Messages in this thread | | | Date | Sun, 6 Apr 2003 15:32:50 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] take 48-bit lba a bit further |
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On Sun, Apr 06 2003, John Bradford wrote: > > Thanks for taking the previous bit Alan, here's an incremental update to > > 2.5.66-ac2. Just cleans up the 'when to use 48-bit lba' logic a bit per > > Andries suggestion, and also expands the request size for 48-bit lba > > capable drives to 512KiB. > > > > Works perfectly in testing here, ext2/3 generates nice big 512KiB > > requests and the drive flies. > > Then, don't we want to be using 48-bit lba all the time on compatible devices > instead of falling back to 28-bit when possible to save a small amount of > instruction overhead? (Or is that what we're doing already? I haven't really > had the time to follow this thread).
The logic in the patch is to enable large requests _if_ the drive can do 48-bit lba. However, we will only use 48-bit lba commands if the request is either beyond 2^28 sectors _or_ bigger than 256 sectors since neither of these can be addressed with 28-bit lba.
See rq_lba48 in the patch, it explains it.
-- Jens Axboe
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