Messages in this thread | | | From | David Laight <> | Subject | RE: [ata] 0568e61225: stress-ng.copy-file.ops_per_sec -15.0% regression | Date | Tue, 9 Aug 2022 15:16:26 +0000 |
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... > >> 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
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