Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753812AbbHSLMR (ORCPT ); Wed, 19 Aug 2015 07:12:17 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:34285 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753739AbbHSLMO (ORCPT ); Wed, 19 Aug 2015 07:12:14 -0400 Message-ID: <55D46468.2080107@oracle.com> Date: Wed, 19 Aug 2015 19:11:36 +0800 From: Bob Liu User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: axboe@fb.com, hch@infradead.org CC: linux-kernel@vger.kernel.org, Rafal Mielniczuk , xen-devel@lists.xenproject.org, avanzini.arianna@gmail.com, david.vrabel@citrix.com, konrad.wilk@oracle.com, marcus.granado@citrix.com, roger.pau@citrix.com Subject: Re: [PATCH v3] xen/blkfront: convert to blk-mq APIs References: <1436781324-28289-1-git-send-email-bob.liu@oracle.com> In-Reply-To: <1436781324-28289-1-git-send-email-bob.liu@oracle.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 12848 Lines: 374 Hi Jens & Christoph, Rafal reported an issue about this patch, that's after this patch no more merges happen and the performance dropped if "modprobe null_blk irqmode=2 completion_nsec=1000000", but works fine if "modprobe null_blk". I'm not sure whether it's as expect or not. Do you have any suggestions? Thank you! Here is the test result: fio --name=test --ioengine=libaio --rw=read --numjobs=8 --iodepth=32 \ --time_based=1 --runtime=30 --bs=4KB --filename=/dev/xvdb \ --direct=1 --group_reporting=1 --iodepth_batch=16 ======================================================================== modprobe null_blk ======================================================================== ------------------------------------------------------------------------ *no patch* (avgrq-sz = 8.00 avgqu-sz=5.00) ------------------------------------------------------------------------ READ: io=10655MB, aggrb=363694KB/s, minb=363694KB/s, maxb=363694KB/s, mint=30001msec, maxt=30001msec Disk stats (read/write): xvdb: ios=2715852/0, merge=1089/0, ticks=126572/0, in_queue=127456, util=100.00% ------------------------------------------------------------------------ *with patch* (avgrq-sz = 8.00 avgqu-sz=8.00) ------------------------------------------------------------------------ READ: io=20655MB, aggrb=705010KB/s, minb=705010KB/s, maxb=705010KB/s, mint=30001msec, maxt=30001msec Disk stats (read/write): xvdb: ios=5274633/0, merge=22/0, ticks=243208/0, in_queue=242908, util=99.98% ======================================================================== modprobe null_blk irqmode=2 completion_nsec=1000000 ======================================================================== ------------------------------------------------------------------------ *no patch* (avgrq-sz = 34.00 avgqu-sz=38.00) ------------------------------------------------------------------------ READ: io=10372MB, aggrb=354008KB/s, minb=354008KB/s, maxb=354008KB/s, mint=30003msec, maxt=30003msec Disk stats (read/write): xvdb: ios=621760/0, *merge=1988170/0*, ticks=1136700/0, in_queue=1146020, util=99.76% ------------------------------------------------------------------------ *with patch* (avgrq-sz = 8.00 avgqu-sz=28.00) ------------------------------------------------------------------------ READ: io=2876.8MB, aggrb=98187KB/s, minb=98187KB/s, maxb=98187KB/s, mint=30002msec, maxt=30002msec Disk stats (read/write): xvdb: ios=734048/0, merge=0/0, ticks=843584/0, in_queue=843080, util=99.72% Regards, -Bob On 07/13/2015 05:55 PM, Bob Liu wrote: > Note: This patch is based on original work of Arianna's internship for > GNOME's Outreach Program for Women. > > Only one hardware queue is used now, so there is no performance change. > > The legacy non-mq code is deleted completely which is the same as other > drivers like virtio, mtip, and nvme. > > Also dropped one unnecessary holding of info->io_lock when calling > blk_mq_stop_hw_queues(). > > Changes in v2: > - Reorganized blk_mq_queue_rq() > - Restored most io_locks in place > > Change in v3: > - Rename blk_mq_queue_rq to blkif_queue_rq > > Signed-off-by: Arianna Avanzini > Signed-off-by: Bob Liu > Reviewed-by: Christoph Hellwig > Acked-by: Jens Axboe > --- > drivers/block/xen-blkfront.c | 146 +++++++++++++++++------------------------- > 1 file changed, 60 insertions(+), 86 deletions(-) > > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > index 6d89ed3..5b45ee5 100644 > --- a/drivers/block/xen-blkfront.c > +++ b/drivers/block/xen-blkfront.c > @@ -37,6 +37,7 @@ > > #include > #include > +#include > #include > #include > #include > @@ -148,6 +149,7 @@ struct blkfront_info > unsigned int feature_persistent:1; > unsigned int max_indirect_segments; > int is_ready; > + struct blk_mq_tag_set tag_set; > }; > > static unsigned int nr_minors; > @@ -616,54 +618,41 @@ static inline bool blkif_request_flush_invalid(struct request *req, > !(info->feature_flush & REQ_FUA))); > } > > -/* > - * do_blkif_request > - * read a block; request is in a request queue > - */ > -static void do_blkif_request(struct request_queue *rq) > +static int blkif_queue_rq(struct blk_mq_hw_ctx *hctx, > + const struct blk_mq_queue_data *qd) > { > - struct blkfront_info *info = NULL; > - struct request *req; > - int queued; > - > - pr_debug("Entered do_blkif_request\n"); > - > - queued = 0; > + struct blkfront_info *info = qd->rq->rq_disk->private_data; > > - while ((req = blk_peek_request(rq)) != NULL) { > - info = req->rq_disk->private_data; > - > - if (RING_FULL(&info->ring)) > - goto wait; > + blk_mq_start_request(qd->rq); > + spin_lock_irq(&info->io_lock); > + if (RING_FULL(&info->ring)) > + goto out_busy; > > - blk_start_request(req); > + if (blkif_request_flush_invalid(qd->rq, info)) > + goto out_err; > > - if (blkif_request_flush_invalid(req, info)) { > - __blk_end_request_all(req, -EOPNOTSUPP); > - continue; > - } > + if (blkif_queue_request(qd->rq)) > + goto out_busy; > > - pr_debug("do_blk_req %p: cmd %p, sec %lx, " > - "(%u/%u) [%s]\n", > - req, req->cmd, (unsigned long)blk_rq_pos(req), > - blk_rq_cur_sectors(req), blk_rq_sectors(req), > - rq_data_dir(req) ? "write" : "read"); > - > - if (blkif_queue_request(req)) { > - blk_requeue_request(rq, req); > -wait: > - /* Avoid pointless unplugs. */ > - blk_stop_queue(rq); > - break; > - } > + flush_requests(info); > + spin_unlock_irq(&info->io_lock); > + return BLK_MQ_RQ_QUEUE_OK; > > - queued++; > - } > +out_err: > + spin_unlock_irq(&info->io_lock); > + return BLK_MQ_RQ_QUEUE_ERROR; > > - if (queued != 0) > - flush_requests(info); > +out_busy: > + spin_unlock_irq(&info->io_lock); > + blk_mq_stop_hw_queue(hctx); > + return BLK_MQ_RQ_QUEUE_BUSY; > } > > +static struct blk_mq_ops blkfront_mq_ops = { > + .queue_rq = blkif_queue_rq, > + .map_queue = blk_mq_map_queue, > +}; > + > static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size, > unsigned int physical_sector_size, > unsigned int segments) > @@ -671,9 +660,22 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size, > struct request_queue *rq; > struct blkfront_info *info = gd->private_data; > > - rq = blk_init_queue(do_blkif_request, &info->io_lock); > - if (rq == NULL) > + memset(&info->tag_set, 0, sizeof(info->tag_set)); > + info->tag_set.ops = &blkfront_mq_ops; > + info->tag_set.nr_hw_queues = 1; > + info->tag_set.queue_depth = BLK_RING_SIZE(info); > + info->tag_set.numa_node = NUMA_NO_NODE; > + info->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE; > + info->tag_set.cmd_size = 0; > + info->tag_set.driver_data = info; > + > + if (blk_mq_alloc_tag_set(&info->tag_set)) > return -1; > + rq = blk_mq_init_queue(&info->tag_set); > + if (IS_ERR(rq)) { > + blk_mq_free_tag_set(&info->tag_set); > + return -1; > + } > > queue_flag_set_unlocked(QUEUE_FLAG_VIRT, rq); > > @@ -901,19 +903,15 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity, > static void xlvbd_release_gendisk(struct blkfront_info *info) > { > unsigned int minor, nr_minors; > - unsigned long flags; > > if (info->rq == NULL) > return; > > - spin_lock_irqsave(&info->io_lock, flags); > - > /* No more blkif_request(). */ > - blk_stop_queue(info->rq); > + blk_mq_stop_hw_queues(info->rq); > > /* No more gnttab callback work. */ > gnttab_cancel_free_callback(&info->callback); > - spin_unlock_irqrestore(&info->io_lock, flags); > > /* Flush gnttab callback work. Must be done with no locks held. */ > flush_work(&info->work); > @@ -925,20 +923,18 @@ static void xlvbd_release_gendisk(struct blkfront_info *info) > xlbd_release_minors(minor, nr_minors); > > blk_cleanup_queue(info->rq); > + blk_mq_free_tag_set(&info->tag_set); > info->rq = NULL; > > put_disk(info->gd); > info->gd = NULL; > } > > +/* Must be called with io_lock holded */ > static void kick_pending_request_queues(struct blkfront_info *info) > { > - if (!RING_FULL(&info->ring)) { > - /* Re-enable calldowns. */ > - blk_start_queue(info->rq); > - /* Kick things off immediately. */ > - do_blkif_request(info->rq); > - } > + if (!RING_FULL(&info->ring)) > + blk_mq_start_stopped_hw_queues(info->rq, true); > } > > static void blkif_restart_queue(struct work_struct *work) > @@ -963,7 +959,7 @@ static void blkif_free(struct blkfront_info *info, int suspend) > BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED; > /* No more blkif_request(). */ > if (info->rq) > - blk_stop_queue(info->rq); > + blk_mq_stop_hw_queues(info->rq); > > /* Remove all persistent grants */ > if (!list_empty(&info->grants)) { > @@ -1144,7 +1140,6 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) > RING_IDX i, rp; > unsigned long flags; > struct blkfront_info *info = (struct blkfront_info *)dev_id; > - int error; > > spin_lock_irqsave(&info->io_lock, flags); > > @@ -1185,37 +1180,37 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) > continue; > } > > - error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO; > + req->errors = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO; > switch (bret->operation) { > case BLKIF_OP_DISCARD: > if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) { > struct request_queue *rq = info->rq; > printk(KERN_WARNING "blkfront: %s: %s op failed\n", > info->gd->disk_name, op_name(bret->operation)); > - error = -EOPNOTSUPP; > + req->errors = -EOPNOTSUPP; > info->feature_discard = 0; > info->feature_secdiscard = 0; > queue_flag_clear(QUEUE_FLAG_DISCARD, rq); > queue_flag_clear(QUEUE_FLAG_SECDISCARD, rq); > } > - __blk_end_request_all(req, error); > + blk_mq_complete_request(req); > break; > case BLKIF_OP_FLUSH_DISKCACHE: > case BLKIF_OP_WRITE_BARRIER: > if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) { > printk(KERN_WARNING "blkfront: %s: %s op failed\n", > info->gd->disk_name, op_name(bret->operation)); > - error = -EOPNOTSUPP; > + req->errors = -EOPNOTSUPP; > } > if (unlikely(bret->status == BLKIF_RSP_ERROR && > info->shadow[id].req.u.rw.nr_segments == 0)) { > printk(KERN_WARNING "blkfront: %s: empty %s op failed\n", > info->gd->disk_name, op_name(bret->operation)); > - error = -EOPNOTSUPP; > + req->errors = -EOPNOTSUPP; > } > - if (unlikely(error)) { > - if (error == -EOPNOTSUPP) > - error = 0; > + if (unlikely(req->errors)) { > + if (req->errors == -EOPNOTSUPP) > + req->errors = 0; > info->feature_flush = 0; > xlvbd_flush(info); > } > @@ -1226,7 +1221,7 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) > dev_dbg(&info->xbdev->dev, "Bad return from blkdev data " > "request: %x\n", bret->status); > > - __blk_end_request_all(req, error); > + blk_mq_complete_request(req); > break; > default: > BUG(); > @@ -1555,28 +1550,6 @@ static int blkif_recover(struct blkfront_info *info) > > kfree(copy); > > - /* > - * Empty the queue, this is important because we might have > - * requests in the queue with more segments than what we > - * can handle now. > - */ > - spin_lock_irq(&info->io_lock); > - while ((req = blk_fetch_request(info->rq)) != NULL) { > - if (req->cmd_flags & > - (REQ_FLUSH | REQ_FUA | REQ_DISCARD | REQ_SECURE)) { > - list_add(&req->queuelist, &requests); > - continue; > - } > - merge_bio.head = req->bio; > - merge_bio.tail = req->biotail; > - bio_list_merge(&bio_list, &merge_bio); > - req->bio = NULL; > - if (req->cmd_flags & (REQ_FLUSH | REQ_FUA)) > - pr_alert("diskcache flush request found!\n"); > - __blk_end_request_all(req, 0); > - } > - spin_unlock_irq(&info->io_lock); > - > xenbus_switch_state(info->xbdev, XenbusStateConnected); > > spin_lock_irq(&info->io_lock); > @@ -1591,9 +1564,10 @@ static int blkif_recover(struct blkfront_info *info) > /* Requeue pending requests (flush or discard) */ > list_del_init(&req->queuelist); > BUG_ON(req->nr_phys_segments > segs); > - blk_requeue_request(info->rq, req); > + blk_mq_requeue_request(req); > } > spin_unlock_irq(&info->io_lock); > + blk_mq_kick_requeue_list(info->rq); > > while ((bio = bio_list_pop(&bio_list)) != NULL) { > /* Traverse the list of pending bios and re-queue them */ > -- 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/