----- Mensagem original ----- | Andrà Volpato wrote: | > | | > | If it is being spent in the bitmap index scan, try setting | > | effective_io_concurrency to 0 for Linux, and see what effect that | > | has. | > | > I disabled effective_io_concurrency at AIX but it made no changes on | > bitmap index times. | > | | Brad's point is that it probably doesn't do anything at all on AIX, | and | is already disabled accordingly. But on Linux, it is doing something, | and that might be contributing to why it's executing so much better on | that platform. If you disable that parameter on your Debian box, that | should give you an idea whether that particular speed-up is a major | component to the difference you're seeing or not. HereÂs new explains based on Debian box: (1) effective_io_concurrency = 5 # /etc/init.d/postgresql stop # echo 3 > /proc/sys/vm/drop_caches # /etc/init.d/postgresql start http://explain.depesz.com/s/br (2) effective_io_concurrency = 0 # /etc/init.d/postgresql stop # echo 3 > /proc/sys/vm/drop_caches # /etc/init.d/postgresql start http://explain.depesz.com/s/3A0 BitmapAnd really gets improved a little bit in (1), but Bitmap index scans got a lot worse. | -- | Greg Smith 2ndQuadrant US greg@xxxxxxxxxxxxxxx Baltimore, MD | PostgreSQL Training, Services and Support www.2ndQuadrant.us | "PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books []Âs, Andre Volpato -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
