pgsql: Increase the number of buffer mapping partitions to 128.

Increase the number of buffer mapping partitions to 128.

Testing by Amit Kapila, Andres Freund, and myself, with and without
other patches that also aim to improve scalability, seems to indicate
that this change is a significant win over the current value and over
smaller values such as 64. It's not clear how high we can push this
value before it starts to have negative side-effects elsewhere, but
going this far looks OK.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/3acc10c997f916f6a741d0b4876126b7b08e3892

Modified Files
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src/backend/storage/lmgr/lwlock.c | 8 ++++----
src/include/storage/lwlock.h | 2 +-
2 files changed, 5 insertions(+), 5 deletions(-)