On 18/11/22 19:27, Bart Van Assche wrote: > On 11/18/22 02:47, Adrian Hunter wrote: >> On 26/10/22 10:30, Christian Löhle wrote: >>> Mmcblk relies on block layer requeueing to fulfill some requests under >>> certain conditions. Improve the handling to get nicely ordered requests. >>> >>> Using the terms a bit loosely to get a point across: >>> Current behavior for 512 blksz and max_blk_count = 1 the scenario would >>> be as follows: >>> >>> - request for page 0 lba 0 to 7 >>> - request for page 1 lba 8 to 15 >>> - request for page 2 lba 16 to 23 >>> - request for page 3 lba 24 to 31 >>> >>> mmcblk modifies data->blocks = 1 for each and requeues, >>> this leads to: >>> >>> Access lba 0 >>> Access lba 8 >>> Access lba 16 >>> Access lba 24 >>> Access lba 1 (1. Requeue for page 0) >>> Access lba 9 (1. Requeue for page 1) >>> Access lba 17 (1. Requeue for page 2) >>> Access lba 25 (1. Requeue for page 3) >>> Access lba 2 (2. Requeue for page 0) >>> ... >>> >>> Of course we would rather have lbas consecutive. >> >> Does anyone know why the block layer does not support >> (max_hw_sectors << 9) < PAGE_SIZE ? > > Hi Adrian, > > Does this mean that the following patch series would not only be > useful for UFS but also for MMC? "[PATCH 00/10] Support DMA segments > smaller than the page size" > (https://lore.kernel.org/linux-block/20221019222324.362705-1-bvanassche@xxxxxxx/). That patchset still does not allow max_hw_sectors = 1 which is what Christian's case needs.
