pgsql: snapshot scalability: Move PGXACT->vacuumFlags to ProcGlobal->va

snapshot scalability: Move PGXACT->vacuumFlags to ProcGlobal->vacuumFlags.

Similar to the previous commit this increases the chance that data
frequently needed by GetSnapshotData() stays in l2 cache. As we now
take care to not unnecessarily write to ProcGlobal->vacuumFlags, there
should be very few modifications to the ProcGlobal->vacuumFlags array.

Author: Andres Freund <andres(at)anarazel(dot)de>
Reviewed-By: Robert Haas <robertmhaas(at)gmail(dot)com>
Reviewed-By: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Reviewed-By: David Rowley <dgrowleyml(at)gmail(dot)com>
Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5788e258bb26495fab65ff3aa486268d1c50b123

Modified Files
--------------
src/backend/access/transam/twophase.c | 2 +-
src/backend/commands/vacuum.c | 5 ++-
src/backend/postmaster/autovacuum.c | 6 +--
src/backend/replication/logical/logical.c | 3 +-
src/backend/replication/slot.c | 3 +-
src/backend/storage/ipc/procarray.c | 66 ++++++++++++++++++++-----------
src/backend/storage/lmgr/deadlock.c | 4 +-
src/backend/storage/lmgr/proc.c | 16 +++++---
src/include/storage/proc.h | 12 +++++-
9 files changed, 75 insertions(+), 42 deletions(-)