Re: [Patch] Optimize dropping of relation buffers using dlist

On Tue, Nov 5, 2019 at 10:34 AM Tomas Vondra
<tomas.vondra@2ndquadrant.com> wrote:
> 2) This adds another hashtable maintenance to BufferAlloc etc. but
>     you've only done tests / benchmark for the case this optimizes. I
>     think we need to see a benchmark for workload that allocates and
>     invalidates lot of buffers. A pgbench with a workload that fits into
>     RAM but not into shared buffers would be interesting.

Yeah, it seems pretty hard to believe that this won't be bad for some
workloads. Not only do you have the overhead of the hash table
operations, but you also have locking overhead around that. A whole
new set of LWLocks where you have to take and release one of them
every time you allocate or invalidate a buffer seems likely to cause a
pretty substantial contention problem.

-- 
Robert Haas
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