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linux-next/include/linux/ioprio.h
Tejun Heo 598971bfbd cfq: don't use icq_get_changed()
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>
2012-03-20 12:47:47 +01:00

80 lines
2.0 KiB
C

#ifndef IOPRIO_H
#define IOPRIO_H
#include <linux/sched.h>
#include <linux/iocontext.h>
/*
* Gives us 8 prio classes with 13-bits of data for each class
*/
#define IOPRIO_BITS (16)
#define IOPRIO_CLASS_SHIFT (13)
#define IOPRIO_PRIO_MASK ((1UL << IOPRIO_CLASS_SHIFT) - 1)
#define IOPRIO_PRIO_CLASS(mask) ((mask) >> IOPRIO_CLASS_SHIFT)
#define IOPRIO_PRIO_DATA(mask) ((mask) & IOPRIO_PRIO_MASK)
#define IOPRIO_PRIO_VALUE(class, data) (((class) << IOPRIO_CLASS_SHIFT) | data)
#define ioprio_valid(mask) (IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
/*
* These are the io priority groups as implemented by CFQ. RT is the realtime
* class, it always gets premium service. BE is the best-effort scheduling
* class, the default for any process. IDLE is the idle scheduling class, it
* is only served when no one else is using the disk.
*/
enum {
IOPRIO_CLASS_NONE,
IOPRIO_CLASS_RT,
IOPRIO_CLASS_BE,
IOPRIO_CLASS_IDLE,
};
/*
* 8 best effort priority levels are supported
*/
#define IOPRIO_BE_NR (8)
enum {
IOPRIO_WHO_PROCESS = 1,
IOPRIO_WHO_PGRP,
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
*/
static inline int task_nice_ioprio(struct task_struct *task)
{
return (task_nice(task) + 20) / 5;
}
/*
* This is for the case where the task hasn't asked for a specific IO class.
* Check for idle and rt task process, and return appropriate IO class.
*/
static inline int task_nice_ioclass(struct task_struct *task)
{
if (task->policy == SCHED_IDLE)
return IOPRIO_CLASS_IDLE;
else if (task->policy == SCHED_FIFO || task->policy == SCHED_RR)
return IOPRIO_CLASS_RT;
else
return IOPRIO_CLASS_BE;
}
/*
* For inheritance, return the highest of the two given priorities
*/
extern int ioprio_best(unsigned short aprio, unsigned short bprio);
extern int set_task_ioprio(struct task_struct *task, int ioprio);
#endif