It isn't necessary to check the host depth in scsi_queue_rq() any more since it has been respected by blk-mq before calling scsi_queue_rq() via getting driver tag. Lots of LUNs may attach to same host and per-host IOPS may reach millions, so we should avoid expensive atomic operations on the host-wide counter in the IO path. This patch implements scsi_host_busy() via blk_mq_tagset_busy_iter() with one scsi command state for reading the count of busy IOs for scsi_mq. It is observed that IOPS is increased by 15% in IO test on scsi_debug (32 LUNs, 32 submit queues, 1024 can_queue, libaio/dio) in a dual-socket system. V2: - introduce SCMD_STATE_INFLIGHT for getting accurate host busy via blk_mq_tagset_busy_iter() - verified that original Jens's report[1] is fixed - verified that SCSI timeout/abort works fine [1] https://www.spinics.net/lists/linux-scsi/msg122867.html [2] V1 & its revert: d772a65d8a6c Revert "scsi: core: avoid host-wide host_busy counter for scsi_mq" 23aa8e69f2c6 Revert "scsi: core: fix scsi_host_queue_ready" 265d59aacbce scsi: core: fix scsi_host_queue_ready 328728630d9f scsi: core: avoid host-wide host_busy counter for scsi_mq Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Ewan D. Milne <emilne@xxxxxxxxxx> Cc: Omar Sandoval <osandov@xxxxxx>, Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>, Cc: James Bottomley <james.bottomley@xxxxxxxxxxxxxxxxxxxxx>, Cc: Christoph Hellwig <hch@xxxxxx>, Cc: Kashyap Desai <kashyap.desai@xxxxxxxxxxxx> Cc: Hannes Reinecke <hare@xxxxxxx> Cc: Laurence Oberman <loberman@xxxxxxxxxx> Cc: Bart Van Assche <bart.vanassche@xxxxxxx> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- drivers/scsi/hosts.c | 19 ++++++++++++++++++- drivers/scsi/scsi.c | 2 +- drivers/scsi/scsi_lib.c | 35 +++++++++++++++++------------------ drivers/scsi/scsi_priv.h | 2 +- include/scsi/scsi_cmnd.h | 1 + include/scsi/scsi_host.h | 1 - 6 files changed, 38 insertions(+), 22 deletions(-) diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c index 55522b7162d3..1d669e47b692 100644 --- a/drivers/scsi/hosts.c +++ b/drivers/scsi/hosts.c @@ -38,6 +38,7 @@ #include <scsi/scsi_device.h> #include <scsi/scsi_host.h> #include <scsi/scsi_transport.h> +#include <scsi/scsi_cmnd.h> #include "scsi_priv.h" #include "scsi_logging.h" @@ -554,13 +555,29 @@ struct Scsi_Host *scsi_host_get(struct Scsi_Host *shost) } EXPORT_SYMBOL(scsi_host_get); +static bool scsi_host_check_in_flight(struct request *rq, void *data, + bool reserved) +{ + int *count = data; + struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq); + + if (test_bit(SCMD_STATE_INFLIGHT, &cmd->state)) + (*count)++; + + return true; +} + /** * scsi_host_busy - Return the host busy counter * @shost: Pointer to Scsi_Host to inc. **/ int scsi_host_busy(struct Scsi_Host *shost) { - return atomic_read(&shost->host_busy); + int cnt = 0; + + blk_mq_tagset_busy_iter(&shost->tag_set, + scsi_host_check_in_flight, &cnt); + return cnt; } EXPORT_SYMBOL(scsi_host_busy); diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c index 1f5b5c8a7f72..ddc4ec6ea2a1 100644 --- a/drivers/scsi/scsi.c +++ b/drivers/scsi/scsi.c @@ -186,7 +186,7 @@ void scsi_finish_command(struct scsi_cmnd *cmd) struct scsi_driver *drv; unsigned int good_bytes; - scsi_device_unbusy(sdev); + scsi_device_unbusy(sdev, cmd); /* * Clear the flags that say that the device/target/host is no longer diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index dc210b9d4896..b6f66dcb15a5 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -189,7 +189,7 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy) * active on the host/device. */ if (unbusy) - scsi_device_unbusy(device); + scsi_device_unbusy(device, cmd); /* * Requeue this command. It will go before all other commands @@ -329,12 +329,12 @@ static void scsi_init_cmd_errh(struct scsi_cmnd *cmd) * host_failed counter or that it notices the shost state change made by * scsi_eh_scmd_add(). */ -static void scsi_dec_host_busy(struct Scsi_Host *shost) +static void scsi_dec_host_busy(struct Scsi_Host *shost, struct scsi_cmnd *cmd) { unsigned long flags; rcu_read_lock(); - atomic_dec(&shost->host_busy); + __clear_bit(SCMD_STATE_INFLIGHT, &cmd->state); if (unlikely(scsi_host_in_recovery(shost))) { spin_lock_irqsave(shost->host_lock, flags); if (shost->host_failed || shost->host_eh_scheduled) @@ -344,12 +344,12 @@ static void scsi_dec_host_busy(struct Scsi_Host *shost) rcu_read_unlock(); } -void scsi_device_unbusy(struct scsi_device *sdev) +void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd) { struct Scsi_Host *shost = sdev->host; struct scsi_target *starget = scsi_target(sdev); - scsi_dec_host_busy(shost); + scsi_dec_host_busy(shost, cmd); if (starget->can_queue > 0) atomic_dec(&starget->target_busy); @@ -430,9 +430,6 @@ static inline bool scsi_target_is_busy(struct scsi_target *starget) static inline bool scsi_host_is_busy(struct Scsi_Host *shost) { - if (shost->can_queue > 0 && - atomic_read(&shost->host_busy) >= shost->can_queue) - return true; if (atomic_read(&shost->host_blocked) > 0) return true; if (shost->host_self_blocked) @@ -1139,6 +1136,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd) unsigned int flags = cmd->flags & SCMD_PRESERVED_FLAGS; unsigned long jiffies_at_alloc; int retries; + bool in_flight; if (!blk_rq_is_scsi(rq) && !(flags & SCMD_INITIALIZED)) { flags |= SCMD_INITIALIZED; @@ -1147,6 +1145,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd) jiffies_at_alloc = cmd->jiffies_at_alloc; retries = cmd->retries; + in_flight = test_bit(SCMD_STATE_INFLIGHT, &cmd->state); /* zero out the cmd, except for the embedded scsi_request */ memset((char *)cmd + sizeof(cmd->req), 0, sizeof(*cmd) - sizeof(cmd->req) + dev->host->hostt->cmd_size); @@ -1158,6 +1157,8 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd) INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler); cmd->jiffies_at_alloc = jiffies_at_alloc; cmd->retries = retries; + if (in_flight) + __set_bit(SCMD_STATE_INFLIGHT, &cmd->state); scsi_add_cmd_to_list(cmd); } @@ -1367,16 +1368,14 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost, */ static inline int scsi_host_queue_ready(struct request_queue *q, struct Scsi_Host *shost, - struct scsi_device *sdev) + struct scsi_device *sdev, + struct scsi_cmnd *cmd) { - unsigned int busy; - if (scsi_host_in_recovery(shost)) return 0; - busy = atomic_inc_return(&shost->host_busy) - 1; if (atomic_read(&shost->host_blocked) > 0) { - if (busy) + if (scsi_host_busy(shost) > 0) goto starved; /* @@ -1390,8 +1389,6 @@ static inline int scsi_host_queue_ready(struct request_queue *q, "unblocking host at zero depth\n")); } - if (shost->can_queue > 0 && busy >= shost->can_queue) - goto starved; if (shost->host_self_blocked) goto starved; @@ -1403,6 +1400,8 @@ static inline int scsi_host_queue_ready(struct request_queue *q, spin_unlock_irq(shost->host_lock); } + __set_bit(SCMD_STATE_INFLIGHT, &cmd->state); + return 1; starved: @@ -1411,7 +1410,7 @@ static inline int scsi_host_queue_ready(struct request_queue *q, list_add_tail(&sdev->starved_entry, &shost->starved_list); spin_unlock_irq(shost->host_lock); out_dec: - scsi_dec_host_busy(shost); + scsi_dec_host_busy(shost, cmd); return 0; } @@ -1665,7 +1664,7 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx, ret = BLK_STS_RESOURCE; if (!scsi_target_queue_ready(shost, sdev)) goto out_put_budget; - if (!scsi_host_queue_ready(q, shost, sdev)) + if (!scsi_host_queue_ready(q, shost, sdev, cmd)) goto out_dec_target_busy; if (!(req->rq_flags & RQF_DONTPREP)) { @@ -1697,7 +1696,7 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx, return BLK_STS_OK; out_dec_host_busy: - scsi_dec_host_busy(shost); + scsi_dec_host_busy(shost, cmd); out_dec_target_busy: if (scsi_target(sdev)->can_queue > 0) atomic_dec(&scsi_target(sdev)->target_busy); diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h index cc2859d76d81..3bff9f7aa684 100644 --- a/drivers/scsi/scsi_priv.h +++ b/drivers/scsi/scsi_priv.h @@ -87,7 +87,7 @@ int scsi_noretry_cmd(struct scsi_cmnd *scmd); extern void scsi_add_cmd_to_list(struct scsi_cmnd *cmd); extern void scsi_del_cmd_from_list(struct scsi_cmnd *cmd); extern int scsi_maybe_unblock_host(struct scsi_device *sdev); -extern void scsi_device_unbusy(struct scsi_device *sdev); +extern void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd); extern void scsi_queue_insert(struct scsi_cmnd *cmd, int reason); extern void scsi_io_completion(struct scsi_cmnd *, unsigned int); extern void scsi_run_host_queues(struct Scsi_Host *shost); diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h index 91bd749a02f7..9c22e85902ec 100644 --- a/include/scsi/scsi_cmnd.h +++ b/include/scsi/scsi_cmnd.h @@ -63,6 +63,7 @@ struct scsi_pointer { /* for scmd->state */ #define SCMD_STATE_COMPLETE 0 +#define SCMD_STATE_INFLIGHT 1 struct scsi_cmnd { struct scsi_request req; diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h index 31e0d6ca1eba..b3fa32df40f8 100644 --- a/include/scsi/scsi_host.h +++ b/include/scsi/scsi_host.h @@ -551,7 +551,6 @@ struct Scsi_Host { /* Area to keep a shared tag map */ struct blk_mq_tag_set tag_set; - atomic_t host_busy; /* commands actually active on low-level */ atomic_t host_blocked; unsigned int host_failed; /* commands that failed. -- 2.20.1
