| Message ID | 1564840797-5876-11-git-send-email-suganath-prabu.subramani@broadcom.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | mpt3sas: Features and defect fixes. | expand |
diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c index 9b89fa4..24b5f5f 100644 --- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c +++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c @@ -4670,11 +4670,8 @@ scsih_qcmd(struct Scsi_Host *shost, struct scsi_cmnd *scmd) * since we're lockless at this point */ do { - if (test_bit(0, &sas_device_priv_data->ata_command_pending)) { - scmd->result = SAM_STAT_BUSY; - scmd->scsi_done(scmd); - return 0; - } + if (test_bit(0, &sas_device_priv_data->ata_command_pending)) + return SCSI_MLQUEUE_DEVICE_BUSY; } while (_scsih_set_satl_pending(scmd, true)); if (scmd->sc_data_direction == DMA_FROM_DEVICE)
This patch is to reduce the performance dip depth observed on SATA HDD when ATA PT command is outstanding. Driver returns IO commands with status "SAM_STAT_BUSY" whenever ATA PT command is outstanding. With this, IO commands will be retried until this outstanding ATA PT to complete and hence we will observe dip in performance. As the driver is completing the subsequent IOs commands with SAM_STAT_BUSY status, these IOs has to go though the block layer. Hence it adds latency to the IOs and large performance dip depth is observed. So to reduce this performance dip depth, added improvement in driver to return the subsequent IOs with SCSI_MLQUEUE_DEVICE_BUSY status instead of completing the IOs with SAM_STAT_BUSY status when ATA PT command is outstanding. Sending command back with SCSI_MLQUEUE_DEVICE_BUSY does not go through complete block layer stack (as scsi_done won't be called) SML immediately push the command and this method will avoid latency of Block layer stack and the performance dip depth will be reduced. On Local setup, ran 512k sequential read IO operation on HGST SATA drive with existing driver & with this improvement drivers and here is the result, 1. With existing driver: IOs are running at bandwidth of ~230 rMB/s and whenever any ATA PT command is outstanding (e.g issued from systemd-udevd daemon) then this bandwidth drops to ~150 rMB/s. 2. With this improvement driver: IOs are running at bandwidth of ~230 rMB/s and whenever any ATA PT command is outstanding then this bandwidth drops to just ~190 rMB/s. Signed-off-by: Suganath Prabu <suganath-prabu.subramani@broadcom.com> --- drivers/scsi/mpt3sas/mpt3sas_scsih.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)