kernel_optimize_test/block/blk-ioc.c
Vivek Goyal 4cbadbd16e blk-cgroup: Initialize ioc->cgroup_changed at ioc creation time
If we don't explicitly initialize it to zero, CFQ might think that
cgroup of ioc has changed and it generates lots of unnecessary calls
to call_for_each_cic(changed_cgroup). Fix it.

cfq_get_io_context()
  cfq_ioc_set_cgroup()
     call_for_each_cic(ioc, changed_cgroup)

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2011-05-23 19:35:04 +02:00

165 lines
3.7 KiB
C

/*
* Functions related to io context handling
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
#include <linux/slab.h>
#include "blk.h"
/*
* For io context allocations
*/
static struct kmem_cache *iocontext_cachep;
static void cfq_dtor(struct io_context *ioc)
{
if (!hlist_empty(&ioc->cic_list)) {
struct cfq_io_context *cic;
cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
cic_list);
cic->dtor(ioc);
}
}
/*
* IO Context helper functions. put_io_context() returns 1 if there are no
* more users of this io context, 0 otherwise.
*/
int put_io_context(struct io_context *ioc)
{
if (ioc == NULL)
return 1;
BUG_ON(atomic_long_read(&ioc->refcount) == 0);
if (atomic_long_dec_and_test(&ioc->refcount)) {
rcu_read_lock();
cfq_dtor(ioc);
rcu_read_unlock();
kmem_cache_free(iocontext_cachep, ioc);
return 1;
}
return 0;
}
EXPORT_SYMBOL(put_io_context);
static void cfq_exit(struct io_context *ioc)
{
rcu_read_lock();
if (!hlist_empty(&ioc->cic_list)) {
struct cfq_io_context *cic;
cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
cic_list);
cic->exit(ioc);
}
rcu_read_unlock();
}
/* Called by the exiting task */
void exit_io_context(struct task_struct *task)
{
struct io_context *ioc;
task_lock(task);
ioc = task->io_context;
task->io_context = NULL;
task_unlock(task);
if (atomic_dec_and_test(&ioc->nr_tasks))
cfq_exit(ioc);
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_long_set(&ret->refcount, 1);
atomic_set(&ret->nr_tasks, 1);
spin_lock_init(&ret->lock);
ret->ioprio_changed = 0;
ret->ioprio = 0;
ret->last_waited = 0; /* doesn't matter... */
ret->nr_batch_requests = 0; /* because this is 0 */
INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
INIT_HLIST_HEAD(&ret->cic_list);
ret->ioc_data = NULL;
#if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)
ret->cgroup_changed = 0;
#endif
}
return ret;
}
/*
* If the current task has no IO context then create one and initialise it.
* Otherwise, return its existing IO context.
*
* This returned IO context doesn't have a specifically elevated refcount,
* but since the current task itself holds a reference, the context can be
* used in general code, so long as it stays within `current` context.
*/
struct io_context *current_io_context(gfp_t gfp_flags, int node)
{
struct task_struct *tsk = current;
struct io_context *ret;
ret = tsk->io_context;
if (likely(ret))
return ret;
ret = alloc_io_context(gfp_flags, node);
if (ret) {
/* make sure set_task_ioprio() sees the settings above */
smp_wmb();
tsk->io_context = ret;
}
return ret;
}
/*
* If the current task has no IO context then create one and initialise it.
* If it does have a context, take a ref on it.
*
* This is always called in the context of the task which submitted the I/O.
*/
struct io_context *get_io_context(gfp_t gfp_flags, int node)
{
struct io_context *ret = NULL;
/*
* Check for unlikely race with exiting task. ioc ref count is
* zero when ioc is being detached.
*/
do {
ret = current_io_context(gfp_flags, node);
if (unlikely(!ret))
break;
} while (!atomic_long_inc_not_zero(&ret->refcount));
return ret;
}
EXPORT_SYMBOL(get_io_context);
static int __init blk_ioc_init(void)
{
iocontext_cachep = kmem_cache_create("blkdev_ioc",
sizeof(struct io_context), 0, SLAB_PANIC, NULL);
return 0;
}
subsys_initcall(blk_ioc_init);