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| author | Bruce Momjian <bruce@momjian.us> | 2004-11-09 03:57:42 +0000 |
|---|---|---|
| committer | Bruce Momjian <bruce@momjian.us> | 2004-11-09 03:57:42 +0000 |
| commit | 8dd602e41ee2c61fd62dc2a07270966be37bef28 (patch) | |
| tree | 8d6b16bf3ac86775d2281b5149a92f4addbcc995 | |
| parent | d9ab482abbb18cca6b6cb32dc46700431b208cb6 (diff) | |
| download | postgresql-8dd602e41ee2c61fd62dc2a07270966be37bef28.tar.gz postgresql-8dd602e41ee2c61fd62dc2a07270966be37bef28.zip | |
Update mmap details:
< portability issues. Anonymous mmap is required to prevent I/O
< overhead.
> portability issues. Anonymous mmap (or mmap to /dev/zero) is required
> to prevent I/O overhead.
>
> * Consider mmap()'ing files into a backend?
>
> Doing I/O to large tables would consume a lot of address space or
> require frequent mapping/unmapping. Extending the file also causes
> mapping problems that might require mapping only individual pages,
> leading to thousands of mappings. Another problem is that there is no
> way to _prevent_ I/O to disk from the dirty shared buffers so changes
> could hit disk before WAL is written.
| -rw-r--r-- | doc/TODO | 15 |
1 files changed, 12 insertions, 3 deletions
@@ -6,7 +6,7 @@ TODO list for PostgreSQL Bracketed items "[]" have more detail. Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) -Last updated: Mon Nov 8 15:16:11 EST 2004 +Last updated: Mon Nov 8 22:57:34 EST 2004 The most recent version of this document can be viewed at the PostgreSQL web site, http://www.PostgreSQL.org. @@ -815,8 +815,17 @@ Miscellaneous * Use mmap() rather than SYSV shared memory or to write WAL files (?) [mmap] This would remove the requirement for SYSV SHM but would introduce - portability issues. Anonymous mmap is required to prevent I/O - overhead. + portability issues. Anonymous mmap (or mmap to /dev/zero) is required + to prevent I/O overhead. + +* Consider mmap()'ing files into a backend? + + Doing I/O to large tables would consume a lot of address space or + require frequent mapping/unmapping. Extending the file also causes + mapping problems that might require mapping only individual pages, + leading to thousands of mappings. Another problem is that there is no + way to _prevent_ I/O to disk from the dirty shared buffers so changes + could hit disk before WAL is written. * Add a script to ask system configuration questions and tune postgresql.conf * Use a phantom command counter for nested subtransactions to reduce |