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SubjectRe: queue_nr_requests needs to be selective


Andrew,

I will merge and test this patch tonight. Yes, this makes much more
sense.

:-)

Jeff

On Fri, Mar 01, 2002 at 07:50:08PM -0800, Andrew Morton wrote:
> "Jeff V. Merkey" wrote:
> >
> > Andrew,
> >
> > Patch tested and stable. I has to manually modify the value
> > in /usr/src/linux/include/linux/blkdev.h from 128 to 1024
> > since I noticed the 3Ware driver is going through the scsi.c
> > call to blk_init_queue() macro in this include file. I am
> > assuming that at some point, Adam and the other folks will
> > call this api directly.
> >
> > Performance increased 2-3 % to 319 MB/S on dual 33/66 buses,
> > and utilization dropped to 27% +-. All of this activity is
> > DMA based and copyless between reading/writing nodes and
> > I am running this UP and getting these numbers. I ran SMP
> > as well and it also looks good.
> >
> > Someone needs to look at just how the drivers will call
> > __blk_init_queue() directly to setup custom depth queues
> > from scsi.c since this call is originating there for
> > those IDE RAID drivers that fake out the system in thinking
> > they are SCSI.
> >
>
> So it would be more straightforward to just allow the queue
> to be grown later on?
>
>
>
> --- 2.4.19-pre2/drivers/block/ll_rw_blk.c~blk-queue Fri Mar 1 19:40:12 2002
> +++ 2.4.19-pre2-akpm/drivers/block/ll_rw_blk.c Fri Mar 1 19:48:33 2002
> @@ -117,16 +117,6 @@ int * max_readahead[MAX_BLKDEV];
> */
> int * max_sectors[MAX_BLKDEV];
>
> -/*
> - * The total number of requests in each queue.
> - */
> -static int queue_nr_requests;
> -
> -/*
> - * The threshold around which we make wakeup decisions
> - */
> -static int batch_requests;
> -
> static inline int get_max_sectors(kdev_t dev)
> {
> if (!max_sectors[MAJOR(dev)])
> @@ -180,7 +170,7 @@ static int __blk_cleanup_queue(struct re
> **/
> void blk_cleanup_queue(request_queue_t * q)
> {
> - int count = queue_nr_requests;
> + int count = q->nr_requests;
>
> count -= __blk_cleanup_queue(&q->rq[READ]);
> count -= __blk_cleanup_queue(&q->rq[WRITE]);
> @@ -330,31 +320,62 @@ void generic_unplug_device(void *data)
> spin_unlock_irqrestore(&io_request_lock, flags);
> }
>
> +/** blk_grow_request_list
> + * @q: The &request_queue_t
> + * @nr_requests: how many requests are desired
> + *
> + * More free requests are added to the queue's free lists, bringing
> + * the total number of requests to @nr_requests.
> + *
> + * The requests are added equally to the request queue's read
> + * and write freelists.
> + *
> + * This function can sleep.
> + *
> + * Returns the (new) number of requests which the queue has available.
> + */
> +int blk_grow_request_list(request_queue_t *q, int nr_requests)
> +{
> + spin_lock_irq(&io_request_lock);
> + while (q->nr_requests < nr_requests) {
> + struct request *rq;
> + int rw;
> +
> + spin_unlock_irq(&io_request_lock);
> + rq = kmem_cache_alloc(request_cachep, SLAB_KERNEL);
> + spin_lock_irq(&io_request_lock);
> + if (rq == NULL)
> + break;
> + memset(rq, 0, sizeof(*rq));
> + rq->rq_status = RQ_INACTIVE;
> + rw = q->nr_requests & 1;
> + list_add(&rq->queue, &q->rq[rw].free);
> + q->rq[rw].count++;
> + q->nr_requests++;
> + }
> + q->batch_requests = q->nr_requests / 4;
> + spin_unlock_irq(&io_request_lock);
> + return q->nr_requests;
> +}
> +
> static void blk_init_free_list(request_queue_t *q)
> {
> - struct request *rq;
> - int i;
> + struct sysinfo si;
> + int megs; /* Total memory, in megabytes */
> + int nr_requests;
>
> INIT_LIST_HEAD(&q->rq[READ].free);
> INIT_LIST_HEAD(&q->rq[WRITE].free);
> q->rq[READ].count = 0;
> q->rq[WRITE].count = 0;
> + q->nr_requests = 0;
>
> - /*
> - * Divide requests in half between read and write
> - */
> - for (i = 0; i < queue_nr_requests; i++) {
> - rq = kmem_cache_alloc(request_cachep, SLAB_KERNEL);
> - if (rq == NULL) {
> - /* We'll get a `leaked requests' message from blk_cleanup_queue */
> - printk(KERN_EMERG "blk_init_free_list: error allocating requests\n");
> - break;
> - }
> - memset(rq, 0, sizeof(struct request));
> - rq->rq_status = RQ_INACTIVE;
> - list_add(&rq->queue, &q->rq[i&1].free);
> - q->rq[i&1].count++;
> - }
> + si_meminfo(&si);
> + megs = si.totalram >> (20 - PAGE_SHIFT);
> + nr_requests = 128;
> + if (megs < 32)
> + nr_requests /= 2;
> + blk_grow_request_list(q, nr_requests);
>
> init_waitqueue_head(&q->wait_for_requests[0]);
> init_waitqueue_head(&q->wait_for_requests[1]);
> @@ -610,7 +631,7 @@ void blkdev_release_request(struct reque
> */
> if (q) {
> list_add(&req->queue, &q->rq[rw].free);
> - if (++q->rq[rw].count >= batch_requests &&
> + if (++q->rq[rw].count >= q->batch_requests &&
> waitqueue_active(&q->wait_for_requests[rw]))
> wake_up(&q->wait_for_requests[rw]);
> }
> @@ -802,7 +823,7 @@ get_rq:
> * See description above __get_request_wait()
> */
> if (rw_ahead) {
> - if (q->rq[rw].count < batch_requests) {
> + if (q->rq[rw].count < q->batch_requests) {
> spin_unlock_irq(&io_request_lock);
> goto end_io;
> }
> @@ -1149,12 +1170,9 @@ void end_that_request_last(struct reques
> blkdev_release_request(req);
> }
>
> -#define MB(kb) ((kb) << 10)
> -
> int __init blk_dev_init(void)
> {
> struct blk_dev_struct *dev;
> - int total_ram;
>
> request_cachep = kmem_cache_create("blkdev_requests",
> sizeof(struct request),
> @@ -1170,22 +1188,6 @@ int __init blk_dev_init(void)
> memset(max_readahead, 0, sizeof(max_readahead));
> memset(max_sectors, 0, sizeof(max_sectors));
>
> - total_ram = nr_free_pages() << (PAGE_SHIFT - 10);
> -
> - /*
> - * Free request slots per queue.
> - * (Half for reads, half for writes)
> - */
> - queue_nr_requests = 64;
> - if (total_ram > MB(32))
> - queue_nr_requests = 128;
> -
> - /*
> - * Batch frees according to queue length
> - */
> - batch_requests = queue_nr_requests/4;
> - printk("block: %d slots per queue, batch=%d\n", queue_nr_requests, batch_requests);
> -
> #ifdef CONFIG_AMIGA_Z2RAM
> z2_init();
> #endif
> @@ -1296,6 +1298,7 @@ int __init blk_dev_init(void)
> EXPORT_SYMBOL(io_request_lock);
> EXPORT_SYMBOL(end_that_request_first);
> EXPORT_SYMBOL(end_that_request_last);
> +EXPORT_SYMBOL(blk_grow_request_list);
> EXPORT_SYMBOL(blk_init_queue);
> EXPORT_SYMBOL(blk_get_queue);
> EXPORT_SYMBOL(blk_cleanup_queue);
> --- 2.4.19-pre2/include/linux/blkdev.h~blk-queue Fri Mar 1 19:40:12 2002
> +++ 2.4.19-pre2-akpm/include/linux/blkdev.h Fri Mar 1 19:40:12 2002
> @@ -79,6 +79,16 @@ struct request_queue
> struct request_list rq[2];
>
> /*
> + * The total number of requests on each queue
> + */
> + int nr_requests;
> +
> + /*
> + * Batching threshold for sleep/wakeup decisions
> + */
> + int batch_requests;
> +
> + /*
> * Together with queue_head for cacheline sharing
> */
> struct list_head queue_head;
> @@ -157,6 +167,7 @@ extern void blkdev_release_request(struc
> /*
> * Access functions for manipulating queue properties
> */
> +extern int blk_grow_request_list(request_queue_t *q, int nr_requests);
> extern void blk_init_queue(request_queue_t *, request_fn_proc *);
> extern void blk_cleanup_queue(request_queue_t *);
> extern void blk_queue_headactive(request_queue_t *, int);
-
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