Re: [PATCH] speed up SATA

Nick Piggin
2004-03-27T23:37:56Z

Jeff Garzik wrote:
>
> The "lba48" feature in ATA allows for addressing of sectors > 137GB, and
> also allows for transfers of up to 64K sector, instead of the
> traditional 256 sectors in older ATA.
>
> libata simply limited all transfers to a 200 sectors (just under the 256
> sector limit). This was mainly being careful, and making sure I had a
> solution that worked everywhere. I also wanted to see how the iommu S/G
> stuff would shake out.
>
> Things seem to be looking pretty good, so it's now time to turn on
> lba48-sized transfers. Most SATA disks will be lba48 anyway, even the
> ones smaller than 137GB, for this and other reasons.
>
> With this simple patch, the max request size goes from 128K to 32MB...
> so you can imagine this will definitely help performance. Throughput
> goes up. Interrupts go down. Fun for the whole family.
>

Hi Jeff,
I think 32MB is too much. You incur latency and lose
scheduling grainularity. I bet returns start diminishing
pretty quickly after 1MB or so.