On 01 Feb 2006 03:59:16 -0500, Jes Sorensen <jes@xxxxxxx> wrote:This one takes care of a problem with the SGI IOC4 driver where it
hits DMA problems if the request grows too large.
Does this happen only for CONFIG_IA64_PAGE_SIZE_4KB=y
or CONFIG_IA64_PAGE_SIZE_8KB=y?
from sgiioc4.c:
/* Each Physical Region Descriptor Entry size is 16 bytes (2 * 64 bits) */
/* IOC4 has only 1 IDE channel */
#define IOC4_PRD_BYTES 16
#define IOC4_PRD_ENTRIES (PAGE_SIZE /(4*IOC4_PRD_BYTES))
As limiting request size to 127 sectors punishes performance
wouldn't it be better to define IOC4_PRD_ENTRIES to 256
if this is possible (would need 4 pages for PAGE_SIZE=4096
and 2 for PAGE_SIZE=8192)?