On 7/7/23 10:50, Bart Van Assche wrote: > On 7/6/23 17:38, Ming Lei wrote: >> Given blk_mq_sched_try_insert_merge is only called from bfq and >> deadline, it may not matter to apply this optimization. > > Without this patch, the documentation of the "nomerges" sysfs > attribute is incorrect. I need this patch because I want the > ability to disable merging even if an I/O scheduler has been > selected. As mentioned in the patch description, I discovered > this while I was writing a shell script that submits various > I/O workloads to a block device. Ming's point still stands I think: blk_queue_nomerges(q) is the first thing checked in elv_attempt_insert_merge(). So your patch should be a no-op and disabling merging through sysfs should still be effective. Why is your patch changing anything ? Moving blk_mq_sched_try_insert_merge() call to rq_mergeable(rq) inside elv_attempt_insert_merge() would also make a lot of sense I think. With that, blk_mq_sched_try_insert_merge() would be reduced to calling only elv_attempt_insert_merge(), which means that elv_attempt_insert_merge() could go away. -- Damien Le Moal Western Digital Research
