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Re: [PATCH v5 3/9] mm/swap: Split swap cache into 64MB trunks

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> Switching from a single radix-tree to an array of radix-trees to reduce
> contention seems a bit hacky.  That we can do this and have everything
> continue to work tells me that we're simply using an inappropriate data
> structure to hold this info.

What would you use instead?

A tree with fine grained locking?

FWIW too fine grained locking (e.g. on every node) is usually a bad idea: 

it slows down the single thread performance and it causes much more overhead
when there is actual contention because too much time is spent bouncing cache
lines around.

So I actually like the "a little bit more fine grained, but not too much"
approach.

Or a hash table? 

Not sure if this would work here.

-Andi

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[PATCH v5 3/9] mm/swap: Split swap cache into 64MB trunks Tim Chen <tim.c.chen@linux.intel.com> - 2017-01-11 19:00 +0100
  Re: [PATCH v5 3/9] mm/swap: Split swap cache into 64MB trunks Andrew Morton <akpm@linux-foundation.org> - 2017-01-12 00:10 +0100
    Re: [PATCH v5 3/9] mm/swap: Split swap cache into 64MB trunks Andi Kleen <ak@linux.intel.com> - 2017-01-12 00:20 +0100
      Re: [PATCH v5 3/9] mm/swap: Split swap cache into 64MB trunks Tim Chen <tim.c.chen@linux.intel.com> - 2017-01-12 17:50 +0100

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