Messages in this thread |  | | Date | Wed, 13 Sep 2000 05:39:14 -0700 | From | Mitchell Blank Jr <> | Subject | Re: (reiserfs) Re: More on 2.2.18pre2aa2 |
| |
Alan Cox wrote: > > Yes, but "how hard is it reasonable for the kernel to try" is based on > > both items. A good first order approximation is number of requests. > > I must strongly disagree with that claim. A request could be 512 bytes or > 128K.
Yeah, as sct pointed out this gets thorny. For a modern harddrive this probably doesn't matter (since sequential I/O is SO fast compared to seek times) but for other devices its an issue.
> > ...where the user sets a number exlpicitly for what performance they > > want. Again, if we're going to make the user set this latency > > No they do not. The parameters are defined by the bandwidth and measured > behaviour.
Hmmm... well if someone wants to propose an algorithm to self-tune the "queue depth in milliseconds" number then maybe we'll get somewhere. You'd need to do some sort of moving averages of both requests/sec and sectors/sec that come out of the elevator and use those as feedback to adjust the queue-depth-value. I'm not sure if this is advisable, but at least it sounds feasable.
-Mitch - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
|  |