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Andres Freund 7975c5e0a9 Allow the WAL writer to flush WAL at a reduced rate. ... Commit 4de82f7d7 increased the WAL flush rate, mainly to increase the likelihood that hint bits can be set quickly. More quickly set hint bits can reduce contention around the clog et al. But unfortunately the increased flush rate can have a significant negative performance impact, I have measured up to a factor of ~4. The reason for this slowdown is that if there are independent writes to the underlying devices, for example because shared buffers is a lot smaller than the hot data set, or because a checkpoint is ongoing, the fdatasync() calls force cache flushes to be emitted to the storage. This is achieved by flushing WAL only if the last flush was longer than wal_writer_delay ago, or if more than wal_writer_flush_after (new GUC) unflushed blocks are pending. Based on some tests the default for wal_writer_delay is 1MB, which seems to work well both on SSD and rotational media. To avoid negative performance impact due to 4de82f7d7 an earlier commit (db76b1e) made SetHintBits() more likely to succeed; preventing performance regressions in the pgbench tests I performed. Discussion: 20160118163908.GW10941@awork2.anarazel.de		10 years ago
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access	Allow the WAL writer to flush WAL at a reduced rate.	10 years ago
bootstrap	Fix typos in comments and doc	10 years ago
catalog	Refactor check_functional_grouping() to use get_primary_key_attnos().	10 years ago
commands	Make concurrent refresh check early that there is a unique index on matview.	10 years ago
executor	ExecHashRemoveNextSkewBucket must physically copy tuples to main hashtable.	10 years ago
foreign	Remove parallel-safety check from GetExistingLocalJoinPath.	10 years ago
lib	Add two HyperLogLog functions	10 years ago
libpq	Properly close token in sspi authentication	10 years ago
main	Update copyright for 2016	10 years ago
nodes	Introduce extensible node types.	10 years ago
optimizer	Remove GROUP BY columns that are functionally dependent on other columns.	10 years ago
parser	Move pg_constraint.h function declarations to new file pg_constraint_fn.h.	10 years ago
po	Translation updates	11 years ago
port	Windows: Make pg_ctl reliably detect service status	10 years ago
postmaster	Allow the WAL writer to flush WAL at a reduced rate.	10 years ago
regex	Suppress compiler warnings about useless comparison of unsigned to zero.	10 years ago
replication	Make builtin lwlock tranche names consistent.	10 years ago
rewrite	Update copyright for 2016	10 years ago
snowball	Update copyright for 2016	10 years ago
storage	Make GetLockStatusData's header comment resemble reality.	10 years ago
tcop	Update copyright for 2016	10 years ago
tsearch	Avoid use of sscanf() to parse ispell dictionary files.	10 years ago
utils	Allow the WAL writer to flush WAL at a reduced rate.	10 years ago
.gitignore	Add .gitignore entries for AIX-specific intermediate build artifacts.	11 years ago
Makefile	Add support for systemd service notifications	10 years ago
common.mk	Remove maintainer-check target, fold into normal build	12 years ago
nls.mk	Remove trailing slashes from directories in find command	10 years ago