From c1ecb90a66c5afc7cc5c9349f9c3714eef4a5cfb Mon Sep 17 00:00:00 2001 From: Chris Leech Date: Thu, 10 Dec 2009 09:59:26 -0800 Subject: [SCSI] libfc: reduce hold time on SCSI host lock Introduce a new lock to protect the list of fc_fcp_pkt structs in libfc instead of using the host lock. This reduces the contention of this heavily used lock, and I see up to a 25% performance gain in CPU bound small I/O tests when scaling out across multiple quad-core CPUs. The big win is in removing the host lock from the completion path completely, as it does not need to be held around the call to scsi_done. Signed-off-by: Chris Leech Signed-off-by: Robert Love Signed-off-by: James Bottomley --- drivers/scsi/libfc/fc_fcp.c | 65 +++++++++++++++++++++++++-------------------- 1 file changed, 36 insertions(+), 29 deletions(-) (limited to 'drivers/scsi/libfc') diff --git a/drivers/scsi/libfc/fc_fcp.c b/drivers/scsi/libfc/fc_fcp.c index c4b58d042f6f..881d5dfe8c74 100644 --- a/drivers/scsi/libfc/fc_fcp.c +++ b/drivers/scsi/libfc/fc_fcp.c @@ -68,18 +68,20 @@ struct kmem_cache *scsi_pkt_cachep; /** * struct fc_fcp_internal - FCP layer internal data - * @scsi_pkt_pool: Memory pool to draw FCP packets from + * @scsi_pkt_pool: Memory pool to draw FCP packets from + * @scsi_queue_lock: Protects the scsi_pkt_queue * @scsi_pkt_queue: Current FCP packets * @last_can_queue_ramp_down_time: ramp down time * @last_can_queue_ramp_up_time: ramp up time * @max_can_queue: max can_queue size */ struct fc_fcp_internal { - mempool_t *scsi_pkt_pool; - struct list_head scsi_pkt_queue; - unsigned long last_can_queue_ramp_down_time; - unsigned long last_can_queue_ramp_up_time; - int max_can_queue; + mempool_t *scsi_pkt_pool; + spinlock_t scsi_queue_lock; + struct list_head scsi_pkt_queue; + unsigned long last_can_queue_ramp_down_time; + unsigned long last_can_queue_ramp_up_time; + int max_can_queue; }; #define fc_get_scsi_internal(x) ((struct fc_fcp_internal *)(x)->scsi_priv) @@ -410,12 +412,14 @@ static inline struct fc_frame *fc_fcp_frame_alloc(struct fc_lport *lport, unsigned long flags; fp = fc_frame_alloc(lport, len); - if (!fp) { - spin_lock_irqsave(lport->host->host_lock, flags); - fc_fcp_can_queue_ramp_down(lport); - spin_unlock_irqrestore(lport->host->host_lock, flags); - } - return fp; + if (likely(fp)) + return fp; + + /* error case */ + spin_lock_irqsave(lport->host->host_lock, flags); + fc_fcp_can_queue_ramp_down(lport); + spin_unlock_irqrestore(lport->host->host_lock, flags); + return NULL; } /** @@ -990,7 +994,7 @@ static void fc_fcp_cleanup_each_cmd(struct fc_lport *lport, unsigned int id, struct scsi_cmnd *sc_cmd; unsigned long flags; - spin_lock_irqsave(lport->host->host_lock, flags); + spin_lock_irqsave(&si->scsi_queue_lock, flags); restart: list_for_each_entry(fsp, &si->scsi_pkt_queue, list) { sc_cmd = fsp->cmd; @@ -1001,7 +1005,7 @@ restart: continue; fc_fcp_pkt_hold(fsp); - spin_unlock_irqrestore(lport->host->host_lock, flags); + spin_unlock_irqrestore(&si->scsi_queue_lock, flags); if (!fc_fcp_lock_pkt(fsp)) { fc_fcp_cleanup_cmd(fsp, error); @@ -1010,14 +1014,14 @@ restart: } fc_fcp_pkt_release(fsp); - spin_lock_irqsave(lport->host->host_lock, flags); + spin_lock_irqsave(&si->scsi_queue_lock, flags); /* * while we dropped the lock multiple pkts could * have been released, so we have to start over. */ goto restart; } - spin_unlock_irqrestore(lport->host->host_lock, flags); + spin_unlock_irqrestore(&si->scsi_queue_lock, flags); } /** @@ -1035,11 +1039,12 @@ static void fc_fcp_abort_io(struct fc_lport *lport) * @fsp: The FCP packet to send * * Return: Zero for success and -1 for failure - * Locks: Called with the host lock and irqs disabled. + * Locks: Called without locks held */ static int fc_fcp_pkt_send(struct fc_lport *lport, struct fc_fcp_pkt *fsp) { struct fc_fcp_internal *si = fc_get_scsi_internal(lport); + unsigned long flags; int rc; fsp->cmd->SCp.ptr = (char *)fsp; @@ -1049,13 +1054,16 @@ static int fc_fcp_pkt_send(struct fc_lport *lport, struct fc_fcp_pkt *fsp) int_to_scsilun(fsp->cmd->device->lun, (struct scsi_lun *)fsp->cdb_cmd.fc_lun); memcpy(fsp->cdb_cmd.fc_cdb, fsp->cmd->cmnd, fsp->cmd->cmd_len); - list_add_tail(&fsp->list, &si->scsi_pkt_queue); - spin_unlock_irq(lport->host->host_lock); + spin_lock_irqsave(&si->scsi_queue_lock, flags); + list_add_tail(&fsp->list, &si->scsi_pkt_queue); + spin_unlock_irqrestore(&si->scsi_queue_lock, flags); rc = lport->tt.fcp_cmd_send(lport, fsp, fc_fcp_recv); - spin_lock_irq(lport->host->host_lock); - if (rc) + if (unlikely(rc)) { + spin_lock_irqsave(&si->scsi_queue_lock, flags); list_del(&fsp->list); + spin_unlock_irqrestore(&si->scsi_queue_lock, flags); + } return rc; } @@ -1752,6 +1760,7 @@ int fc_queuecommand(struct scsi_cmnd *sc_cmd, void (*done)(struct scsi_cmnd *)) struct fcoe_dev_stats *stats; lport = shost_priv(sc_cmd->device->host); + spin_unlock_irq(lport->host->host_lock); rval = fc_remote_port_chkready(rport); if (rval) { @@ -1834,6 +1843,7 @@ int fc_queuecommand(struct scsi_cmnd *sc_cmd, void (*done)(struct scsi_cmnd *)) rc = SCSI_MLQUEUE_HOST_BUSY; } out: + spin_lock_irq(lport->host->host_lock); return rc; } EXPORT_SYMBOL(fc_queuecommand); @@ -1864,11 +1874,8 @@ static void fc_io_compl(struct fc_fcp_pkt *fsp) lport = fsp->lp; si = fc_get_scsi_internal(lport); - spin_lock_irqsave(lport->host->host_lock, flags); - if (!fsp->cmd) { - spin_unlock_irqrestore(lport->host->host_lock, flags); + if (!fsp->cmd) return; - } /* * if can_queue ramp down is done then try can_queue ramp up @@ -1880,10 +1887,8 @@ static void fc_io_compl(struct fc_fcp_pkt *fsp) sc_cmd = fsp->cmd; fsp->cmd = NULL; - if (!sc_cmd->SCp.ptr) { - spin_unlock_irqrestore(lport->host->host_lock, flags); + if (!sc_cmd->SCp.ptr) return; - } CMD_SCSI_STATUS(sc_cmd) = fsp->cdb_status; switch (fsp->status_code) { @@ -1945,10 +1950,11 @@ static void fc_io_compl(struct fc_fcp_pkt *fsp) break; } + spin_lock_irqsave(&si->scsi_queue_lock, flags); list_del(&fsp->list); + spin_unlock_irqrestore(&si->scsi_queue_lock, flags); sc_cmd->SCp.ptr = NULL; sc_cmd->scsi_done(sc_cmd); - spin_unlock_irqrestore(lport->host->host_lock, flags); /* release ref from initial allocation in queue command */ fc_fcp_pkt_release(fsp); @@ -2216,6 +2222,7 @@ int fc_fcp_init(struct fc_lport *lport) lport->scsi_priv = si; si->max_can_queue = lport->host->can_queue; INIT_LIST_HEAD(&si->scsi_pkt_queue); + spin_lock_init(&si->scsi_queue_lock); si->scsi_pkt_pool = mempool_create_slab_pool(2, scsi_pkt_cachep); if (!si->scsi_pkt_pool) { -- cgit v1.2.3