Messages in this thread | | | Subject | Re: [PATCH] Configure IDE probe delays | From | Lee Revell <> | Date | Wed, 01 Sep 2004 15:08:39 -0400 |
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On Wed, 2004-09-01 at 11:06, Alan Cox wrote: > On Mer, 2004-09-01 at 14:20, Mark Lord wrote: > > LBA48 is only needed when (1) the sector count is greater than 256, > > and/or (2) the ending sector number >= (1<<28). > > I've played with this a bit and in the -ac IDE code it can drop back > to LBA28 for devices that are small enough not to need LBA48 when the > controller only supports PIO for LBA48 modes (eg some ALi) as 2.4-ac > did. > > > I regularly include this optimisation in the drivers I have been > > working on since LBA48 first appeared. > > It isn't always a win. You get cut down to 256 sectors per I/O which for > some workloads has a cost and you need to factor that into the command > issue choice as well as the last sector number being accessed. >
I have never been able to measure a decrease in disk throughput in any disk benchmark with 256 sectors per I/O vs. 1024. This is a modestly powered desktop with a single drive though. What kinds of workloads would you expect to be affected by this?
Lee
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