LookAsideLists

NTDEV
1

Hi all,

I’ve changed my driver towards using LookAsideLists, and now
I’m wondering if for “important” allocations I should preallocate
a spare list in case the LookAsideList resources are down ?
In other words, is there a inbuilt fallback mechanism with
LookAsideLists, or do I still have to provide queueing a request,
or try again with ExAllocate etc. ?

Kind Regards
Else

2

No point in ‘trying again with ExAllocate’ as the lookaside list will
use ExAllocate if there aren’t any available entries on the list. You
can just as well ‘try again with your lookasidelist’. You do have to
deal with the case where there simply aren’t any buffer resources. This
is generally pretty tough to deal with. Mostly drivers tend to error
out, regardless of the consequences. You can reserve a last resort
buffer, but then you have to special case code all over the place to
deal with it. Ugh. Good luck!

=====================
Mark Roddy

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Else Kluger
Sent: Wednesday, May 25, 2005 11:41 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] LookAsideLists

Hi all,

I’ve changed my driver towards using LookAsideLists, and now I’m
wondering if for “important” allocations I should preallocate a spare
list in case the LookAsideList resources are down ?
In other words, is there a inbuilt fallback mechanism with
LookAsideLists, or do I still have to provide queueing a request, or
try again with ExAllocate etc. ?

Kind Regards
Else

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

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

3

LookAside lists can get exhausted. You’ll still need to manage such
fallback resources on your own if you need them.

-p

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Else Kluger
Sent: Wednesday, May 25, 2005 8:41 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] LookAsideLists

Hi all,

I’ve changed my driver towards using LookAsideLists, and now
I’m wondering if for “important” allocations I should
preallocate a spare list in case the LookAsideList resources
are down ?
In other words, is there a inbuilt fallback mechanism with
LookAsideLists, or do I still have to provide queueing a
request, or try again with ExAllocate etc. ?

Kind Regards
Else

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

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

4

Yes. ExAllocate is auto-fallback.

Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
xxxxx@storagecraft.com
http://www.storagecraft.com

----- Original Message -----
From: “Else Kluger”
To: “Windows System Software Devs Interest List”
Sent: Wednesday, May 25, 2005 7:40 PM
Subject: [ntdev] LookAsideLists

> Hi all,
>
> I’ve changed my driver towards using LookAsideLists, and now
> I’m wondering if for “important” allocations I should preallocate
> a spare list in case the LookAsideList resources are down ?
> In other words, is there a inbuilt fallback mechanism with
> LookAsideLists, or do I still have to provide queueing a request,
> or try again with ExAllocate etc. ?
>
> Kind Regards
> Else
>
>
> —
> Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
>
> You are currently subscribed to ntdev as: xxxxx@storagecraft.com
> To unsubscribe send a blank email to xxxxx@lists.osr.com

5

You can specify a function to be called when the look aside list has been
depleted. By default this call is ExAllocatePool() but you can specify your
own call here, thus if you pre-allocate a ‘spare’ list, you can return a
piece of this from the depletion routine.

Look at the second parameter to ExInitializexxxLookasideList().

Pete

Kernel Drivers
Windows Filesystem and Device Driver Consulting
www.KernelDrivers.com
(303)546-0300

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Else Kluger
Sent: Wednesday, May 25, 2005 9:41 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] LookAsideLists

Hi all,

I’ve changed my driver towards using LookAsideLists, and now
I’m wondering if for “important” allocations I should preallocate
a spare list in case the LookAsideList resources are down ?
In other words, is there a inbuilt fallback mechanism with
LookAsideLists, or do I still have to provide queueing a request,
or try again with ExAllocate etc. ?

Kind Regards
Else

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

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

6

I looked at that approach for a driver that does a lot of allocations
and rejected it as not really solving the problem while increasing the
complexity. What happens when the lookaside-lookaside fails? Which list
do you use for ExFreeToxxxx?

=====================
Mark Roddy

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Peter Scott
Sent: Wednesday, May 25, 2005 10:53 AM
To: Windows System Software Devs Interest List
Subject: RE: [ntdev] LookAsideLists

You can specify a function to be called when the look aside list has
been depleted. By default this call is ExAllocatePool() but you can
specify your own call here, thus if you pre-allocate a ‘spare’ list, you
can return a piece of this from the depletion routine.

Look at the second parameter to ExInitializexxxLookasideList().

Pete

Kernel Drivers
Windows Filesystem and Device Driver Consulting www.KernelDrivers.com
(303)546-0300

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Else Kluger
Sent: Wednesday, May 25, 2005 9:41 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] LookAsideLists

Hi all,

I’ve changed my driver towards using LookAsideLists, and now I’m
wondering if for “important” allocations I should preallocate a spare
list in case the LookAsideList resources are down ?
In other words, is there a inbuilt fallback mechanism with
LookAsideLists, or do I still have to provide queueing a request, or
try again with ExAllocate etc. ?

Kind Regards
Else

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

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

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

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

7

Mark,

No doubt this is the situation in any fall-back scenario like this. Limiting
the use of the fall back algorithm to only system critical cases such as
paging paths would reduce the chances but you are still faced with the same
problem in the end.

Pete

Kernel Drivers
Windows Filesystem and Device Driver Consulting
www.KernelDrivers.com
(303)546-0300

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Roddy, Mark
Sent: Wednesday, May 25, 2005 11:48 AM
To: Windows System Software Devs Interest List
Subject: RE: [ntdev] LookAsideLists

I looked at that approach for a driver that does a lot of allocations
and rejected it as not really solving the problem while increasing the
complexity. What happens when the lookaside-lookaside fails? Which list
do you use for ExFreeToxxxx?

=====================
Mark Roddy

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Peter Scott
Sent: Wednesday, May 25, 2005 10:53 AM
To: Windows System Software Devs Interest List
Subject: RE: [ntdev] LookAsideLists

You can specify a function to be called when the look aside list has
been depleted. By default this call is ExAllocatePool() but you can
specify your own call here, thus if you pre-allocate a ‘spare’ list, you
can return a piece of this from the depletion routine.

Look at the second parameter to ExInitializexxxLookasideList().

Pete

Kernel Drivers
Windows Filesystem and Device Driver Consulting www.KernelDrivers.com
(303)546-0300

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Else Kluger
Sent: Wednesday, May 25, 2005 9:41 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] LookAsideLists

Hi all,

I’ve changed my driver towards using LookAsideLists, and now I’m
wondering if for “important” allocations I should preallocate a spare
list in case the LookAsideList resources are down ?
In other words, is there a inbuilt fallback mechanism with
LookAsideLists, or do I still have to provide queueing a request, or
try again with ExAllocate etc. ?

Kind Regards
Else

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

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

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

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

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

You are currently subscribed to ntdev as: unknown lmsubst tag argument: ‘’
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