> ( I feel no need to add numa_mem_id() since we would specifically limit
> the readahead with MAX_REMOTE_READAHEAD in memoryless cpu cases).
>

I don't understand what you're saying, numa_mem_id() is local memory to
current's cpu. When a node consists only of cpus and not memory it is not
true that all memory is then considered remote, you won't find that in any
specification that defines memory affinity including the ACPI spec. I can
trivially define all cpus on my system to be on memoryless nodes and
having that affect readahead behavior when, in fact, there is affinity
would be ridiculous.
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