From 1faa16d22877f4839bd433547d770c676d1d964c Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 6 Apr 2009 14:48:01 +0200 Subject: block: change the request allocation/congestion logic to be sync/async based This makes sure that we never wait on async IO for sync requests, instead of doing the split on writes vs reads. Signed-off-by: Jens Axboe Signed-off-by: Linus Torvalds --- include/linux/backing-dev.h | 12 +++++------ include/linux/blkdev.h | 52 ++++++++++++++++++++++++++++++--------------- 2 files changed, 41 insertions(+), 23 deletions(-) (limited to 'include') diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index bee52abb8a4d..0ec2c594868e 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -24,8 +24,8 @@ struct dentry; */ enum bdi_state { BDI_pdflush, /* A pdflush thread is working this device */ - BDI_write_congested, /* The write queue is getting full */ - BDI_read_congested, /* The read queue is getting full */ + BDI_async_congested, /* The async (write) queue is getting full */ + BDI_sync_congested, /* The sync queue is getting full */ BDI_unused, /* Available bits start here */ }; @@ -215,18 +215,18 @@ static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits) static inline int bdi_read_congested(struct backing_dev_info *bdi) { - return bdi_congested(bdi, 1 << BDI_read_congested); + return bdi_congested(bdi, 1 << BDI_sync_congested); } static inline int bdi_write_congested(struct backing_dev_info *bdi) { - return bdi_congested(bdi, 1 << BDI_write_congested); + return bdi_congested(bdi, 1 << BDI_async_congested); } static inline int bdi_rw_congested(struct backing_dev_info *bdi) { - return bdi_congested(bdi, (1 << BDI_read_congested)| - (1 << BDI_write_congested)); + return bdi_congested(bdi, (1 << BDI_sync_congested) | + (1 << BDI_async_congested)); } void clear_bdi_congested(struct backing_dev_info *bdi, int rw); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 465d6babc847..67dae3bd881c 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -38,6 +38,10 @@ struct request; typedef void (rq_end_io_fn)(struct request *, int); struct request_list { + /* + * count[], starved[], and wait[] are indexed by + * BLK_RW_SYNC/BLK_RW_ASYNC + */ int count[2]; int starved[2]; int elvpriv; @@ -66,6 +70,11 @@ enum rq_cmd_type_bits { REQ_TYPE_ATA_PC, }; +enum { + BLK_RW_ASYNC = 0, + BLK_RW_SYNC = 1, +}; + /* * For request of type REQ_TYPE_LINUX_BLOCK, rq->cmd[0] is the opcode being * sent down (similar to how REQ_TYPE_BLOCK_PC means that ->cmd[] holds a @@ -103,7 +112,7 @@ enum rq_flag_bits { __REQ_QUIET, /* don't worry about errors */ __REQ_PREEMPT, /* set for "ide_preempt" requests */ __REQ_ORDERED_COLOR, /* is before or after barrier */ - __REQ_RW_SYNC, /* request is sync (O_DIRECT) */ + __REQ_RW_SYNC, /* request is sync (sync write or read) */ __REQ_ALLOCED, /* request came from our alloc pool */ __REQ_RW_META, /* metadata io request */ __REQ_COPY_USER, /* contains copies of user pages */ @@ -438,8 +447,8 @@ struct request_queue #define QUEUE_FLAG_CLUSTER 0 /* cluster several segments into 1 */ #define QUEUE_FLAG_QUEUED 1 /* uses generic tag queueing */ #define QUEUE_FLAG_STOPPED 2 /* queue is stopped */ -#define QUEUE_FLAG_READFULL 3 /* read queue has been filled */ -#define QUEUE_FLAG_WRITEFULL 4 /* write queue has been filled */ +#define QUEUE_FLAG_SYNCFULL 3 /* read queue has been filled */ +#define QUEUE_FLAG_ASYNCFULL 4 /* write queue has been filled */ #define QUEUE_FLAG_DEAD 5 /* queue being torn down */ #define QUEUE_FLAG_REENTER 6 /* Re-entrancy avoidance */ #define QUEUE_FLAG_PLUGGED 7 /* queue is plugged */ @@ -611,32 +620,41 @@ enum { #define rq_data_dir(rq) ((rq)->cmd_flags & 1) /* - * We regard a request as sync, if it's a READ or a SYNC write. + * We regard a request as sync, if either a read or a sync write */ -#define rq_is_sync(rq) (rq_data_dir((rq)) == READ || (rq)->cmd_flags & REQ_RW_SYNC) +static inline bool rw_is_sync(unsigned int rw_flags) +{ + return !(rw_flags & REQ_RW) || (rw_flags & REQ_RW_SYNC); +} + +static inline bool rq_is_sync(struct request *rq) +{ + return rw_is_sync(rq->cmd_flags); +} + #define rq_is_meta(rq) ((rq)->cmd_flags & REQ_RW_META) -static inline int blk_queue_full(struct request_queue *q, int rw) +static inline int blk_queue_full(struct request_queue *q, int sync) { - if (rw == READ) - return test_bit(QUEUE_FLAG_READFULL, &q->queue_flags); - return test_bit(QUEUE_FLAG_WRITEFULL, &q->queue_flags); + if (sync) + return test_bit(QUEUE_FLAG_SYNCFULL, &q->queue_flags); + return test_bit(QUEUE_FLAG_ASYNCFULL, &q->queue_flags); } -static inline void blk_set_queue_full(struct request_queue *q, int rw) +static inline void blk_set_queue_full(struct request_queue *q, int sync) { - if (rw == READ) - queue_flag_set(QUEUE_FLAG_READFULL, q); + if (sync) + queue_flag_set(QUEUE_FLAG_SYNCFULL, q); else - queue_flag_set(QUEUE_FLAG_WRITEFULL, q); + queue_flag_set(QUEUE_FLAG_ASYNCFULL, q); } -static inline void blk_clear_queue_full(struct request_queue *q, int rw) +static inline void blk_clear_queue_full(struct request_queue *q, int sync) { - if (rw == READ) - queue_flag_clear(QUEUE_FLAG_READFULL, q); + if (sync) + queue_flag_clear(QUEUE_FLAG_SYNCFULL, q); else - queue_flag_clear(QUEUE_FLAG_WRITEFULL, q); + queue_flag_clear(QUEUE_FLAG_ASYNCFULL, q); } -- cgit v1.2.3