On Sun, Apr 13 2003, Nirmala S wrote:
> 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 ??
try to add a bs=256k or something like that.
> 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."
2.2 and newer clusters for all drivers.
-- Jens Axboe- 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/
This archive was generated by hypermail 2b29 : Tue Apr 15 2003 - 22:00:28 EST