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 [off-list ref] wrote:

On Fri, May 27, 2011 at 8:29 AM, mani [off-list ref] wrote:

quoted

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)

quoted

{
        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 ?

quoted

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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