[PATCH 1/6] ioprio: move io priority from task_struct to io_context

From: Jens Axboe
Date: Tue Jan 22 2008 - 04:55:54 EST

This is where it belongs and then it doesn't take up space for a
process that doesn't do IO.

Signed-off-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
---
block/cfq-iosched.c | 34 +++++++++----------
block/ll_rw_blk.c | 42 ++++++++++++++++-------
fs/ioprio.c | 29 ++++++++++++----
include/linux/blkdev.h | 75 +------------------------------------------
include/linux/init_task.h | 1 -
include/linux/iocontext.h | 79 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/ioprio.h | 13 ++++---
include/linux/sched.h | 1 -
kernel/fork.c | 31 +++++++++++++++---
9 files changed, 179 insertions(+), 126 deletions(-)
create mode 100644 include/linux/iocontext.h

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 13553e0..533af75 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -199,7 +199,7 @@ CFQ_CFQQ_FNS(sync);

static void cfq_dispatch_insert(struct request_queue *, struct request *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
- struct task_struct *, gfp_t);
+ struct io_context *, gfp_t);
static struct cfq_io_context *cfq_cic_rb_lookup(struct cfq_data *,
struct io_context *);

@@ -1273,7 +1273,7 @@ cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
return cic;
}

-static void cfq_init_prio_data(struct cfq_queue *cfqq)
+static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
{
struct task_struct *tsk = current;
int ioprio_class;
@@ -1281,7 +1281,7 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq)
if (!cfq_cfqq_prio_changed(cfqq))
return;

- ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
+ ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
switch (ioprio_class) {
default:
printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
@@ -1293,11 +1293,11 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq)
cfqq->ioprio_class = IOPRIO_CLASS_BE;
break;
case IOPRIO_CLASS_RT:
- cfqq->ioprio = task_ioprio(tsk);
+ cfqq->ioprio = task_ioprio(ioc);
cfqq->ioprio_class = IOPRIO_CLASS_RT;
break;
case IOPRIO_CLASS_BE:
- cfqq->ioprio = task_ioprio(tsk);
+ cfqq->ioprio = task_ioprio(ioc);
cfqq->ioprio_class = IOPRIO_CLASS_BE;
break;
case IOPRIO_CLASS_IDLE:
@@ -1330,8 +1330,7 @@ static inline void changed_ioprio(struct cfq_io_context *cic)
cfqq = cic->cfqq[ASYNC];
if (cfqq) {
struct cfq_queue *new_cfqq;
- new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc->task,
- GFP_ATOMIC);
+ new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc, GFP_ATOMIC);
if (new_cfqq) {
cic->cfqq[ASYNC] = new_cfqq;
cfq_put_queue(cfqq);
@@ -1363,13 +1362,13 @@ static void cfq_ioc_set_ioprio(struct io_context *ioc)

static struct cfq_queue *
cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
- struct task_struct *tsk, gfp_t gfp_mask)
+ struct io_context *ioc, gfp_t gfp_mask)
{
struct cfq_queue *cfqq, *new_cfqq = NULL;
struct cfq_io_context *cic;

retry:
- cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+ cic = cfq_cic_rb_lookup(cfqd, ioc);
/* cic always exists here */
cfqq = cic_to_cfqq(cic, is_sync);

@@ -1412,7 +1411,7 @@ retry:
cfq_mark_cfqq_prio_changed(cfqq);
cfq_mark_cfqq_queue_new(cfqq);

- cfq_init_prio_data(cfqq);
+ cfq_init_prio_data(cfqq, ioc);
}

if (new_cfqq)
@@ -1439,11 +1438,11 @@ cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
}

static struct cfq_queue *
-cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
+cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
gfp_t gfp_mask)
{
- const int ioprio = task_ioprio(tsk);
- const int ioprio_class = task_ioprio_class(tsk);
+ const int ioprio = task_ioprio(ioc);
+ const int ioprio_class = task_ioprio_class(ioc);
struct cfq_queue **async_cfqq = NULL;
struct cfq_queue *cfqq = NULL;

@@ -1453,7 +1452,7 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
}

if (!cfqq) {
- cfqq = cfq_find_alloc_queue(cfqd, is_sync, tsk, gfp_mask);
+ cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
if (!cfqq)
return NULL;
}
@@ -1793,7 +1792,7 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq = RQ_CFQQ(rq);

- cfq_init_prio_data(cfqq);
+ cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);

cfq_add_rq_rb(rq);

@@ -1900,7 +1899,7 @@ static int cfq_may_queue(struct request_queue *q, int rw)

cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
if (cfqq) {
- cfq_init_prio_data(cfqq);
+ cfq_init_prio_data(cfqq, cic->ioc);
cfq_prio_boost(cfqq);

return __cfq_may_queue(cfqq);
@@ -1938,7 +1937,6 @@ static int
cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
- struct task_struct *tsk = current;
struct cfq_io_context *cic;
const int rw = rq_data_dir(rq);
const int is_sync = rq_is_sync(rq);
@@ -1956,7 +1954,7 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)

cfqq = cic_to_cfqq(cic, is_sync);
if (!cfqq) {
- cfqq = cfq_get_queue(cfqd, is_sync, tsk, gfp_mask);
+ cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);

if (!cfqq)
goto queue_fail;
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 8b91994..bcd0354 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -3882,6 +3882,26 @@ void exit_io_context(void)
put_io_context(ioc);
}

+struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
+{
+ struct io_context *ret;
+
+ ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
+ if (ret) {
+ atomic_set(&ret->refcount, 1);
+ ret->task = current;
+ ret->ioprio_changed = 0;
+ ret->ioprio = 0;
+ ret->last_waited = jiffies; /* doesn't matter... */
+ ret->nr_batch_requests = 0; /* because this is 0 */
+ ret->aic = NULL;
+ ret->cic_root.rb_node = NULL;
+ ret->ioc_data = NULL;
+ }
+
+ return ret;
+}
+
/*
* If the current task has no IO context then create one and initialise it.
* Otherwise, return its existing IO context.
@@ -3899,16 +3919,8 @@ static struct io_context *current_io_context(gfp_t gfp_flags, int node)
if (likely(ret))
return ret;

- ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
+ ret = alloc_io_context(gfp_flags, node);
if (ret) {
- atomic_set(&ret->refcount, 1);
- ret->task = current;
- ret->ioprio_changed = 0;
- ret->last_waited = jiffies; /* doesn't matter... */
- ret->nr_batch_requests = 0; /* because this is 0 */
- ret->aic = NULL;
- ret->cic_root.rb_node = NULL;
- ret->ioc_data = NULL;
/* make sure set_task_ioprio() sees the settings above */
smp_wmb();
tsk->io_context = ret;
@@ -3925,10 +3937,14 @@ static struct io_context *current_io_context(gfp_t gfp_flags, int node)
*/
struct io_context *get_io_context(gfp_t gfp_flags, int node)
{
- struct io_context *ret;
- ret = current_io_context(gfp_flags, node);
- if (likely(ret))
- atomic_inc(&ret->refcount);
+ struct io_context *ret = NULL;
+
+ do {
+ ret = current_io_context(gfp_flags, node);
+ if (unlikely(!ret))
+ break;
+ } while (!atomic_inc_not_zero(&ret->refcount));
+
return ret;
}
EXPORT_SYMBOL(get_io_context);
diff --git a/fs/ioprio.c b/fs/ioprio.c
index e4e01bc..a760040 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -41,18 +41,29 @@ static int set_task_ioprio(struct task_struct *task, int ioprio)
return err;

task_lock(task);
+ do {
+ ioc = task->io_context;
+ /* see wmb() in current_io_context() */
+ smp_read_barrier_depends();
+ if (ioc)
+ break;

- task->ioprio = ioprio;
-
- ioc = task->io_context;
- /* see wmb() in current_io_context() */
- smp_read_barrier_depends();
+ ioc = alloc_io_context(GFP_ATOMIC, -1);
+ if (!ioc) {
+ err = -ENOMEM;
+ break;
+ }
+ task->io_context = ioc;
+ ioc->task = task;
+ } while (1);

- if (ioc)
+ if (!err) {
+ ioc->ioprio = ioprio;
ioc->ioprio_changed = 1;
+ }

task_unlock(task);
- return 0;
+ return err;
}

asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
@@ -148,7 +159,9 @@ static int get_task_ioprio(struct task_struct *p)
ret = security_task_getioprio(p);
if (ret)
goto out;
- ret = p->ioprio;
+ ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
+ if (p->io_context)
+ ret = p->io_context->ioprio;
out:
return ret;
}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d18ee67..d61c6f5 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -34,83 +34,10 @@ struct sg_io_hdr;
#define BLKDEV_MIN_RQ 4
#define BLKDEV_MAX_RQ 128 /* Default maximum */

-/*
- * This is the per-process anticipatory I/O scheduler state.
- */
-struct as_io_context {
- spinlock_t lock;
-
- void (*dtor)(struct as_io_context *aic); /* destructor */
- void (*exit)(struct as_io_context *aic); /* called on task exit */
-
- unsigned long state;
- atomic_t nr_queued; /* queued reads & sync writes */
- atomic_t nr_dispatched; /* number of requests gone to the drivers */
-
- /* IO History tracking */
- /* Thinktime */
- unsigned long last_end_request;
- unsigned long ttime_total;
- unsigned long ttime_samples;
- unsigned long ttime_mean;
- /* Layout pattern */
- unsigned int seek_samples;
- sector_t last_request_pos;
- u64 seek_total;
- sector_t seek_mean;
-};
-
-struct cfq_queue;
-struct cfq_io_context {
- struct rb_node rb_node;
- void *key;
-
- struct cfq_queue *cfqq[2];
-
- struct io_context *ioc;
-
- unsigned long last_end_request;
- sector_t last_request_pos;
-
- unsigned long ttime_total;
- unsigned long ttime_samples;
- unsigned long ttime_mean;
-
- unsigned int seek_samples;
- u64 seek_total;
- sector_t seek_mean;
-
- struct list_head queue_list;
-
- void (*dtor)(struct io_context *); /* destructor */
- void (*exit)(struct io_context *); /* called on task exit */
-};
-
-/*
- * This is the per-process I/O subsystem state. It is refcounted and
- * kmalloc'ed. Currently all fields are modified in process io context
- * (apart from the atomic refcount), so require no locking.
- */
-struct io_context {
- atomic_t refcount;
- struct task_struct *task;
-
- unsigned int ioprio_changed;
-
- /*
- * For request batching
- */
- unsigned long last_waited; /* Time last woken after wait for request */
- int nr_batch_requests; /* Number of requests left in the batch */
-
- struct as_io_context *aic;
- struct rb_root cic_root;
- void *ioc_data;
-};
-
void put_io_context(struct io_context *ioc);
void exit_io_context(void);
struct io_context *get_io_context(gfp_t gfp_flags, int node);
+struct io_context *alloc_io_context(gfp_t, int);
void copy_io_context(struct io_context **pdst, struct io_context **psrc);
void swap_io_context(struct io_context **ioc1, struct io_context **ioc2);

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index cae35b6..7011480 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -133,7 +133,6 @@ extern struct group_info init_groups;
.mm = NULL, \
.active_mm = &init_mm, \
.run_list = LIST_HEAD_INIT(tsk.run_list), \
- .ioprio = 0, \
.time_slice = HZ, \
.tasks = LIST_HEAD_INIT(tsk.tasks), \
.ptrace_children= LIST_HEAD_INIT(tsk.ptrace_children), \
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
new file mode 100644
index 0000000..186807e
--- /dev/null
+++ b/include/linux/iocontext.h
@@ -0,0 +1,79 @@
+#ifndef IOCONTEXT_H
+#define IOCONTEXT_H
+
+/*
+ * This is the per-process anticipatory I/O scheduler state.
+ */
+struct as_io_context {
+ spinlock_t lock;
+
+ void (*dtor)(struct as_io_context *aic); /* destructor */
+ void (*exit)(struct as_io_context *aic); /* called on task exit */
+
+ unsigned long state;
+ atomic_t nr_queued; /* queued reads & sync writes */
+ atomic_t nr_dispatched; /* number of requests gone to the drivers */
+
+ /* IO History tracking */
+ /* Thinktime */
+ unsigned long last_end_request;
+ unsigned long ttime_total;
+ unsigned long ttime_samples;
+ unsigned long ttime_mean;
+ /* Layout pattern */
+ unsigned int seek_samples;
+ sector_t last_request_pos;
+ u64 seek_total;
+ sector_t seek_mean;
+};
+
+struct cfq_queue;
+struct cfq_io_context {
+ struct rb_node rb_node;
+ void *key;
+
+ struct cfq_queue *cfqq[2];
+
+ struct io_context *ioc;
+
+ unsigned long last_end_request;
+ sector_t last_request_pos;
+
+ unsigned long ttime_total;
+ unsigned long ttime_samples;
+ unsigned long ttime_mean;
+
+ unsigned int seek_samples;
+ u64 seek_total;
+ sector_t seek_mean;
+
+ struct list_head queue_list;
+
+ void (*dtor)(struct io_context *); /* destructor */
+ void (*exit)(struct io_context *); /* called on task exit */
+};
+
+/*
+ * This is the per-process I/O subsystem state. It is refcounted and
+ * kmalloc'ed. Currently all fields are modified in process io context
+ * (apart from the atomic refcount), so require no locking.
+ */
+struct io_context {
+ atomic_t refcount;
+ struct task_struct *task;
+
+ unsigned short ioprio;
+ unsigned short ioprio_changed;
+
+ /*
+ * For request batching
+ */
+ unsigned long last_waited; /* Time last woken after wait for request */
+ int nr_batch_requests; /* Number of requests left in the batch */
+
+ struct as_io_context *aic;
+ struct rb_root cic_root;
+ void *ioc_data;
+};
+
+#endif
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index baf2938..2a3bb1b 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -2,6 +2,7 @@
#define IOPRIO_H

#include <linux/sched.h>
+#include <linux/iocontext.h>

/*
* Gives us 8 prio classes with 13-bits of data for each class
@@ -45,18 +46,18 @@ enum {
* the cpu scheduler nice value to an io priority
*/
#define IOPRIO_NORM (4)
-static inline int task_ioprio(struct task_struct *task)
+static inline int task_ioprio(struct io_context *ioc)
{
- if (ioprio_valid(task->ioprio))
- return IOPRIO_PRIO_DATA(task->ioprio);
+ if (ioprio_valid(ioc->ioprio))
+ return IOPRIO_PRIO_DATA(ioc->ioprio);

return IOPRIO_NORM;
}

-static inline int task_ioprio_class(struct task_struct *task)
+static inline int task_ioprio_class(struct io_context *ioc)
{
- if (ioprio_valid(task->ioprio))
- return IOPRIO_PRIO_CLASS(task->ioprio);
+ if (ioprio_valid(ioc->ioprio))
+ return IOPRIO_PRIO_CLASS(ioc->ioprio);

return IOPRIO_CLASS_BE;
}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index cc14656..638250c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -939,7 +939,6 @@ struct task_struct {
struct hlist_head preempt_notifiers;
#endif

- unsigned short ioprio;
/*
* fpu_counter contains the number of consecutive context switches
* that the FPU is used. If this is over a threshold, the lazy fpu
diff --git a/kernel/fork.c b/kernel/fork.c
index 8dd8ff2..9961fb7 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -51,6 +51,7 @@
#include <linux/random.h>
#include <linux/tty.h>
#include <linux/proc_fs.h>
+#include <linux/blkdev.h>

#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -791,6 +792,25 @@ out:
return error;
}

+static int copy_io(struct task_struct *tsk)
+{
+ struct io_context *ioc = current->io_context;
+
+ if (!ioc)
+ return 0;
+
+ if (ioprio_valid(ioc->ioprio)) {
+ tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
+ if (unlikely(!tsk->io_context))
+ return -ENOMEM;
+
+ tsk->io_context->task = tsk;
+ tsk->io_context->ioprio = ioc->ioprio;
+ }
+
+ return 0;
+}
+
/*
* Helper to unshare the files of the current task.
* We don't want to expose copy_files internals to
@@ -1147,15 +1167,17 @@ static struct task_struct *copy_process(unsigned long clone_flags,
goto bad_fork_cleanup_mm;
if ((retval = copy_namespaces(clone_flags, p)))
goto bad_fork_cleanup_keys;
+ if ((retval = copy_io(p)))
+ goto bad_fork_cleanup_namespaces;
retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
if (retval)
- goto bad_fork_cleanup_namespaces;
+ goto bad_fork_cleanup_io;

if (pid != &init_struct_pid) {
retval = -ENOMEM;
pid = alloc_pid(task_active_pid_ns(p));
if (!pid)
- goto bad_fork_cleanup_namespaces;
+ goto bad_fork_cleanup_io;

if (clone_flags & CLONE_NEWPID) {
retval = pid_ns_prepare_proc(task_active_pid_ns(p));
@@ -1224,9 +1246,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
/* Need tasklist lock for parent etc handling! */
write_lock_irq(&tasklist_lock);

- /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */
- p->ioprio = current->ioprio;
-
/*
* The task hasn't been attached yet, so its cpus_allowed mask will
* not be changed, nor will its assigned CPU.
@@ -1317,6 +1336,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
bad_fork_free_pid:
if (pid != &init_struct_pid)
free_pid(pid);
+bad_fork_cleanup_io:
+ put_io_context(p->io_context);
bad_fork_cleanup_namespaces:
exit_task_namespaces(p);
bad_fork_cleanup_keys:
--
1.5.4.rc2.84.gf85fd

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