svn commit: r228939 - head/sys/dev/mps

[Alexander Motin]

On 09.01.2012 21:04, Garrett Cooper wrote:
> 2012/1/9 Alexander Motin<mav at freebsd.org>:
>> On 09.01.2012 20:54, Maksim Yevmenkin wrote:
>>>
>>> On Wed, Dec 28, 2011 at 2:49 PM, Alexander Motin<mav at freebsd.org>    wrote:
>>>
>>>> Author: mav
>>>> Date: Wed Dec 28 22:49:28 2011
>>>> New Revision: 228939
>>>> URL: http://svn.freebsd.org/changeset/base/228939
>>>>
>>>> Log:
>>>>   Set maximum I/O size for mps(4) to MAXPHYS. Looking into the code, I see
>>>>   no reason why it should be limited to 64K of DFLTPHYS. DMA data tag is
>>>> any
>>>>   way set to allow MAXPHYS, S/G lists (chain elements) are sufficient and
>>>>   overflows are also handled. On my tests even 1MB I/Os are working fine.
>>>>
>>>>   Reviewed by:  ken@
>>>>
>>>> Modified:
>>>>   head/sys/dev/mps/mps_sas.c
>>>>
>>>> Modified: head/sys/dev/mps/mps_sas.c
>>>>
>>>> ==============================================================================
>>>> --- head/sys/dev/mps/mps_sas.c  Wed Dec 28 22:18:53 2011        (r228938)
>>>> +++ head/sys/dev/mps/mps_sas.c  Wed Dec 28 22:49:28 2011        (r228939)
>>>> @@ -937,6 +937,7 @@ mpssas_action(struct cam_sim *sim, union
>>>>                 cpi->transport_version = 0;
>>>>                 cpi->protocol = PROTO_SCSI;
>>>>                 cpi->protocol_version = SCSI_REV_SPC;
>>>> +               cpi->maxio = MAXPHYS;
>>>>                 cpi->ccb_h.status = CAM_REQ_CMP;
>>>>                 break;
>>>>         }
>>>
>>>
>>> sorry for the late reply, but can we make in into tunable please? i
>>> have in local tree
>>>
>>> --- mps_sas.c.orig      2011-11-17 02:05:04.000000000 -0800
>>> +++ mps_sas.c   2011-12-28 16:05:10.000000000 -0800
>>> @@ -121,6 +121,11 @@
>>>
>>>   MALLOC_DEFINE(M_MPSSAS, "MPSSAS", "MPS SAS memory");
>>>
>>> +int mps_maxio = MAXPHYS;
>>> +TUNABLE_INT("hw.mps.maxio",&mps_maxio);
>>> +SYSCTL_INT(_hw_mps, OID_AUTO, maxio, CTLFLAG_RD,&mps_maxio, 0,
>>> +       "CAM maxio override\n");
>>> +
>>>   static __inline int mpssas_set_lun(uint8_t *lun, u_int ccblun);
>>>   static struct mpssas_target * mpssas_alloc_target(struct mpssas_softc *,
>>>       struct mpssas_target *);
>>> @@ -938,6 +943,7 @@
>>>
>>>                 cpi->protocol = PROTO_SCSI;
>>>                 cpi->protocol_version = SCSI_REV_SPC;
>>>                 cpi->ccb_h.status = CAM_REQ_CMP;
>>> +               cpi->maxio = mps_maxio;
>>>                 break;
>>>         }
>>>         case XPT_GET_TRAN_SETTINGS:
>>
>>
>> We can. but could you explain why? Have you found any problems this change?
>
>      It would make it nice when dealing with different controllers -- a
> similar example is that mfi(4) has a tunable called hw.mfi.max_cmds
> which controls the I/O command queue size as not all MegaRAID cards
> have the same I/O queue size capabilities.

Not many people care able to configure such low-level things. It means 
that if such configuration is needed, then either most of others will be 
in trouble or at least get suboptimal performance. If there are any way 
to avoid such tunables, I believe we should avoid them.

-- 
Alexander Motin