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Subject[PATCH 3/5] scsi: megaraid_sas - throttle io if FW is busy
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Date
Checks added in megasas_queue_command to know if FW is able to process
commands within timeout period. If number of retries is 2 or greater,
the driver stops sending cmd to FW. IO is resumed if pending cmd count
reduces to 16 or 5 seconds has elapsed from the time cmds were last sent
to FW.

Signed-off-by: Sumant Patro <sumant.patro@lsi.com>
---

drivers/scsi/megaraid/megaraid_sas.c | 27 +++++++++++++++++++++++++
drivers/scsi/megaraid/megaraid_sas.h | 3 ++
2 files changed, 30 insertions(+)

diff -uprN 2.6.new-p2/drivers/scsi/megaraid/megaraid_sas.c 2.6.new-p3/drivers/scsi/megaraid/megaraid_sas.c
--- 2.6.new-p2/drivers/scsi/megaraid/megaraid_sas.c 2007-02-06 08:43:40.000000000 -0800
+++ 2.6.new-p3/drivers/scsi/megaraid/megaraid_sas.c 2007-02-06 08:50:40.000000000 -0800
@@ -839,6 +839,7 @@ megasas_queue_command(struct scsi_cmnd *
u32 frame_count;
struct megasas_cmd *cmd;
struct megasas_instance *instance;
+ unsigned long sec;

instance = (struct megasas_instance *)
scmd->device->host->hostdata;
@@ -856,6 +857,23 @@ megasas_queue_command(struct scsi_cmnd *
goto out_done;
}

+ /* Check if we can process cmds */
+ if(instance->is_busy){
+ sec = (jiffies - instance->last_time) / HZ;
+ if(sec<5)
+ return SCSI_MLQUEUE_HOST_BUSY;
+ else{
+ instance->is_busy=0;
+ instance->last_time=0;
+ }
+ }
+
+ if(scmd->retries>1){
+ /* FW is busy */
+ instance->is_busy=1;
+ instance->last_time=jiffies;
+ }
+
cmd = megasas_get_cmd(instance);
if (!cmd)
return SCSI_MLQUEUE_HOST_BUSY;
@@ -1200,6 +1218,7 @@ megasas_complete_cmd(struct megasas_inst
{
int exception = 0;
struct megasas_header *hdr = &cmd->frame->hdr;
+ int outstanding;

if (cmd->scmd) {
cmd->scmd->SCp.ptr = (char *)0;
@@ -1313,6 +1332,12 @@ megasas_complete_cmd(struct megasas_inst
hdr->cmd);
break;
}
+
+ if(instance->is_busy){
+ outstanding = atomic_read(&instance->fw_outstanding);
+ if(outstanding<17)
+ instance->is_busy=0;
+ }
}

/**
@@ -2384,6 +2409,8 @@ megasas_probe_one(struct pci_dev *pdev,
instance->init_id = MEGASAS_DEFAULT_INIT_ID;

megasas_dbg_lvl = 0;
+ instance->is_busy = 0;
+ instance->last_time = 0;

/*
* Initialize MFI Firmware
diff -uprN 2.6.new-p2/drivers/scsi/megaraid/megaraid_sas.h 2.6.new-p3/drivers/scsi/megaraid/megaraid_sas.h
--- 2.6.new-p2/drivers/scsi/megaraid/megaraid_sas.h 2007-02-06 06:56:27.000000000 -0800
+++ 2.6.new-p3/drivers/scsi/megaraid/megaraid_sas.h 2007-02-06 08:51:23.000000000 -0800
@@ -1102,6 +1102,9 @@ struct megasas_instance {
atomic_t fw_outstanding;
u32 hw_crit_error;

+ u8 is_busy;
+ unsigned long last_time;
+
struct megasas_instance_template *instancet;
struct tasklet_struct isr_tasklet;
};
diff -uprN 2.6.new-p2/drivers/scsi/megaraid/megaraid_sas.c 2.6.new-p3/drivers/scsi/megaraid/megaraid_sas.c
--- 2.6.new-p2/drivers/scsi/megaraid/megaraid_sas.c 2007-02-06 08:43:40.000000000 -0800
+++ 2.6.new-p3/drivers/scsi/megaraid/megaraid_sas.c 2007-02-06 08:50:40.000000000 -0800
@@ -839,6 +839,7 @@ megasas_queue_command(struct scsi_cmnd *
u32 frame_count;
struct megasas_cmd *cmd;
struct megasas_instance *instance;
+ unsigned long sec;

instance = (struct megasas_instance *)
scmd->device->host->hostdata;
@@ -856,6 +857,23 @@ megasas_queue_command(struct scsi_cmnd *
goto out_done;
}

+ /* Check if we can process cmds */
+ if(instance->is_busy){
+ sec = (jiffies - instance->last_time) / HZ;
+ if(sec<5)
+ return SCSI_MLQUEUE_HOST_BUSY;
+ else{
+ instance->is_busy=0;
+ instance->last_time=0;
+ }
+ }
+
+ if(scmd->retries>1){
+ /* FW is busy */
+ instance->is_busy=1;
+ instance->last_time=jiffies;
+ }
+
cmd = megasas_get_cmd(instance);
if (!cmd)
return SCSI_MLQUEUE_HOST_BUSY;
@@ -1200,6 +1218,7 @@ megasas_complete_cmd(struct megasas_inst
{
int exception = 0;
struct megasas_header *hdr = &cmd->frame->hdr;
+ int outstanding;

if (cmd->scmd) {
cmd->scmd->SCp.ptr = (char *)0;
@@ -1313,6 +1332,12 @@ megasas_complete_cmd(struct megasas_inst
hdr->cmd);
break;
}
+
+ if(instance->is_busy){
+ outstanding = atomic_read(&instance->fw_outstanding);
+ if(outstanding<17)
+ instance->is_busy=0;
+ }
}

/**
@@ -2384,6 +2409,8 @@ megasas_probe_one(struct pci_dev *pdev,
instance->init_id = MEGASAS_DEFAULT_INIT_ID;

megasas_dbg_lvl = 0;
+ instance->is_busy = 0;
+ instance->last_time = 0;

/*
* Initialize MFI Firmware
diff -uprN 2.6.new-p2/drivers/scsi/megaraid/megaraid_sas.h 2.6.new-p3/drivers/scsi/megaraid/megaraid_sas.h
--- 2.6.new-p2/drivers/scsi/megaraid/megaraid_sas.h 2007-02-06 06:56:27.000000000 -0800
+++ 2.6.new-p3/drivers/scsi/megaraid/megaraid_sas.h 2007-02-06 08:51:23.000000000 -0800
@@ -1102,6 +1102,9 @@ struct megasas_instance {
atomic_t fw_outstanding;
u32 hw_crit_error;

+ u8 is_busy;
+ unsigned long last_time;
+
struct megasas_instance_template *instancet;
struct tasklet_struct isr_tasklet;
};
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