Increasing SCSI_MAX_PHYS_SEGMENTS to 256 has doubled the IO size to 1MB.
Thanks to all!
cheers - jc
Mike Christie wrote:
>
> john clyne wrote:
>> Can anyone give me some guidance on where in the IO stack I might be
>> running
>> into a 512KB limit on IO transfer sizes to an external FC device? I've
>> checked IO scheduler parameter
>> (/sys/block/<dev>/queue/{max_sectors_kb,max_hw_sectors_kb}. Both are set
>> to
>> 32767. I'm using Qlogic HBAs (qla2312), but I don't see any relevent
>> parameters. I'm running RHEL 4.0 with a 2.6.9-34 kernel. Any pointers
>> would
>> be greatly appreciated.
>>
>
> There are also scatterlist limits.
>
> /sys/class/scsi_host/hostX/sg_tablesize is a limit for the number of
> scatter list entries. For qla2xxx it is 255.
>
> The scsi layer sets the queue's max_phys_segments to 128 by default. I
> thought there was ia scsi compile time option to increase this, but
> maybe you have to just modify the SCSI_MAX_PHYS_SEGMENTS define by hand.
>
> So with the default value and with 4 K pages if you end up getting pages
> that cannot be clustered you will end up with 4K * 128.
> -
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to [EMAIL PROTECTED]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
--
View this message in context:
http://www.nabble.com/IO-transfer-limits-tf2953389.html#a8307532
Sent from the linux-scsi mailing list archive at Nabble.com.
-
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
