Messages in this thread Patch in this message | | | Date | Fri, 01 Mar 2002 19:50:08 -0800 | From | Andrew Morton <> | Subject | Re: queue_nr_requests needs to be selective |
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"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); - 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/
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