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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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