So what's the best course of action for increasing the 512kb IO transfer size limit, changing SCSI_MAX_PHYS_SEGMENTS (currently 128 and apparently can be set no greater than 256), or increasing the page size? Or is there another option. thanks - jc James Bottomley wrote: > > On Wed, 2007-01-10 at 15:07 -0800, john clyne wrote: >> So given that the HBA max_sectors_kb looks sufficiently large, my >> interpretation of your article is the next place I need to look is at >> ajusting SCSI_MAX_PHYS_SEGMENTS. Sounds like i can only increase this to >> 256. Does that than give me a max transfer size of 256 * page_size (4k) = >> 1MB? Is 1MB the limit or am I missing something? > > Well ... that's not the maximum possible ... just the maximum number of > SG elements. If the buffer is completely fragmented in physical memory, > then it will be 1MB ... however, linux does a reasonable job of getting > physically contiguous pages into a large memory allocation, so you could > get transfers that are larger than the 1MB limit by quite a way. And, > of course, any system that has a larger page size or uses an iommu will > go over this 1MB as well. > > Jmaes > > > - > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- View this message in context: http://www.nabble.com/IO-transfer-limits-tf2953389.html#a8284792 Sent from the linux-scsi mailing list archive at Nabble.com. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
