Re: Wait free LW_SHARED acquisition

Hi,

Over at -performance Mark Kirkwood tested a recent version of this
(http://archives.postgresql.org/message-id/53B283F3.7020005%40catalyst.net.nz)
. I thought it's interesting to add the numbers to this thread:

> Test: pgbench
> Options: scale 500
> read only
> Os: Ubuntu 14.04
> Pg: 9.3.4
> Pg Options:
> max_connections = 200
> shared_buffers = 10GB
> maintenance_work_mem = 1GB
> effective_io_concurrency = 10
> wal_buffers = 32MB
> checkpoint_segments = 192
> checkpoint_completion_target = 0.8
>
>
> Results
>
> Clients | 9.3 tps 32 cores | 9.3 tps 60 cores
> --------+------------------+-----------------
> 6 | 70400 | 71028
> 12 | 98918 | 129140
> 24 | 230345 | 240631
> 48 | 324042 | 409510
> 96 | 346929 | 120464
> 192 | 312621 | 92663
>
> So we have anti scaling with 60 cores as we increase the client connections.
> Ouch! A level of urgency led to trying out Andres's 'rwlock' 9.4 branch [1]
> - cherry picking the last 5 commits into 9.4 branch and building a package
> from that and retesting:
>
> Clients | 9.4 tps 60 cores (rwlock)
> --------+--------------------------
> 6 | 70189
> 12 | 128894
> 24 | 233542
> 48 | 422754
> 96 | 590796
> 192 | 630672

Now, this is a bit of a skewed comparison due to 9.4 vs. 9.3 but still
interesting.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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