From: Keith Busch <kbusch@xxxxxxxxxx> Previous version is here: https://lore.kernel.org/linux-nvme/20250805195608.2379107-1-kbusch@xxxxxxxx/ This patch set depends on this unmerged series for flexible direct-io here: https://lore.kernel.org/linux-block/20250819164922.640964-1-kbusch@xxxxxxxx/ The purpose of this is to allow optimization decisions to happen per IO. The virtual boundary that NVMe reports provides specific guarantees about the data alignment, but that might not be large enough for some CPU architectures to take advantage of even iif an applications uses aligned data buffers that could use it. At the same time, the virtual boundary prevents the driver from directly using memory in ways the hardware may be capable of accessing. This creates unnecessary needs on applications to double buffer their data into the more restrictive virtually contiguous format. This patch series provides an efficient way to track page boundary gaps per-IO so that the optimizations can be decided per-IO. This provides flexibility to use all hardware to their abilities beyond what the virtual boundary mask can provide. Note, abuse of this capability may result in worse performance compared to the bounce buffer solutions. Sending a bunch of tiny vectors for one IO incurs significant protocol overhead, so while this patch set allows you to do that, I recommend that you don't. We can't enforce a minimum size though because vectors may straddle pages with only a few words in the first and/or last pages, which we do need to support. Changes from v2: - We only need to know about the lowest set bit in any bio vector page gap. Use that to avoid increasing the bio size - Fixed back merges; the previous was potentially missing one of the bio's gaps - Use pointers instead of relying on the inline to generate good code. - Trivial name changes - Comments explaing the new bio field, and the nvme usage for deciding on SGL vs PRP DMA. Keith Busch (2): block: accumulate segment page gaps per bio nvme: remove virtual boundary for sgl capable devices block/bio.c | 1 + block/blk-merge.c | 39 ++++++++++++++++++++++++++++++++++++--- block/blk-mq-dma.c | 3 +-- block/blk-mq.c | 10 ++++++++++ drivers/nvme/host/core.c | 21 ++++++++++++++++----- drivers/nvme/host/pci.c | 16 +++++++++++++--- include/linux/blk-mq.h | 2 ++ include/linux/blk_types.h | 8 ++++++++ 8 files changed, 87 insertions(+), 13 deletions(-) -- 2.47.3
