RE: SPAM-LOW: Re: Disk I/O priority

Don’t forget that some devices do better when they know the full set of
active IRPs, because they can re-order them. I believe even some disk
hardware controllers will reorder requests to reduce seek time. So you may
even be slowing down the total throughput, without benefiting the
“privileged” apps at all.

– arlie

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Eric Thiebaut-George
Sent: Wednesday, August 17, 2005 8:41 AM
To: Windows File Systems Devs Interest List
Subject: SPAM-LOW: Re: [ntfsd] Disk I/O priority

> Depending on the PID which generated the original request, I have to
> decide which request should go straight to the underlying driver,
> and which request should be delayed.

Well, that was exactly, what we were trying out, the *priviledged*
application got more IRPs through us, than the non priviledged ones.
How do you decide the threshold? The ratio of priviledged IRPs to non
proviledged ones. Also, blocking certain IRPs or delaying them makes
the syustem unstable. You will also have to take care of IRPs getting
cancelled because they got delayed (I am sure, with your experience
you know all this).

We haven’t completely figured out the algorithm yet, but at this stage it’s
more of a proof of concept…

Well, process specific information is stripped down at FS leve. There
might be a crooked way though, I am not aware of it. Writing a two
stage driver, attaching one at the FS level that passes the driver
attached to the disk the correct PIDs as IOCTLs…may be might work,
not sure.

That was pretty much what I was thinking. It does look messy but it might be
a candidate if there is no other way…

Eric


Questions? First check the IFS FAQ at
https://www.osronline.com/article.cfm?id=17

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Yes, I’m aware of that. It’s the case for some SATA drives in
particular.

Eric

On Wed, 17 Aug 2005 10:52:21 -0400, “Arlie Davis”
said:
> Don’t forget that some devices do better when they know the full set of
> active IRPs, because they can re-order them. I believe even some disk
> hardware controllers will reorder requests to reduce seek time. So you
> may
> even be slowing down the total throughput, without benefiting the
> “privileged” apps at all.
>
> – arlie
>
>
> -----Original Message-----
> From: xxxxx@lists.osr.com
> [mailto:xxxxx@lists.osr.com] On Behalf Of Eric
> Thiebaut-George
> Sent: Wednesday, August 17, 2005 8:41 AM
> To: Windows File Systems Devs Interest List
> Subject: SPAM-LOW: Re: [ntfsd] Disk I/O priority
>
> > > Depending on the PID which generated the original request, I have to
> > > decide which request should go straight to the underlying driver,
> > > and which request should be delayed.
> >
> > Well, that was exactly, what we were trying out, the priviledged
> > application got more IRPs through us, than the non priviledged ones.
> > How do you decide the threshold? The ratio of priviledged IRPs to non
> > proviledged ones. Also, blocking certain IRPs or delaying them makes
> > the syustem unstable. You will also have to take care of IRPs getting
> > cancelled because they got delayed (I am sure, with your experience
> > you know all this).
>
> We haven’t completely figured out the algorithm yet, but at this stage
> it’s
> more of a proof of concept…
>
> > Well, process specific information is stripped down at FS leve. There
> > might be a crooked way though, I am not aware of it. Writing a two
> > stage driver, attaching one at the FS level that passes the driver
> > attached to the disk the correct PIDs as IOCTLs…may be might work,
> > not sure.
>
> That was pretty much what I was thinking. It does look messy but it might
> be
> a candidate if there is no other way…
>
> Eric
>
> —
> Questions? First check the IFS FAQ at
> https://www.osronline.com/article.cfm?id=17
>
> You are currently subscribed to ntfsd as: xxxxx@stonestreetone.com To
> unsubscribe send a blank email to xxxxx@lists.osr.com
>
>
>
>
> —
> Questions? First check the IFS FAQ at
> https://www.osronline.com/article.cfm?id=17
>
> You are currently subscribed to ntfsd as: xxxxx@dungorm.co.uk
> To unsubscribe send a blank email to xxxxx@lists.osr.com