How to send 1MB I/O size in a single I/O request without split

[Scott Long]

> On Jan 30, 2015, at 3:18 AM, Sibananda Sahu <sibananda.sahu at avagotech.com> wrote:
> 
> Hi Scott,
> 
> One more thing to ask.
> 
> I think even if I will modify the bus_dma_tag in our driver to have a max
> segment of 4K, the max I/O length per I/O request that will come is 128KB
> because of the MAXPHYS limitation.
> I have tested this by restricting the MAXPHYS to 128KB again and when I
> requested an I/O with bs=1M the I/O was split with various length I/O
> requests.
> 
> Does this implies that tuning the MAXPHYS is the ultimate solution to get
> larger I/O size??

Yes.  You will need to rebuild your kernel with the larger size.  Some day we might default to a larger size, or make it dynamic.

Scott