On 2022/09/27 7:01, Khazhismel Kumykov wrote: > Setting IO scheduler at device init time in kernel is useful, and moving > this option into kernel config makes it possible to build different > kernels with different default schedulers from the same tree. > > Order deadline->none->rest to retain current behavior of using "none" by > default if mq-deadline is not enabled. > > Signed-off-by: Khazhismel Kumykov <khazhy@xxxxxxxxxx> > --- > checkpatch suggested more verbose help descriptions, but I felt it'd be > too much repeated from the main config options, so opted to leave them > out. > > block/Kconfig.iosched | 28 ++++++++++++++++++++++++++++ > block/elevator.c | 2 +- > 2 files changed, 29 insertions(+), 1 deletion(-) > > diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched > index 615516146086..38a83282802a 100644 > --- a/block/Kconfig.iosched > +++ b/block/Kconfig.iosched > @@ -43,4 +43,32 @@ config BFQ_CGROUP_DEBUG > Enable some debugging help. Currently it exports additional stat > files in a cgroup which can be useful for debugging. > > +choice > + prompt "Default I/O scheduler" > + default DEFAULT_MQ_DEADLINE > + help > + Select the I/O scheduler which will be used by default for block devices > + with a single hardware queue. > + > +config DEFAULT_MQ_DEADLINE > + bool "MQ Deadline" if MQ_IOSCHED_DEADLINE=y > + > +config DEFAULT_NONE > + bool "none" > + > +config DEFAULT_MQ_KYBER > + bool "Kyber" if MQ_IOSCHED_KYBER=y > + > +config DEFAULT_BFQ > + bool "BFQ" if IOSCHED_BFQ=y > + > +endchoice > + > +config MQ_DEFAULT_IOSCHED > + string > + default "mq-deadline" if DEFAULT_MQ_DEADLINE > + default "none" if DEFAULT_NONE > + default "kyber" if DEFAULT_MQ_KYBER > + default "bfq" if DEFAULT_BFQ > + > endmenu > diff --git a/block/elevator.c b/block/elevator.c > index c319765892bb..4137933dfd16 100644 > --- a/block/elevator.c > +++ b/block/elevator.c > @@ -642,7 +642,7 @@ static struct elevator_type *elevator_get_default(struct request_queue *q) > !blk_mq_is_shared_tags(q->tag_set->flags)) > return NULL; > > - return elevator_get(q, "mq-deadline", false); > + return elevator_get(q, CONFIG_MQ_DEFAULT_IOSCHED, false); This will allow a configuration to specify bfq or kyber for all single queue devices, which include SMR HDDs. Since these can only use mq-deadline (or none if the user like living dangerously), this default config-based solution is not OK in my opinion. What is wrong with using a udev rule to set the default disk scheduler ? Most distros do that already anyway, so this config may not even be that useful in practice. What is the use case here ? > } > > /* -- Damien Le Moal Western Digital Research
