lkml.org 
[lkml]   [2003]   [Apr]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectClustering of Request in block layer
Hi,

As per my understanding the block layer clusters requests for all
block drivers.
Clustering -
Creating a linked list of buffer_heads using b_reqnext.

But, when I run my block driver and try to view the number of
clustered requests in my Request function, I do not find any
clustering done.

void own_request(request_queue_t *q)
{
struct buffer_head *tmp;
int count;
while(1) {
INIT_REQUEST;
printk("<1>request %p: cmd %i sec %li (nr. %li)\n", CURRENT,
CURRENT->cmd,
CURRENT->sector,
CURRENT->current_nr_sectors);
count=0;
for (tmp=bh; tmp; tmp=tmp->b_reqnext)
count ++;
printk("Count = %d\n", count);
end_request(1); /* success */
}
}

The above always shows 'Count = 1'. dd if=/dev/mydevice of=/dev/null.
Does this mean that no clustering is done ??

Just read a document a "http://www.usenix.org/publications/library/proceedings/usenix2000/freenix/full_papers/gopinath/gopinath_html/node14.html"
which says "This clustering is performed only for the drivers compiled in the kernel and not for loadable modules."

Is this the reason ??

Regards,
Mala

--
__________________________________________________________
Sign-up for your own FREE Personalized E-mail at Mail.com
http://www.mail.com/?sr=signup

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:34    [W:0.029 / U:1.648 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site