block/rnbd: Remove all likely and unlikely
The IO performance test with fio after removing the likely and unlikely macros in all if-statement shows no performance drop. They do not help for the performance of rnbd. The fio test did random read on 32 rnbd devices and 64 processes. Test environment: - AMD Opteron(tm) Processor 6386 SE - 125G memory - kernel version: 5.4.86 - gcc version: gcc (Debian 8.3.0-6) 8.3.0 - Infiniband controller: InfiniBand: Mellanox Technologies MT26428 [ConnectX VPI PCIe 2.0 5GT/s - IB QDR / 10GigE] (rev b0) before read: IOPS=549k, BW=2146MiB/s read: IOPS=544k, BW=2125MiB/s read: IOPS=553k, BW=2158MiB/s read: IOPS=535k, BW=2089MiB/s read: IOPS=543k, BW=2122MiB/s read: IOPS=552k, BW=2154MiB/s average: IOPS=546k, BW=2132MiB/s after read: IOPS=556k, BW=2172MiB/s read: IOPS=561k, BW=2191MiB/s read: IOPS=552k, BW=2156MiB/s read: IOPS=551k, BW=2154MiB/s read: IOPS=562k, BW=2194MiB/s ----------- average: IOPS=556k, BW=2173MiB/s The IOPS and bandwidth got better slightly after removing likely/unlikely. (IOPS= +1.8% BW= +1.9%) But we cannot make sure that removing the likely/unlikely help the performance because it depends on various situations. We only make sure that removing the likely/unlikely does not drop the performance. Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com> Reviewed-by: Md Haris Iqbal <haris.iqbal@ionos.com> Link: https://lore.kernel.org/r/20210428061359.206794-5-gi-oh.kim@ionos.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -241,7 +241,7 @@ static bool rnbd_rerun_if_needed(struct rnbd_clt_session *sess)
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cpu_q = rnbd_get_cpu_qlist(sess, nxt_cpu(cpu_q->cpu))) {
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if (!spin_trylock_irqsave(&cpu_q->requeue_lock, flags))
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continue;
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if (unlikely(!test_bit(cpu_q->cpu, sess->cpu_queues_bm)))
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if (!test_bit(cpu_q->cpu, sess->cpu_queues_bm))
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goto unlock;
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q = list_first_entry_or_null(&cpu_q->requeue_list,
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typeof(*q), requeue_list);
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@ -320,7 +320,7 @@ static struct rtrs_permit *rnbd_get_permit(struct rnbd_clt_session *sess,
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struct rtrs_permit *permit;
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permit = rtrs_clt_get_permit(sess->rtrs, con_type, wait);
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if (likely(permit))
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if (permit)
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/* We have a subtle rare case here, when all permits can be
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* consumed before busy counter increased. This is safe,
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* because loser will get NULL as a permit, observe 0 busy
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@ -355,7 +355,7 @@ static struct rnbd_iu *rnbd_get_iu(struct rnbd_clt_session *sess,
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return NULL;
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permit = rnbd_get_permit(sess, con_type, wait);
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if (unlikely(!permit)) {
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if (!permit) {
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kfree(iu);
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return NULL;
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}
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@ -1050,7 +1050,7 @@ static int rnbd_client_xfer_request(struct rnbd_clt_dev *dev,
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};
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err = rtrs_clt_request(rq_data_dir(rq), &req_ops, rtrs, permit,
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&vec, 1, size, iu->sgt.sgl, sg_cnt);
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if (unlikely(err)) {
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if (err) {
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rnbd_clt_err_rl(dev, "RTRS failed to transfer IO, err: %d\n",
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err);
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return err;
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@ -1081,7 +1081,7 @@ static bool rnbd_clt_dev_add_to_requeue(struct rnbd_clt_dev *dev,
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cpu_q = get_cpu_ptr(sess->cpu_queues);
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spin_lock_irqsave(&cpu_q->requeue_lock, flags);
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if (likely(!test_and_set_bit_lock(0, &q->in_list))) {
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if (!test_and_set_bit_lock(0, &q->in_list)) {
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if (WARN_ON(!list_empty(&q->requeue_list)))
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goto unlock;
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@ -1093,7 +1093,7 @@ static bool rnbd_clt_dev_add_to_requeue(struct rnbd_clt_dev *dev,
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*/
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smp_mb__before_atomic();
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}
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if (likely(atomic_read(&sess->busy))) {
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if (atomic_read(&sess->busy)) {
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list_add_tail(&q->requeue_list, &cpu_q->requeue_list);
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} else {
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/* Very unlikely, but possible: busy counter was
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@ -1121,7 +1121,7 @@ static void rnbd_clt_dev_kick_mq_queue(struct rnbd_clt_dev *dev,
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if (delay != RNBD_DELAY_IFBUSY)
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blk_mq_delay_run_hw_queue(hctx, delay);
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else if (unlikely(!rnbd_clt_dev_add_to_requeue(dev, q)))
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else if (!rnbd_clt_dev_add_to_requeue(dev, q))
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/*
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* If session is not busy we have to restart
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* the queue ourselves.
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@ -1138,12 +1138,12 @@ static blk_status_t rnbd_queue_rq(struct blk_mq_hw_ctx *hctx,
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int err;
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blk_status_t ret = BLK_STS_IOERR;
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if (unlikely(dev->dev_state != DEV_STATE_MAPPED))
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if (dev->dev_state != DEV_STATE_MAPPED)
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return BLK_STS_IOERR;
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iu->permit = rnbd_get_permit(dev->sess, RTRS_IO_CON,
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RTRS_PERMIT_NOWAIT);
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if (unlikely(!iu->permit)) {
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if (!iu->permit) {
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rnbd_clt_dev_kick_mq_queue(dev, hctx, RNBD_DELAY_IFBUSY);
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return BLK_STS_RESOURCE;
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}
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@ -1165,9 +1165,9 @@ static blk_status_t rnbd_queue_rq(struct blk_mq_hw_ctx *hctx,
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blk_mq_start_request(rq);
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err = rnbd_client_xfer_request(dev, rq, iu);
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if (likely(err == 0))
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if (err == 0)
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return BLK_STS_OK;
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if (unlikely(err == -EAGAIN || err == -ENOMEM)) {
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if (err == -EAGAIN || err == -ENOMEM) {
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rnbd_clt_dev_kick_mq_queue(dev, hctx, 10/*ms*/);
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ret = BLK_STS_RESOURCE;
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}
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@ -1584,7 +1584,7 @@ struct rnbd_clt_dev *rnbd_clt_map_device(const char *sessname,
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struct rnbd_clt_dev *dev;
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int ret;
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if (unlikely(exists_devpath(pathname, sessname)))
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if (exists_devpath(pathname, sessname))
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return ERR_PTR(-EEXIST);
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sess = find_and_get_or_create_sess(sessname, paths, path_cnt, port_nr, nr_poll_queues);
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@ -104,7 +104,7 @@ rnbd_get_sess_dev(int dev_id, struct rnbd_srv_session *srv_sess)
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rcu_read_lock();
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sess_dev = xa_load(&srv_sess->index_idr, dev_id);
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if (likely(sess_dev))
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if (sess_dev)
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ret = kref_get_unless_zero(&sess_dev->kref);
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rcu_read_unlock();
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