... > >> Without knowing what the device adapter is, hard to say where the problem is. I > >> suspect that with the patch applied, we may be ending up with a small default > >> max_sectors value, causing overhead due to more commands than necessary. > >> > >> Will check what I see with my test rig. > > > > As far as I can see, this patch should not make a difference unless the > > ATA shost driver is setting the max_sectors value unnecessarily low. > > That is my hunch too, hence my question about which host driver is being used > for this test... That is not apparent from the problem report. No one's fallen over the old problem and managed to limit the number of sectors in a read to the number of sectors in (IIRC) a 'multi sector' read that uses a single DMA burst? Was always a good way of killing disk performance. IIRC the maximum number of sectors for an ATA disk transfer is 255. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
