Number Of commands in SCSI Miniport Driver

NTDEV
1

hi all,
I am working on a SCSI miniport driver. I am trying to get better
performance from my driver and my bottle neck is Number of commands I get
from PORT driver.

Questions:-

1> How can I tune my driver to receive more number of commands.???
2> What are the factors on which number of commands received by Miniport
depends.??
NOTE: For every command I complete I call next request.I am having a SRB
extension to keep context for every command.
3> How are SRBs allocated by port driver?? from which memory pool?? Does the
size of SRB Extension has to do something with number of SRBs that port
driver can allocate.

Any help is highly appreciated.
thanks
ajitabh

2

Search the MSDN Library or the MS’s site for “NumberOfRequests” or for “Q240314”.

SRBs are allocated by the class drivers like Disk.sys, while SRB extensions are allocated by SCSIPORT by splitting the huge DMA common buffer to pieces. That’s why miniports can run DMA over SRB extensions and ScsiPortGetPhysicalAddress work for them.

Max

----- Original Message -----
From: Saxena, Ajitabh Prakash
To: NT Developers Interest List
Sent: Tuesday, March 18, 2003 6:49 PM
Subject: [ntdev] Number Of commands in SCSI Miniport Driver

hi all,
I am working on a SCSI miniport driver. I am trying to get better performance from my driver and my bottle neck is Number of commands I get from PORT driver.

Questions:-

1> How can I tune my driver to receive more number of commands.???
2> What are the factors on which number of commands received by Miniport depends.??
NOTE: For every command I complete I call next request.I am having a SRB extension to keep context for every command.
3> How are SRBs allocated by port driver?? from which memory pool?? Does the size of SRB Extension has to do something with number of SRBs that port driver can allocate.

Any help is highly appreciated.
thanks
ajitabh

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3

Thanks MAX,
I searched MSDN for ID: Q240314 and found that the following
registry entry might be helpful for me.My only concern now is that is this
entry valid for windows 2000 also since MSDN says that this is for windows
NT 4.0.
The following is the entry :

HKEY_LOCAL_MACHINE\
System\
CurrentControlSet\
Services\
DriverName\
Parameters\
DeviceX\
NumberOfRequests

Thanks
ajitabh

-----Original Message-----
From: Maxim S. Shatskih [mailto:xxxxx@storagecraft.com]
Sent: Tuesday, March 18, 2003 2:59 PM
To: NT Developers Interest List
Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver

Search the MSDN Library or the MS’s site for “NumberOfRequests” or for
“Q240314”.

SRBs are allocated by the class drivers like Disk.sys, while SRB extensions
are allocated by SCSIPORT by splitting the huge DMA common buffer to pieces.
That’s why miniports can run DMA over SRB extensions and
ScsiPortGetPhysicalAddress work for them.

Max

----- Original Message -----
From: Saxena, Ajitabh mailto:xxxxx Prakash
To: NT Developers Interest List mailto:xxxxx
Sent: Tuesday, March 18, 2003 6:49 PM
Subject: [ntdev] Number Of commands in SCSI Miniport Driver

hi all,
I am working on a SCSI miniport driver. I am trying to get better
performance from my driver and my bottle neck is Number of commands I get
from PORT driver.

Questions:-

1> How can I tune my driver to receive more number of commands.???
2> What are the factors on which number of commands received by Miniport
depends.??
NOTE: For every command I complete I call next request.I am having a SRB
extension to keep context for every command.
3> How are SRBs allocated by port driver?? from which memory pool?? Does the
size of SRB Extension has to do something with number of SRBs that port
driver can allocate.

Any help is highly appreciated.
thanks
ajitabh

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4

Yes, valid for w2k too.

----- Original Message -----
From: Saxena, Ajitabh Prakash
To: NT Developers Interest List
Sent: Tuesday, March 18, 2003 11:18 PM
Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver

Thanks MAX,
I searched MSDN for ID: Q240314 and found that the following registry entry might be helpful for me.My only concern now is that is this entry valid for windows 2000 also since MSDN says that this is for windows NT 4.0.
The following is the entry :

HKEY_LOCAL_MACHINE\
System\
CurrentControlSet\
Services\
DriverName\
Parameters\
DeviceX\
NumberOfRequests

Thanks
ajitabh

-----Original Message-----
From: Maxim S. Shatskih [mailto:xxxxx@storagecraft.com]
Sent: Tuesday, March 18, 2003 2:59 PM
To: NT Developers Interest List
Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver

Search the MSDN Library or the MS’s site for “NumberOfRequests” or for “Q240314”.

SRBs are allocated by the class drivers like Disk.sys, while SRB extensions are allocated by SCSIPORT by splitting the huge DMA common buffer to pieces. That’s why miniports can run DMA over SRB extensions and ScsiPortGetPhysicalAddress work for them.

Max

----- Original Message -----
From: Saxena, Ajitabh Prakash
To: NT Developers Interest List
Sent: Tuesday, March 18, 2003 6:49 PM
Subject: [ntdev] Number Of commands in SCSI Miniport Driver

hi all,
I am working on a SCSI miniport driver. I am trying to get better performance from my driver and my bottle neck is Number of commands I get from PORT driver.

Questions:-

1> How can I tune my driver to receive more number of commands.???
2> What are the factors on which number of commands received by Miniport depends.??
NOTE: For every command I complete I call next request.I am having a SRB extension to keep context for every command.
3> How are SRBs allocated by port driver?? from which memory pool?? Does the size of SRB Extension has to do something with number of SRBs that port driver can allocate.

Any help is highly appreciated.
thanks
ajitabh

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5

Its still valid. There are limits to what you can put in for values - 16
at the bottom and 255 at the top. I think storport relaxes the upper
value limit.

===========================
Mark Roddy
Consultant, Microsoft DDK MVP
Hollis Technology Solutions
xxxxx@hollistech.com
www.hollistech.com
603-321-1032

-----Original Message-----
From: “Saxena, Ajitabh Prakash”
To: “NT Developers Interest List”
Date: Tue, 18 Mar 2003 15:18:32 -0500
Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver

> Thanks MAX,
> I searched MSDN for ID: Q240314 and found that the following
> registry entry might be helpful for me.My only concern now is that is
> this
> entry valid for windows 2000 also since MSDN says that this is for
> windows
> NT 4.0.
> The following is the entry :
>
> HKEY_LOCAL_MACHINE\
> System\
> CurrentControlSet\
> Services\
> DriverName\
> Parameters\
> DeviceX\
> NumberOfRequests
>
> Thanks
> ajitabh
>
>
> -----Original Message-----
> From: Maxim S. Shatskih [mailto:xxxxx@storagecraft.com]
> Sent: Tuesday, March 18, 2003 2:59 PM
> To: NT Developers Interest List
> Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver
>
>
> Search the MSDN Library or the MS’s site for “NumberOfRequests” or for
> “Q240314”.
>
> SRBs are allocated by the class drivers like Disk.sys, while SRB
> extensions
> are allocated by SCSIPORT by splitting the huge DMA common buffer to
> pieces.
> That’s why miniports can run DMA over SRB extensions and
> ScsiPortGetPhysicalAddress work for them.
>
> Max
>
>
> ----- Original Message -----
> From: Saxena, Ajitabh mailto:xxxxx Prakash
> To: NT Developers Interest List mailto:xxxxx
> Sent: Tuesday, March 18, 2003 6:49 PM
> Subject: [ntdev] Number Of commands in SCSI Miniport Driver
>
>
> hi all,
> I am working on a SCSI miniport driver. I am trying to get better
> performance from my driver and my bottle neck is Number of commands I
> get
> from PORT driver.
>
> Questions:-
>
> 1> How can I tune my driver to receive more number of commands.???
> 2> What are the factors on which number of commands received by
> Miniport
> depends.??
> NOTE: For every command I complete I call next request.I am having a
> SRB
> extension to keep context for every command.
> 3> How are SRBs allocated by port driver?? from which memory pool??
> Does the
> size of SRB Extension has to do something with number of SRBs that port
> driver can allocate.
>
>
> Any help is highly appreciated.
> thanks
> ajitabh
>
> —
> You are currently subscribed to ntdev as: xxxxx@storagecraft.com
> To unsubscribe send a blank email to xxxxx@lists.osr.com
>
> —
> You are currently subscribed to ntdev as: xxxxx@lsil.com
> To unsubscribe send a blank email to xxxxx@lists.osr.com
>
>
>
> —
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></mailto:xxxxx></mailto:xxxxx>

6

And don’t forget MaxScatterGatherList.

–
Gary G. Little
Have Computer, Will Travel …
909-698-3191
909-551-2105
http://www.wd-3.com
“Saxena, Ajitabh Prakash” wrote in message news:xxxxx@ntdev…
hi all,
I am working on a SCSI miniport driver. I am trying to get better performance from my driver and my bottle neck is Number of commands I get from PORT driver.

Questions:-

1> How can I tune my driver to receive more number of commands.???
2> What are the factors on which number of commands received by Miniport depends.??
NOTE: For every command I complete I call next request.I am having a SRB extension to keep context for every command.
3> How are SRBs allocated by port driver?? from which memory pool?? Does the size of SRB Extension has to do something with number of SRBs that port driver can allocate.

Any help is highly appreciated.
thanks
ajitabh

7

Can you please explain further that how does MaxScatterGatherList influence
the number of commands in ScsiMiniport.

-----Original Message-----
From: Gary G. Little [mailto:xxxxx@aerosurf.net]
Sent: Wednesday, March 19, 2003 3:29 PM
To: NT Developers Interest List
Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver

And don’t forget MaxScatterGatherList.

–
Gary G. Little
Have Computer, Will Travel …
909-698-3191
909-551-2105
http://www.wd-3.com http:

“Saxena, Ajitabh Prakash” < xxxxx@lsil.com mailto:xxxxx >
wrote in message news:xxxxx@ntdev news:xxxxx …
hi all,
I am working on a SCSI miniport driver. I am trying to get better
performance from my driver and my bottle neck is Number of commands I get
from PORT driver.

Questions:-

1> How can I tune my driver to receive more number of commands.???
2> What are the factors on which number of commands received by Miniport
depends.??
NOTE: For every command I complete I call next request.I am having a SRB
extension to keep context for every command.
3> How are SRBs allocated by port driver?? from which memory pool?? Does the
size of SRB Extension has to do something with number of SRBs that port
driver can allocate.

Any help is highly appreciated.
thanks
ajitabh

—
You are currently subscribed to ntdev as: xxxxx@lsil.com
To unsubscribe send a blank email to xxxxx@lists.osr.com</news:xxxxx></mailto:xxxxx></http:>

8

MaxScatterGatherList will allow you bigger sized IOs going out on the wire. If it is set to a smaller value, and if the IO has more physically discontinuous chunks that the miniport claims it supports( via SG list), the IO will be broken down internally, resulting in a drop in performance.

m

-----Original Message-----
From: Saxena, Ajitabh Prakash [mailto:xxxxx@lsil.com]
Sent: Wednesday, March 19, 2003 12:32 PM
To: NT Developers Interest List
Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver

Can you please explain further that how does MaxScatterGatherList influence the number of commands in ScsiMiniport.

-----Original Message-----
From: Gary G. Little [mailto:xxxxx@aerosurf.net]
Sent: Wednesday, March 19, 2003 3:29 PM
To: NT Developers Interest List
Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver

And don’t forget MaxScatterGatherList.

–
Gary G. Little
Have Computer, Will Travel …
909-698-3191
909-551-2105
http://www.wd-3.com

“Saxena, Ajitabh Prakash” < xxxxx@lsil.com> wrote in message news:xxxxx@ntdev…
hi all,
I am working on a SCSI miniport driver. I am trying to get better performance from my driver and my bottle neck is Number of commands I get from PORT driver.

Questions:-

1> How can I tune my driver to receive more number of commands.???
2> What are the factors on which number of commands received by Miniport depends.??
NOTE: For every command I complete I call next request.I am having a SRB extension to keep context for every command.
3> How are SRBs allocated by port driver?? from which memory pool?? Does the size of SRB Extension has to do something with number of SRBs that port driver can allocate.

Any help is highly appreciated.
thanks
ajitabh

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9

It is the maximum size in pages for single SCSI transfer.

Max

----- Original Message -----
From: Saxena, Ajitabh Prakash
To: NT Developers Interest List
Sent: Wednesday, March 19, 2003 11:32 PM
Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver

Can you please explain further that how does MaxScatterGatherList influence the number of commands in ScsiMiniport.
-----Original Message-----
From: Gary G. Little [mailto:xxxxx@aerosurf.net]
Sent: Wednesday, March 19, 2003 3:29 PM
To: NT Developers Interest List
Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver

And don’t forget MaxScatterGatherList.

–
Gary G. Little
Have Computer, Will Travel …
909-698-3191
909-551-2105
http://www.wd-3.com
“Saxena, Ajitabh Prakash” wrote in message news:xxxxx@ntdev…
hi all,
I am working on a SCSI miniport driver. I am trying to get better performance from my driver and my bottle neck is Number of commands I get from PORT driver.

Questions:-

1> How can I tune my driver to receive more number of commands.???
2> What are the factors on which number of commands received by Miniport depends.??
NOTE: For every command I complete I call next request.I am having a SRB extension to keep context for every command.
3> How are SRBs allocated by port driver?? from which memory pool?? Does the size of SRB Extension has to do something with number of SRBs that port driver can allocate.

Any help is highly appreciated.
thanks
ajitabh

—
You are currently subscribed to ntdev as: xxxxx@lsil.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
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10

NumberOfRequests relates to number of commands. MaxScatterGatherList can be used to increase the buffer size from 64K up to a maximum of 255 PAGES, or about 1Meg minus one PAGE. That plus multiple commands will dramatically increase SCSI transfer rates.

–
Gary G. Little
Have Computer, Will Travel …
909-698-3191
909-551-2105
http://www.wd-3.com
“Saxena, Ajitabh Prakash” wrote in message news:xxxxx@ntdev…
Can you please explain further that how does MaxScatterGatherList influence the number of commands in ScsiMiniport.
-----Original Message-----
From: Gary G. Little [mailto:xxxxx@aerosurf.net]
Sent: Wednesday, March 19, 2003 3:29 PM
To: NT Developers Interest List
Subject: [ntdev] Re: Number Of commands in SCSI Miniport Driver

And don’t forget MaxScatterGatherList.

–
Gary G. Little
Have Computer, Will Travel …
909-698-3191
909-551-2105
http://www.wd-3.com
“Saxena, Ajitabh Prakash” wrote in message news:xxxxx@ntdev…
hi all,
I am working on a SCSI miniport driver. I am trying to get better performance from my driver and my bottle neck is Number of commands I get from PORT driver.

Questions:-

1> How can I tune my driver to receive more number of commands.???
2> What are the factors on which number of commands received by Miniport depends.??
NOTE: For every command I complete I call next request.I am having a SRB extension to keep context for every command.
3> How are SRBs allocated by port driver?? from which memory pool?? Does the size of SRB Extension has to do something with number of SRBs that port driver can allocate.

Any help is highly appreciated.
thanks
ajitabh

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