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| author | Andres Freund <andres@anarazel.de> | 2020-08-13 16:25:21 -0700 |
|---|---|---|
| committer | Andres Freund <andres@anarazel.de> | 2020-08-13 16:25:21 -0700 |
| commit | 1f51c17c68d05c28d5b9294d8013cb9e7e653160 (patch) | |
| tree | bb2dc0ab3009ced3ccfe819aba406f1f5810d4e4 /src/backend/access/gist/gistxlog.c | |
| parent | a811ea5bde2fbf450095994b5726dcbf64d68668 (diff) | |
| download | postgresql-1f51c17c68d05c28d5b9294d8013cb9e7e653160.tar.gz postgresql-1f51c17c68d05c28d5b9294d8013cb9e7e653160.zip | |
snapshot scalability: Move PGXACT->xmin back to PGPROC.
Now that xmin isn't needed for GetSnapshotData() anymore, it leads to
unnecessary cacheline ping-pong to have it in PGXACT, as it is updated
considerably more frequently than the other PGXACT members.
After the changes in dc7420c2c92, this is a very straight-forward change.
For highly concurrent, snapshot acquisition heavy, workloads this change alone
can significantly increase scalability. E.g. plain pgbench on a smaller 2
socket machine gains 1.07x for read-only pgbench, 1.22x for read-only pgbench
when submitting queries in batches of 100, and 2.85x for batches of 100
'SELECT';. The latter numbers are obviously not to be expected in the
real-world, but micro-benchmark the snapshot computation
scalability (previously spending ~80% of the time in GetSnapshotData()).
Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Robert Haas <robertmhaas@gmail.com>
Reviewed-By: Thomas Munro <thomas.munro@gmail.com>
Reviewed-By: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de
Diffstat (limited to 'src/backend/access/gist/gistxlog.c')
| -rw-r--r-- | src/backend/access/gist/gistxlog.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/src/backend/access/gist/gistxlog.c b/src/backend/access/gist/gistxlog.c index a63b05388c5..dcd28f678b3 100644 --- a/src/backend/access/gist/gistxlog.c +++ b/src/backend/access/gist/gistxlog.c @@ -389,7 +389,7 @@ gistRedoPageReuse(XLogReaderState *record) * * latestRemovedXid was the page's deleteXid. The * GlobalVisIsRemovableFullXid(deleteXid) test in gistPageRecyclable() - * conceptually mirrors the pgxact->xmin > limitXmin test in + * conceptually mirrors the PGPROC->xmin > limitXmin test in * GetConflictingVirtualXIDs(). Consequently, one XID value achieves the * same exclusion effect on primary and standby. */ |