Re: CSCAN I/O scheduler for 2.6.10 kernel

["Vishal Patil" <vishpat@gmail.com>]

I am attaching the CSCAN scheduler patch for 2.6.16.2 kernel.

- Vishal

On 4/5/06, Vishal Patil <vishpat@gmail.com> wrote:
> The two queues are used for sorting purposes ONLY. There is the
> dispatch queue to which the requests are moved from one of the queues
> and the request is processes of the dispatch queue.
>
> Example:
>
> Current request  = 40
> Q1 = 55 58 67 72
> Q2 = 10 23 38
>
> Assuming no other request arrives, these will be pushed on the
> dispatch queue in the following order
> 55 58 67 72 10 23 38
>
> I hope this clears things up.
>
> Also I have found that the patch that I had submitted earlier has few
> bugs in it. I am going to fix those and then submit a patch for 2.6.16
> Thanks.
>
>
> - Vishal
>
>
>
> On 4/5/06, Antonio Vargas <windenntw@gmail.com> wrote:
> > On 4/4/06, Vishal Patil <vishpat@gmail.com> wrote:
> > > In that case it would be a normal elevator algorithm and that has a
> > > possiblity of starving the requests at one end of the disk.
> > >
> > > - Vishal
> > >
> > > On 4/4/06, Bill Davidsen <davidsen@tmr.com> wrote:
> > > > Vishal Patil wrote:
> > > > > Maintain two queues which will be sorted in ascending order using Red
> > > > > Black Trees. When a disk request arrives and if the block number it
> > > > > refers to is greater than the block number of the current request
> > > > > being served add (merge) it to the first sorted queue or else add
> > > > > (merge) it to the second sorted queue. Keep on servicing the requests
> > > > > from the first request queue until it is empty after which switch over
> > > > > to the second queue and now reverse the roles of the two queues.
> > > > > Simple and Sweet. Many thanks for the awesome block I/O layer in the
> > > > > 2.6 kernel.
> > > > >
> > > > Why both queues sorting in ascending order? I would think that one
> > > > should be in descending order, which would reduce the seek distance
> > > > between the last i/o on one queue and the first on the next.
> > > >
> >
> > But, if there are two queues, one which is being processed and other
> > which gets the new requests (and the corresponding queue switch when
> > the current is empty), then there is no way to get starved when they
> > are sorted in opposite order.
> >
> >
> > --
> > Greetz, Antonio Vargas aka winden of network
> >
> > http://wind.codepixel.com/
> > windNOenSPAMntw@gmail.com
> > thesameasabove@amigascne.org
> >
> > Every day, every year
> > you have to work
> > you have to study
> > you have to scene.
> >
>
>
> --
> Every passing minute is another chance to turn it all around.
>


--
Every passing minute is another chance to turn it all around.

Attachment: cscan-2.6.16.2-patch
Description: Binary data