Hello, We are allowed to build all scheduler as modules or build-in setting defaults with CONFIG_SCSI_MQ_DEFAULT=y/n / CONFIG_DM_MQ_DEFAULT=y/n. Following setup: All scheduler set to Y ( build-in ) CONFIG_DEFAULT_CFQ=y CONFIG_SCSI_MQ_DEFAULT and CONFIG_DM_MQ_DEFAULT set to N Boot now with elevator=some_mq_schedule While it should not even try to use any MQ it will try to set values from elevator and hang. Now boot with scsi_mod.use_blk_mq=y dm_mod.use_blk_mq=y elevator=!some_mq_schedule , hangs too. This looks better but still some output in dmesg is wrong: Build scheduler M ( I have cfq mq-deadline Y to have some defaults) CONFIG_DEFAULT_CFQ=y CONFIG_SCSI_MQ_DEFAULT and CONFIG_DM_MQ_DEFAULT set to N Boot with elevator=some_mq_schedule_is_module Will give an error since it can't find the module and continue with default cfq which is fine. Once box is up modprobe the modules you used in elevator= and whatch your dmesg.. So how is that meant to work now ? use elevator= only you know what your kernel config looks like ( which probably lots users have no clue about ) ? Best Regards, Gabriel C
