Messages in this thread | | | Date | Sat, 19 Dec 1998 09:51:01 +1300 | From | Chris Wedgwood <> | Subject | Re: mmap() is slower than read() on SCSI/IDE on 2.0 and 2.1 |
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On Fri, Dec 18, 1998 at 09:05:26PM +0100, Rik van Riel wrote:
> Some form of read-behind will give us optimal performance > when the tiles are a lot smaller (say 1/4th) than the VM > 'stripe size' we are using.
Still wearning my "I'm not sure its always a good idea to second guess the application hat" -- do we actually have any applications that would make use of this?
The only one I can think of is that I have large databases (well, 1 GB or so) that have sequentially grown and at time, we do queries that requires us walking backwards though the data here, but I don't think it uses mmap.
I know other `theorietical applications' exist that produce this pattern, but then I can find `theorietical applications' that have any kind of screwy access pattern.
> The actual disk I/O, of course, is still done in forward > direction :)
True... but if this is an issue, gobs of disk and RAID can help, especially when it comes to random seeks.
-cw
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