On Wed, Jan 24, 2024 at 07:59:54PM +0800, Ming Lei wrote: > Hello, > > Requests are added to plug list in reverse order, and both virtio-blk > and nvme retrieves request from plug list in order, so finally requests > are submitted to hardware in reverse order via nvme_queue_rqs() or > virtio_queue_rqs, see: > May this reorder be one problem for virtio-blk and nvme-pci? It it isn't really a problem for the drivers, but de-serializing I/O patterns tends to be not good. I know at least a couple cases where this would hurt: - SSDs with sequential write detection - zoned SSDs with zoned append, as this now turns a sequential user write pattern into one that is fairly random - HDDs much prefer real sequential I/O, although until nvme HDDs go beyong the prototype stage that's probably not hitting this case yet So yes, we should fix this. > > > Thanks, > Ming > > ---end quoted text---
