pgsql: Update mmap details: < portability issues.
Log Message:
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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.
Modified Files:
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pgsql/doc:
TODO (r1.1390 -> r1.1391)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1390&r2=1.1391)