On Tue, Nov 27, 2012 at 4:09 AM, Jens Axboe <[email protected]> wrote: > On 2012-11-27 01:35, Laine Walker-Avina wrote: >> Hi all, >> >> We are experiencing an issue with doing direct IO to a NVMe device I'm >> helping to develop. Every so often, the physical address given by >> sg_dma_address() is aligned to 0x800 instead of 0x1000 as specified by >> blk_queue_dma_alignement(queue, 4095) when the queue is initialized. >> The request is also split over multiple segments to make up for the >> missing space (eg: for a 4k IO it's split into two segments 2k in >> size, and for an 8k IO it's split into 3 segments--2k,4k,2k). Our >> design requires the physical segments given to the device be aligned >> to 4k boundaries and be multiples of 4k in size. When not doing direct >> IO the physical addresses appear to always be 4k aligned as expected. >> One possible issue is the kernel we're primarily testing against is >> 2.6.32-220 from CentOS, but we have observed similar behavior from a >> vanilla 3.3 kernel as well. Any help would be greatly appreciated. > > I'm assuming you set the hardware sector size to 4k as well? > > -- > Jens Axboe >
Yes, as well as the logical block size and io_min. Laine Walker-Avina -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
