Re: Changes in block layer for IOScheduler Insertion selection

[Matthias Brugger <matthias.bgg@xxxxxxxxxxxxxx>]

On 06/02/2011 05:41 AM, mani wrote:

Dear All,

Any suggestions on the below point ?

have you tried different benchmarks?
This can give you an idea of the impact. It seems that up to now, you've only executed sequential read and write access by one process.

Personally I use the fio benchmark. For flash file systems, David Wagner from Free Electrons developed a benchmarksuite. Maybe it would be worse having a look on it.

Best regards,
Matthias Brugger

Thanks in advance..

On Mon, May 30, 2011 at 10:53 AM, mani <manishrma@xxxxxxxxx> wrote:

Dear Eduardo,

   I am using squashfs filesystem. So i am more concern with the read speed.
    whereas below are the details
                                                     read speed   write speed
    ELEVATOR_INSERT_SORT       8 MBps            5MBps
    ELEVATOR_INSERT_BACK      10 MBps           7.2MBps

   used the following command for measurement for both the cases.
   reading
   hdparm -t /dev/mtdblock3
  
   writing
   dd if=/dev/zero of=/dev/mtd3 bs=4096 count=100k

   As of now everything is working fine with those changes
   but i am worried if these changes would have any adverse effect anywhere ?
 
   Thanks.

 

On Fri, May 27, 2011 at 8:37 PM, Eduardo Silva <edsiper@xxxxxxxxx> wrote:

On Fri, May 27, 2011 at 8:29 AM, mani <manishrma@xxxxxxxxx> wrote:
>
> Dear All,
>
> I am working on linux kernel 2.6.32.9 tegra NVIDIA board.
>
> I am getting ~8MBps speed of the Nand disk if i use hdparm
> hdparm -t /dev/mtdblock3
>
> i made changes in block layer of kernel as below:-
>
> block/blk-core.c
> static inline void add_request(struct request_queue *q, struct request *req)
> {
>         drive_stat_acct(req, 1);
>
>         /*
>          * elevator indicated where it wants this request to be
>          * inserted at elevator_merge time
>          */
>
>         __elv_add_request(q, req, ELEVATOR_INSERT_BACK, 0);
>         //__elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
> }
>
>

What are the results for read and write for both cases ?

> changed ELEVATOR_INSERT_SORT to ELEVATOR_INSERT_BACK
> it improves my NAND speed to 10MBps.
>
> I am using "noop" I/O scheduler.
>
> Will this change have any adverse effect in kernel ? or any other side
> effect as far as i am using only Nand no Hard disk.
>
>
> Thanks
> Mani
>
>

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>



--
Eduardo Silva
http://edsiper.linuxchile.cl
http://www.monkey-project.com

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