On 5/10/24 09:11, Damien Le Moal wrote:
On 5/10/24 05:43, John Meneghini wrote:From: Hannes Reinecke <hare@xxxxxxxxxx> Add a new option 'BLK_NODE_LATENCY' to track per-node I/O latency. This can be used by I/O schedulers to determine the 'best' queue to send I/O to. Signed-off-by: Hannes Reinecke <hare@xxxxxxxxxx> Cleaned up checkpatch warnings and updated MAINTAINERS.This note should be before Hannes SoB. E.g: [John] Fixed checkpatch warnings and updated MAINTAINERS.Signed-off-by: John Meneghini <jmeneghi@xxxxxxxxxx> --- MAINTAINERS | 1 + block/Kconfig | 9 + block/Makefile | 1 + block/blk-mq-debugfs.c | 2 + block/blk-nlatency.c | 389 +++++++++++++++++++++++++++++++++++++++++ block/blk-rq-qos.h | 6 + include/linux/blk-mq.h | 11 ++ 7 files changed, 419 insertions(+) create mode 100644 block/blk-nlatency.c diff --git a/MAINTAINERS b/MAINTAINERS index 7c121493f43d..a4634365c82f 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5405,6 +5405,7 @@ F: block/bfq-cgroup.c F: block/blk-cgroup.c F: block/blk-iocost.c F: block/blk-iolatency.c +F: block/blk-nlatency.c F: block/blk-throttle.c F: include/linux/blk-cgroup.hdiff --git a/block/Kconfig b/block/Kconfigindex 1de4682d48cc..641ed39d609c 100644 --- a/block/Kconfig +++ b/block/Kconfig @@ -186,6 +186,15 @@ config BLK_CGROUP_IOPRIO scheduler and block devices process requests. Only some I/O schedulers and some block devices support I/O priorities.+config BLK_NODE_LATENCY+ bool "Track per-node I/O latency" + help + Enable per-node I/O latency tracking for multipathing. This uses the + blk-nodelat latency tracker to provide latencies for each node, and schedules + I/O on the path with the least latency for the submitting node. This can be + used by I/O schedulers to determine the node with the least latency. Currently + only supports nvme over fabrics devices. + config BLK_DEBUG_FS bool "Block layer debugging information in debugfs" default y diff --git a/block/Makefile b/block/Makefile index 46ada9dc8bbf..9d2e71a3e36f 100644 --- a/block/Makefile +++ b/block/Makefile @@ -21,6 +21,7 @@ obj-$(CONFIG_BLK_DEV_THROTTLING) += blk-throttle.o obj-$(CONFIG_BLK_CGROUP_IOPRIO) += blk-ioprio.o obj-$(CONFIG_BLK_CGROUP_IOLATENCY) += blk-iolatency.o obj-$(CONFIG_BLK_CGROUP_IOCOST) += blk-iocost.o +obj-$(CONFIG_BLK_NODE_LATENCY) += blk-nlatency.oLet's keep the alignment please.obj-$(CONFIG_MQ_IOSCHED_DEADLINE) += mq-deadline.o obj-$(CONFIG_MQ_IOSCHED_KYBER) += kyber-iosched.o bfq-y := bfq-iosched.o bfq-wf2q.o bfq-cgroup.o diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index 94668e72ab09..cb38228b95d8 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -762,6 +762,8 @@ static const char *rq_qos_id_to_name(enum rq_qos_id id) return "latency"; case RQ_QOS_COST: return "cost"; + case RQ_QOS_NLAT: + return "node-latency"; } return "unknown"; } diff --git a/block/blk-nlatency.c b/block/blk-nlatency.c new file mode 100644 index 000000000000..219c3f636d76 --- /dev/null +++ b/block/blk-nlatency.c @@ -0,0 +1,389 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Per-node request latency tracking. + * + * Copyright (C) 2023 Hannes Reinecke + * + * A simple per-node latency tracker for use by I/O scheduler. + * Latencies are measures over 'win_usec' microseconds and stored per node. + * If the number of measurements falls below 'lowat' the measurement is + * assumed to be unreliable and will become 'stale'. + * These 'stale' latencies can be 'decayed', where during each measurement + * interval the 'stale' latency value is decreased by 'decay' percent. + * Once the 'stale' latency reaches zero it will be updated by the + * measured latency. + */ +#include <linux/kernel.h> +#include <linux/blk_types.h> +#include <linux/slab.h> + +#include "blk-stat.h" +#include "blk-rq-qos.h" +#include "blk.h" + +#define NLAT_DEFAULT_LOWAT 2 +#define NLAT_DEFAULT_DECAY 50 + +struct rq_nlat { + struct rq_qos rqos; + + u64 win_usec; /* latency measurement window in microseconds */Using microseconds forces you to do costly multiplications and divisions by 1000. Why not keep things in nanoseconds ?
I wanted to keep the user interface simple; entering nanoseconds values is tedious. But sure, I can change it.
+ unsigned int lowat; /* Low Watermark latency measurement */ + unsigned int decay; /* Percentage for 'decaying' latencies */ + bool enabled; + + struct blk_stat_callback *cb; + + unsigned int num; + u64 *latency; + unsigned int *samples; +}; + +static inline struct rq_nlat *RQNLAT(struct rq_qos *rqos) +{ + return container_of(rqos, struct rq_nlat, rqos); +} + +static u64 nlat_default_latency_usec(struct request_queue *q) +{ + /* + * We default to 2msec for non-rotational storage, and 75msec + * for rotational storage. + */ + if (blk_queue_nonrot(q)) + return 2000ULL; + elseNo need for this else.
OK.
+ return 75000ULL; +} + +static void nlat_timer_fn(struct blk_stat_callback *cb) +{ + struct rq_nlat *nlat = cb->data; + int n; + + for (n = 0; n < cb->buckets; n++) { + if (cb->stat[n].nr_samples < nlat->lowat) { + /* + * 'decay' the latency by the specified + * percentage to ensure the queues are + * being tested to balance out temporary + * latency spikes. + */ + nlat->latency[n] = + div64_u64(nlat->latency[n] * nlat->decay, 100); + } else + nlat->latency[n] = cb->stat[n].mean;Missing the curly brackets around the else block. Nit: n is a rather unusual name for a loop index. Why not the usual "i" ? Does notmatter much though.
There was a reason once ... but yeah, let's move to 'i'.
+ nlat->samples[n] = cb->stat[n].nr_samples; + } + if (nlat->enabled) + blk_stat_activate_nsecs(nlat->cb, nlat->win_usec * 1000); +} + +static int nlat_bucket_node(const struct request *rq) +{ + if (!rq->mq_ctx) + return -1; + return cpu_to_node(blk_mq_rq_cpu((struct request *)rq)); +} + +static void nlat_exit(struct rq_qos *rqos) +{ + struct rq_nlat *nlat = RQNLAT(rqos); + + blk_stat_remove_callback(nlat->rqos.disk->queue, nlat->cb); + blk_stat_free_callback(nlat->cb); + kfree(nlat->samples); + kfree(nlat->latency); + kfree(nlat); +} + +#ifdef CONFIG_BLK_DEBUG_FS +static int nlat_win_usec_show(void *data, struct seq_file *m) +{ + struct rq_qos *rqos = data; + struct rq_nlat *nlat = RQNLAT(rqos); + + seq_printf(m, "%llu\n", nlat->win_usec); + return 0; +} + +static ssize_t nlat_win_usec_write(void *data, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct rq_qos *rqos = data; + struct rq_nlat *nlat = RQNLAT(rqos); + char val[16] = { }; + u64 usec; + int err; + + if (blk_queue_dying(nlat->rqos.disk->queue)) + return -ENOENT; + + if (count >= sizeof(val)) + return -EINVAL; + + if (copy_from_user(val, buf, count)) + return -EFAULT; + + err = kstrtoull(val, 10, &usec); + if (err) + return err; + blk_stat_deactivate(nlat->cb); + nlat->win_usec = usec; + blk_stat_activate_nsecs(nlat->cb, nlat->win_usec * 1000); + + return count; +} + +static int nlat_lowat_show(void *data, struct seq_file *m) +{ + struct rq_qos *rqos = data; + struct rq_nlat *nlat = RQNLAT(rqos); + + seq_printf(m, "%u\n", nlat->lowat); + return 0; +} + +static ssize_t nlat_lowat_write(void *data, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct rq_qos *rqos = data; + struct rq_nlat *nlat = RQNLAT(rqos); + char val[16] = { }; + unsigned int lowat; + int err; + + if (blk_queue_dying(nlat->rqos.disk->queue)) + return -ENOENT; + + if (count >= sizeof(val)) + return -EINVAL; + + if (copy_from_user(val, buf, count)) + return -EFAULT; + + err = kstrtouint(val, 10, &lowat); + if (err) + return err; + blk_stat_deactivate(nlat->cb); + nlat->lowat = lowat; + blk_stat_activate_nsecs(nlat->cb, nlat->win_usec * 1000); + + return count; +} + +static int nlat_decay_show(void *data, struct seq_file *m) +{ + struct rq_qos *rqos = data; + struct rq_nlat *nlat = RQNLAT(rqos); + + seq_printf(m, "%u\n", nlat->decay); + return 0; +} + +static ssize_t nlat_decay_write(void *data, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct rq_qos *rqos = data; + struct rq_nlat *nlat = RQNLAT(rqos); + char val[16] = { }; + unsigned int decay; + int err; + + if (blk_queue_dying(nlat->rqos.disk->queue)) + return -ENOENT; + + if (count >= sizeof(val)) + return -EINVAL; + + if (copy_from_user(val, buf, count)) + return -EFAULT; + + err = kstrtouint(val, 10, &decay); + if (err) + return err; + if (decay > 100) + return -EINVAL; + blk_stat_deactivate(nlat->cb); + nlat->decay = decay; + blk_stat_activate_nsecs(nlat->cb, nlat->win_usec * 1000); + + return count; +} + +static int nlat_enabled_show(void *data, struct seq_file *m) +{ + struct rq_qos *rqos = data; + struct rq_nlat *nlat = RQNLAT(rqos); + + seq_printf(m, "%d\n", nlat->enabled); + return 0; +} + +static int nlat_id_show(void *data, struct seq_file *m) +{ + struct rq_qos *rqos = data; + + seq_printf(m, "%u\n", rqos->id); + return 0; +} + +static int nlat_latency_show(void *data, struct seq_file *m) +{ + struct rq_qos *rqos = data; + struct rq_nlat *nlat = RQNLAT(rqos); + int n; + + if (!nlat->enabled) + return 0; + + for (n = 0; n < nlat->num; n++) { + if (n > 0) + seq_puts(m, " "); + seq_printf(m, "%llu", nlat->latency[n]); + } + seq_puts(m, "\n"); + return 0; +} + +static int nlat_samples_show(void *data, struct seq_file *m) +{ + struct rq_qos *rqos = data; + struct rq_nlat *nlat = RQNLAT(rqos); + int n; + + if (!nlat->enabled) + return 0; + + for (n = 0; n < nlat->num; n++) { + if (n > 0) + seq_puts(m, " "); + seq_printf(m, "%u", nlat->samples[n]); + } + seq_puts(m, "\n"); + return 0; +} + +static const struct blk_mq_debugfs_attr nlat_debugfs_attrs[] = { + {"win_usec", 0600, nlat_win_usec_show, nlat_win_usec_write}, + {"lowat", 0600, nlat_lowat_show, nlat_lowat_write}, + {"decay", 0600, nlat_decay_show, nlat_decay_write}, + {"enabled", 0400, nlat_enabled_show}, + {"id", 0400, nlat_id_show}, + {"latency", 0400, nlat_latency_show}, + {"samples", 0400, nlat_samples_show}, + {}, +}; +#endif + +static const struct rq_qos_ops nlat_rqos_ops = { + .exit = nlat_exit, +#ifdef CONFIG_BLK_DEBUG_FS + .debugfs_attrs = nlat_debugfs_attrs, +#endif +}; + +u64 blk_nlat_latency(struct gendisk *disk, int node) +{ + struct rq_qos *rqos; + struct rq_nlat *nlat; + + rqos = nlat_rq_qos(disk->queue); + if (!rqos) + return 0; + nlat = RQNLAT(rqos); + if (node > nlat->num) + return 0; + + return div64_u64(nlat->latency[node], 1000);See comment at the top. Why not keep everything in nanoseconds to avoid this costly division ?
Agreed.
+} +EXPORT_SYMBOL_GPL(blk_nlat_latency); + +int blk_nlat_enable(struct gendisk *disk) +{ + struct rq_qos *rqos; + struct rq_nlat *nlat; + + /* Latency tracking not enabled? */ + rqos = nlat_rq_qos(disk->queue); + if (!rqos) + return -EINVAL; + nlat = RQNLAT(rqos); + if (nlat->enabled) + return 0; + + /* Queue not registered? Maybe shutting down... */ + if (!blk_queue_registered(disk->queue)) + return -EAGAIN; + + nlat->enabled = true; + memset(nlat->latency, 0, sizeof(u64) * nlat->num); + memset(nlat->samples, 0, sizeof(unsigned int) * nlat->num); + blk_stat_activate_nsecs(nlat->cb, nlat->win_usec * 1000); + + return 0; +} +EXPORT_SYMBOL_GPL(blk_nlat_enable); + +void blk_nlat_disable(struct gendisk *disk) +{ + struct rq_qos *rqos = nlat_rq_qos(disk->queue); + struct rq_nlat *nlat; + + if (!rqos) + return; + nlat = RQNLAT(rqos); + if (nlat->enabled) { + blk_stat_deactivate(nlat->cb); + nlat->enabled = false; + } +} +EXPORT_SYMBOL_GPL(blk_nlat_disable); + +int blk_nlat_init(struct gendisk *disk) +{ + struct rq_nlat *nlat; + int ret = -ENOMEM; + + nlat = kzalloc(sizeof(*nlat), GFP_KERNEL); + if (!nlat) + return -ENOMEM; + + nlat->num = num_possible_nodes(); + nlat->lowat = NLAT_DEFAULT_LOWAT; + nlat->decay = NLAT_DEFAULT_DECAY; + nlat->win_usec = nlat_default_latency_usec(disk->queue); + + nlat->latency = kcalloc(nlat->num, sizeof(u64), GFP_KERNEL); + if (!nlat->latency) + goto err_free; + nlat->samples = kcalloc(nlat->num, sizeof(unsigned int), GFP_KERNEL); + if (!nlat->samples) + goto err_free; + nlat->cb = blk_stat_alloc_callback(nlat_timer_fn, nlat_bucket_node, + nlat->num, nlat); + if (!nlat->cb) + goto err_free; + + /* + * Assign rwb and add the stats callback. + */This can be a single line comment.
Ok.
+ mutex_lock(&disk->queue->rq_qos_mutex); + ret = rq_qos_add(&nlat->rqos, disk, RQ_QOS_NLAT, &nlat_rqos_ops); + mutex_unlock(&disk->queue->rq_qos_mutex); + if (ret) + goto err_free_cb; + + blk_stat_add_callback(disk->queue, nlat->cb); + + return 0; + +err_free_cb: + blk_stat_free_callback(nlat->cb); +err_free: + kfree(nlat->samples); + kfree(nlat->latency); + kfree(nlat); + return ret; +} +EXPORT_SYMBOL_GPL(blk_nlat_init); diff --git a/block/blk-rq-qos.h b/block/blk-rq-qos.h index 37245c97ee61..2fc11ced0c00 100644 --- a/block/blk-rq-qos.h +++ b/block/blk-rq-qos.h @@ -17,6 +17,7 @@ enum rq_qos_id { RQ_QOS_WBT, RQ_QOS_LATENCY, RQ_QOS_COST, + RQ_QOS_NLAT, };struct rq_wait {@@ -79,6 +80,11 @@ static inline struct rq_qos *iolat_rq_qos(struct request_queue *q) return rq_qos_id(q, RQ_QOS_LATENCY); }+static inline struct rq_qos *nlat_rq_qos(struct request_queue *q)+{ + return rq_qos_id(q, RQ_QOS_NLAT); +} + static inline void rq_wait_init(struct rq_wait *rq_wait) { atomic_set(&rq_wait->inflight, 0); diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index d3d8fd8e229b..1f3829627f1b 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -1231,4 +1231,15 @@ static inline bool blk_req_can_dispatch_to_zone(struct request *rq) } #endif /* CONFIG_BLK_DEV_ZONED */+#ifdef CONFIG_BLK_NODE_LATENCY+int blk_nlat_enable(struct gendisk *disk); +void blk_nlat_disable(struct gendisk *disk); +u64 blk_nlat_latency(struct gendisk *disk, int node); +int blk_nlat_init(struct gendisk *disk); +#else +static inline int blk_nlat_enable(struct gendisk *disk) { return 0; } +static inline void blk_nlat_disable(struct gendisk *disk) {} +static inline u64 blk_nlat_latency(struct gendisk *disk, int node) { return 0; } +static inline int blk_nlat_init(struct gendisk *disk) { return -EOPNOTSUPP; } +#endif #endif /* BLK_MQ_H */
Thanks for the review! Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@xxxxxxx +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Ivo Totev, Andrew McDonald, Werner Knoblich