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cfq: don't use icq_get_changed()

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cfq caches the associated cfqq's for a given cic.  The cache needs to
be flushed if the cic's ioprio or blkcg has changed.  It is currently
done by requiring the changing action to set the respective
ICQ_*_CHANGED bit in the icq and testing it from cfq_set_request(),
which involves iterating through all the affected icqs.

All cfq wants to know is whether ioprio and/or blkcg have changed
since the last flush and can be easily achieved by just remembering
the current ioprio and blkcg ID in cic.

This patch adds cic->{ioprio|blkcg_id}, updates all ioprio users to
use the remembered value instead, and updates cfq_set_request() path
such that, instead of using icq_get_changed(), the current values are
compared against the remembered ones and trigger appropriate flush
action if not.  Condition tests are moved inside both _changed
functions which are now named check_ioprio_changed() and
check_blkcg_changed().

ioprio.h::task_ioprio*() can't be used anymore and replaced with
open-coded IOPRIO_CLASS_NONE case in cfq_async_queue_prio().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo 2012-03-19 15:10:58 -07:00 • committed by Jens Axboe
parent abede6da27
commit 598971bfbd
2 changed files with 45 additions and 40 deletions
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22
include/linux/ioprio.h
View file

@ -41,27 +41,15 @@ enum {
IOPRIO_WHO_USER,
};
/*
* Fallback BE priority
*/
#define IOPRIO_NORM (4)
/*
* if process has set io priority explicitly, use that. if not, convert
* the cpu scheduler nice value to an io priority
*/
#define IOPRIO_NORM (4)
static inline int task_ioprio(struct io_context *ioc)
{
if (ioprio_valid(ioc->ioprio))
return IOPRIO_PRIO_DATA(ioc->ioprio);
return IOPRIO_NORM;
}
static inline int task_ioprio_class(struct io_context *ioc)
{
if (ioprio_valid(ioc->ioprio))
return IOPRIO_PRIO_CLASS(ioc->ioprio);
return IOPRIO_CLASS_BE;
}
static inline int task_nice_ioprio(struct task_struct *task)
{
return (task_nice(task) + 20) / 5;