On Mon, 20 Jan 2003 18:10:24 +0100 (CET), "Moritz Lennert" <[EMAIL PROTECTED]> wrote: >I'll try that, although I haven't changed any of the tuples since import >of the data (this is a static table...)
Then I must have miscalculated something :-( What does VACUUM VERBOSE ANALYZE <yourtable> say? >> From what I've seen I think that the planner is right to choose a seq >> scan. 226 seconds for reading 120K pages (~ 1GB) is not very >> impressive, though. What kind of disk do you have? > >IDE, Samsung, 7200rpm > >> Is your disk heavily fragmented? > >It shouldn't be. > >> Did you enable DMA? > >No, should I ? Yes. Here is what I got on a P IV 2 GHz with a Seagate 7200rpm(?) disk: ~ # hdparm -t -T /dev/hda /dev/hda: Timing buffer-cache reads: 128 MB in 0.39 seconds =328.21 MB/sec Timing buffered disk reads: 64 MB in 2.49 seconds = 25.70 MB/sec vs. ~ # hdparm -t -T /dev/hda /dev/hda: Timing buffer-cache reads: 128 MB in 0.37 seconds =345.95 MB/sec Timing buffered disk reads: 64 MB in 23.38 seconds = 2.74 MB/sec ~ # l xx -rw-r--r-- 1 root root 1332104434 2003-01-20 19:04 xx ~ # time dd if=xx of=/dev/null bs=8k 162610+1 Records in 162610+1 Records out real 0m48.665s user 0m0.150s sys 0m1.690s ~ # hdparm -d 0 /dev/hda ~ # time dd if=xx of=/dev/null bs=8k 162610+1 Records in 162610+1 Records out real 7m42.666s user 0m0.270s sys 1m27.160s With DMA: More than 3000 pages / second Without DMA: ~ 350 pages / second Your throughput: ~ 530 pages / second >> recommend setting shared_buffers to something in the range [1000, >> 4000]. >> And one of my favorites: effective_cache_size = 40000 > >I will have to increase /proc/sys/kernel/shmmax for that, or ? Maybe for shared_buffers. Certainly not for effective_cache_size. The latter does not consume resources, it's just a hint for the planner. Servus Manfred ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
