workqueue: reimplement WQ_HIGHPRI using a separate worker_pool
WQ_HIGHPRI was implemented by queueing highpri work items at the head
of the global worklist. Other than queueing at the head, they weren't
handled differently; unfortunately, this could lead to execution
latency of a few seconds on heavily loaded systems.
Now that workqueue code has been updated to deal with multiple
worker_pools per global_cwq, this patch reimplements WQ_HIGHPRI using
a separate worker_pool. NR_WORKER_POOLS is bumped to two and
gcwq->pools[0] is used for normal pri work items and ->pools[1] for
highpri. Highpri workers get -20 nice level and has 'H' suffix in
their names. Note that this change increases the number of kworkers
per cpu.
POOL_HIGHPRI_PENDING, pool_determine_ins_pos() and highpri chain
wakeup code in process_one_work() are no longer used and removed.
This allows proper prioritization of highpri work items and removes
high execution latency of highpri work items.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Josh Hunt <joshhunt00@gmail.com>
LKML-Reference: <CAKA=qzaHqwZ8eqpLNFjxnO2fX-tgAOjmpvxgBFjv6dJeQaOW1w@mail.gmail.com>
2 files changed
