Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753807AbbHYCOq (ORCPT ); Mon, 24 Aug 2015 22:14:46 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:20486 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751352AbbHYCOo (ORCPT ); Mon, 24 Aug 2015 22:14:44 -0400 Message-ID: <55DBCF68.9000402@oracle.com> Date: Tue, 25 Aug 2015 10:14:00 +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: Rafal Mielniczuk CC: "axboe@fb.com" , "hch@infradead.org" , "linux-kernel@vger.kernel.org" , "xen-devel@lists.xenproject.org" , "avanzini.arianna@gmail.com" , David Vrabel , "konrad.wilk@oracle.com" , Marcus Granado , Roger Pau Monne Subject: Re: [PATCH v3] xen/blkfront: convert to blk-mq APIs References: <1436781324-28289-1-git-send-email-bob.liu@oracle.com> <55D46468.2080107@oracle.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 15389 Lines: 417 Hi Rafal, Please have a try adding "--iodepth_batch=32 --iodepth_batch_complete=32" to the fio command line. I didn't see this issue any more, neither for domU. Thanks, -Bob On 08/21/2015 04:46 PM, Rafal Mielniczuk wrote: > On 19/08/15 12:12, Bob Liu wrote: >> 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 > > Hello, > > We got a problem with the lack of merges also when we tested on null_blk device in dom0 directly. > When we enabled multi queue block-layer we got no merges, even when we set the number of submission queues to 1. > > If I don't miss anything, that could suggest the problem lays somewhere in the blk-mq layer itself? > > Please take a look at the results below: > > fio --name=test --ioengine=libaio --rw=read --numjobs=8 --iodepth=32 \ > --time_based=1 --runtime=30 --bs=4KB --filename=/dev/nullb0 \ > --direct=1 --group_reporting=1 > > ======================================================================== > modprobe null_blk irqmode=2 completion_nsec=1000000 queue_mode=1 submit_queues=1 > ======================================================================== > READ: io=13692MB, aggrb=467320KB/s, minb=467320KB/s, maxb=467320KB/s, mint=30002msec, maxt=30002msec > > Disk stats (read/write): > nullb0: ios=991026/0, merge=2499524/0, ticks=1846952/0, in_queue=900012, util=100.00% > > ======================================================================== > modprobe null_blk irqmode=2 completion_nsec=1000000 queue_mode=2 submit_queues=1 > ======================================================================== > READ: io=6839.1MB, aggrb=233452KB/s, minb=233452KB/s, maxb=233452KB/s, mint=30002msec, maxt=30002msec > > Disk stats (read/write): > nullb0: ios=1743967/0, merge=0/0, ticks=1712900/0, in_queue=1839072, util=100.00% > > Thanks, > Rafal > >> >> 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/