"David Boreham" <[EMAIL PROTECTED]> wrote > > BTW, I heard a long time ago that NTFS has quite fancy read-ahead, where > it attempts to detect the application's access pattern including if it is > reading sequentially and even if there is a 'stride' to the accesses when > they're not contiguous. I would imagine that other filesystems attempt > similar tricks. So one might expect a simple linear prefectch > to not help much in the presence of such a filesystem. >
So we need more tests. I understand how smart current file systems are, and seems that depends on the interval that you send next file block read request (decided by cpu_cost parameter in my program). I imagine on a multi-way machine with strong IO device, the ice-breaker could do much better ... > Were you worried about the icebreaker thread getting too far ahead of the > scan ? If it did it might page out the data you're about to read, I think. > Of course this could be fixed by having the read ahead thread perodically > check the current location being read by the query thread and pausing if > it's got too far ahead. > Right. Regards, Qingqing ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
