"David Boreham" <david_list@boreham.org> 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