The patch titled
aic94xx: Increase can_queue and cmds_per_lun
has been added to the -mm tree. Its filename is
aic94xx-increase-can_queue-and-cmds_per_lun.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: aic94xx: Increase can_queue and cmds_per_lun
From: "Darrick J. Wong" <djwong@xxxxxxxxxx>
Set sets cmd_per_lun and can_queue in the aic94xx driver's
scsi_host_template to better performing values than what's there currently.
The cmd_per_lun setting is stolen straight out of the adp94xx source, and
can_queue is derived from the max_scb value that we calculate in
asd_init_hw. To the best of my (admittedly limited) knowledge, this method
provides the correct values (can_queue = 443 in both adp94xx and aic94xx on
my 9405W) but if anybody knows better, please enlighten me. :)
That said, the effect of leaving these values set to 1 is terrible
performance in the case of either (a) certain Maxtor SAS drives flying solo
or (b) flooding several disks with I/O simultaneously (md-raid). There may
be more scenarios where we see similar problems that I haven't uncovered.
Just for grins, I ran bogodisk (an O_DIRECT-enabled read speed test)
against three different scenarios:
1) adp94xx 1.0.8-6, pounded into 2.6.18-rc4 [green]
2) aic94xx 1.0.2, without this patch [red]
3) aic94xx 1.0.2, with this [blue]
...with these results:
http://sweaglesw.net/~djwong/programs/bogodisk/bd_graphs/bad_sas.0.png
As you can see, the read performance is cut in half by the aic94xx driver
not getting a chance to have multiple I/Os in flight at any given time.
With the patch, the two drivers are fairly close bandwidth-wise. Also
thanks to Mike Anderson for helping me figure this out.
Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
drivers/scsi/aic94xx/aic94xx_hwi.h | 3 +++
drivers/scsi/aic94xx/aic94xx_init.c | 10 +++++++---
2 files changed, 10 insertions(+), 3 deletions(-)
diff -puN drivers/scsi/aic94xx/aic94xx_hwi.h~aic94xx-increase-can_queue-and-cmds_per_lun drivers/scsi/aic94xx/aic94xx_hwi.h
--- a/drivers/scsi/aic94xx/aic94xx_hwi.h~aic94xx-increase-can_queue-and-cmds_per_lun
+++ a/drivers/scsi/aic94xx/aic94xx_hwi.h
@@ -36,6 +36,9 @@
#include "aic94xx.h"
#include "aic94xx_sas.h"
+/* Leave a few empty data buffers. */
+#define ASD_FREE_SCBS 3
+
/* Define ASD_MAX_PHYS to the maximum phys ever. Currently 8. */
#define ASD_MAX_PHYS 8
#define ASD_PCBA_SN_SIZE 12
diff -puN drivers/scsi/aic94xx/aic94xx_init.c~aic94xx-increase-can_queue-and-cmds_per_lun drivers/scsi/aic94xx/aic94xx_init.c
--- a/drivers/scsi/aic94xx/aic94xx_init.c~aic94xx-increase-can_queue-and-cmds_per_lun
+++ a/drivers/scsi/aic94xx/aic94xx_init.c
@@ -71,7 +71,7 @@ static struct scsi_host_template aic94xx
.change_queue_type = sas_change_queue_type,
.bios_param = sas_bios_param,
.can_queue = 1,
- .cmd_per_lun = 1,
+ .cmd_per_lun = 2,
.this_id = -1,
.sg_tablesize = SG_ALL,
.max_sectors = SCSI_DEFAULT_MAX_SECTORS,
@@ -612,13 +612,17 @@ static int __devinit asd_pci_probe(struc
goto Err_free_cache;
asd_printk("device %s: SAS addr %llx, PCBA SN %s, %d phys, %d enabled "
- "phys, flash %s, BIOS %s%d\n",
+ "phys, flash %s, BIOS %s%d, SCBs %d\n",
pci_name(dev), SAS_ADDR(asd_ha->hw_prof.sas_addr),
asd_ha->hw_prof.pcba_sn, asd_ha->hw_prof.max_phys,
asd_ha->hw_prof.num_phys,
asd_ha->hw_prof.flash.present ? "present" : "not present",
asd_ha->hw_prof.bios.present ? "build " : "not present",
- asd_ha->hw_prof.bios.bld);
+ asd_ha->hw_prof.bios.bld,
+ asd_ha->hw_prof.max_scbs);
+
+ aic94xx_sht.can_queue = asd_ha->hw_prof.max_scbs - ASD_FREE_SCBS;
+ shost->can_queue = aic94xx_sht.can_queue;
if (use_msi)
pci_enable_msi(asd_ha->pcidev);
_
Patches currently in -mm which might be from djwong@xxxxxxxxxx are
aic94xx-increase-can_queue-and-cmds_per_lun.patch
-
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