Commit ff856bad authored by Jens Axboe's avatar Jens Axboe
Browse files

[BLOCK] ll_rw_blk: Enable out-of-order request completions through softirq



Request completion can be a quite heavy process, since it needs to
iterate through the entire request and complete the bio's it holds.
This patch adds blk_complete_request() which moves this processing
into a dedicated block softirq.
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent 5367f2d6
......@@ -27,6 +27,8 @@
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
/*
* for max sense size
......@@ -62,13 +64,15 @@ static wait_queue_head_t congestion_wqh[2] = {
/*
* Controlling structure to kblockd
*/
static struct workqueue_struct *kblockd_workqueue;
static struct workqueue_struct *kblockd_workqueue;
unsigned long blk_max_low_pfn, blk_max_pfn;
EXPORT_SYMBOL(blk_max_low_pfn);
EXPORT_SYMBOL(blk_max_pfn);
static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
/* Amount of time in which a process may batch requests */
#define BLK_BATCH_TIME (HZ/50UL)
......@@ -207,6 +211,13 @@ void blk_queue_merge_bvec(request_queue_t *q, merge_bvec_fn *mbfn)
EXPORT_SYMBOL(blk_queue_merge_bvec);
void blk_queue_softirq_done(request_queue_t *q, softirq_done_fn *fn)
{
q->softirq_done_fn = fn;
}
EXPORT_SYMBOL(blk_queue_softirq_done);
/**
* blk_queue_make_request - define an alternate make_request function for a device
* @q: the request queue for the device to be affected
......@@ -270,6 +281,7 @@ EXPORT_SYMBOL(blk_queue_make_request);
static inline void rq_init(request_queue_t *q, struct request *rq)
{
INIT_LIST_HEAD(&rq->queuelist);
INIT_LIST_HEAD(&rq->donelist);
rq->errors = 0;
rq->rq_status = RQ_ACTIVE;
......@@ -286,6 +298,7 @@ static inline void rq_init(request_queue_t *q, struct request *rq)
rq->sense = NULL;
rq->end_io = NULL;
rq->end_io_data = NULL;
rq->completion_data = NULL;
}
/**
......@@ -3286,6 +3299,87 @@ int end_that_request_chunk(struct request *req, int uptodate, int nr_bytes)
EXPORT_SYMBOL(end_that_request_chunk);
/*
* splice the completion data to a local structure and hand off to
* process_completion_queue() to complete the requests
*/
static void blk_done_softirq(struct softirq_action *h)
{
struct list_head *cpu_list;
LIST_HEAD(local_list);
local_irq_disable();
cpu_list = &__get_cpu_var(blk_cpu_done);
list_splice_init(cpu_list, &local_list);
local_irq_enable();
while (!list_empty(&local_list)) {
struct request *rq = list_entry(local_list.next, struct request, donelist);
list_del_init(&rq->donelist);
rq->q->softirq_done_fn(rq);
}
}
#ifdef CONFIG_HOTPLUG_CPU
static int blk_cpu_notify(struct notifier_block *self, unsigned long action,
void *hcpu)
{
/*
* If a CPU goes away, splice its entries to the current CPU
* and trigger a run of the softirq
*/
if (action == CPU_DEAD) {
int cpu = (unsigned long) hcpu;
local_irq_disable();
list_splice_init(&per_cpu(blk_cpu_done, cpu),
&__get_cpu_var(blk_cpu_done));
raise_softirq_irqoff(BLOCK_SOFTIRQ);
local_irq_enable();
}
return NOTIFY_OK;
}
static struct notifier_block __devinitdata blk_cpu_notifier = {
.notifier_call = blk_cpu_notify,
};
#endif /* CONFIG_HOTPLUG_CPU */
/**
* blk_complete_request - end I/O on a request
* @req: the request being processed
*
* Description:
* Ends all I/O on a request. It does not handle partial completions,
* unless the driver actually implements this in its completionc callback
* through requeueing. Theh actual completion happens out-of-order,
* through a softirq handler. The user must have registered a completion
* callback through blk_queue_softirq_done().
**/
void blk_complete_request(struct request *req)
{
struct list_head *cpu_list;
unsigned long flags;
BUG_ON(!req->q->softirq_done_fn);
local_irq_save(flags);
cpu_list = &__get_cpu_var(blk_cpu_done);
list_add_tail(&req->donelist, cpu_list);
raise_softirq_irqoff(BLOCK_SOFTIRQ);
local_irq_restore(flags);
}
EXPORT_SYMBOL(blk_complete_request);
/*
* queue lock must be held
*/
......@@ -3364,6 +3458,8 @@ EXPORT_SYMBOL(kblockd_flush);
int __init blk_dev_init(void)
{
int i;
kblockd_workqueue = create_workqueue("kblockd");
if (!kblockd_workqueue)
panic("Failed to create kblockd\n");
......@@ -3377,6 +3473,14 @@ int __init blk_dev_init(void)
iocontext_cachep = kmem_cache_create("blkdev_ioc",
sizeof(struct io_context), 0, SLAB_PANIC, NULL, NULL);
for (i = 0; i < NR_CPUS; i++)
INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL);
#ifdef CONFIG_HOTPLUG_CPU
register_cpu_notifier(&blk_cpu_notifier);
#endif
blk_max_low_pfn = max_low_pfn;
blk_max_pfn = max_pfn;
......
......@@ -118,9 +118,9 @@ struct request_list {
* try to put the fields that are referenced together in the same cacheline
*/
struct request {
struct list_head queuelist; /* looking for ->queue? you must _not_
* access it directly, use
* blkdev_dequeue_request! */
struct list_head queuelist;
struct list_head donelist;
unsigned long flags; /* see REQ_ bits below */
/* Maintain bio traversal state for part by part I/O submission.
......@@ -141,6 +141,7 @@ struct request {
struct bio *biotail;
void *elevator_private;
void *completion_data;
unsigned short ioprio;
......@@ -291,6 +292,7 @@ typedef int (merge_bvec_fn) (request_queue_t *, struct bio *, struct bio_vec *);
typedef void (activity_fn) (void *data, int rw);
typedef int (issue_flush_fn) (request_queue_t *, struct gendisk *, sector_t *);
typedef void (prepare_flush_fn) (request_queue_t *, struct request *);
typedef void (softirq_done_fn)(struct request *);
enum blk_queue_state {
Queue_down,
......@@ -332,6 +334,7 @@ struct request_queue
activity_fn *activity_fn;
issue_flush_fn *issue_flush_fn;
prepare_flush_fn *prepare_flush_fn;
softirq_done_fn *softirq_done_fn;
/*
* Dispatch queue sorting
......@@ -646,6 +649,17 @@ extern int end_that_request_first(struct request *, int, int);
extern int end_that_request_chunk(struct request *, int, int);
extern void end_that_request_last(struct request *, int);
extern void end_request(struct request *req, int uptodate);
extern void blk_complete_request(struct request *);
static inline int rq_all_done(struct request *rq, unsigned int nr_bytes)
{
if (blk_fs_request(rq))
return (nr_bytes >= (rq->hard_nr_sectors << 9));
else if (blk_pc_request(rq))
return nr_bytes >= rq->data_len;
return 0;
}
/*
* end_that_request_first/chunk() takes an uptodate argument. we account
......@@ -694,6 +708,7 @@ extern void blk_queue_segment_boundary(request_queue_t *, unsigned long);
extern void blk_queue_prep_rq(request_queue_t *, prep_rq_fn *pfn);
extern void blk_queue_merge_bvec(request_queue_t *, merge_bvec_fn *);
extern void blk_queue_dma_alignment(request_queue_t *, int);
extern void blk_queue_softirq_done(request_queue_t *, softirq_done_fn *);
extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
extern int blk_queue_ordered(request_queue_t *, unsigned, prepare_flush_fn *);
extern void blk_queue_issue_flush_fn(request_queue_t *, issue_flush_fn *);
......
......@@ -112,6 +112,7 @@ enum
TIMER_SOFTIRQ,
NET_TX_SOFTIRQ,
NET_RX_SOFTIRQ,
BLOCK_SOFTIRQ,
SCSI_SOFTIRQ,
TASKLET_SOFTIRQ
};
......
Supports Markdown
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment