Currently btrfs raid1/10 balancer bаlance requests to mirrors,
based on pid % num of mirrors.
Make logic understood:
- if one of underline devices are non rotational
- Queue leght to underline devices
By default try use pid % num_mirrors guessing, but:
- If one of mirrors are non rotational, repick optimal to it
- If underline mirror have less queue leght then optimal,
repick to that mirror
For avoid round-robin request balancing,
lets round down queue leght:
- By 8 for rotational devs
- By 2 for all non rotational devs
Changes:
v1 -> v2:
- Use helper part_in_flight() from genhd.c
to get queue lenght
- Move guess code to guess_optimal()
- Change balancer logic, try use pid % mirror by default
Make balancing on spinning rust if one of underline devices
are overloaded
Signed-off-by: Timofey Titovets <nefelim...@gmail.com>
---
block/genhd.c | 1 +
fs/btrfs/volumes.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 115 insertions(+), 2 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index 96a66f671720..a7742bbbb6a7 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -81,6 +81,7 @@ void part_in_flight(struct request_queue *q, struct hd_struct
*part,
atomic_read(&part->in_flight[1]);
}
}
+EXPORT_SYMBOL_GPL(part_in_flight);
struct hd_struct *__disk_get_part(struct gendisk *disk, int partno)
{
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 9a04245003ab..1c84534df9a5 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -27,6 +27,7 @@
#include <linux/raid/pq.h>
#include <linux/semaphore.h>
#include <linux/uuid.h>
+#include <linux/genhd.h>
#include <asm/div64.h>
#include "ctree.h"
#include "extent_map.h"
@@ -5216,6 +5217,112 @@ int btrfs_is_parity_mirror(struct btrfs_fs_info
*fs_info, u64 logical, u64 len)
return ret;
}
+/**
+ * bdev_get_queue_len - return rounded down in flight queue lenght of bdev
+ *
+ * @bdev: target bdev
+ * @round_down: round factor big for hdd and small for ssd, like 8 and 2
+ */
+static int bdev_get_queue_len(struct block_device *bdev, int round_down)
+{
+ int sum;
+ struct hd_struct *bd_part = bdev->bd_part;
+ struct request_queue *rq = bdev_get_queue(bdev);
+ uint32_t inflight[2] = {0, 0};
+
+ part_in_flight(rq, bd_part, inflight);
+
+ sum = max_t(uint32_t, inflight[0], inflight[1]);
+
+ /*
+ * Try prevent switch for every sneeze
+ * By roundup output num by some value
+ */
+ return ALIGN_DOWN(sum, round_down);
+}
+
+/**
+ * guess_optimal - return guessed optimal mirror
+ *
+ * Optimal expected to be pid % num_stripes
+ *
+ * That's generaly ok for spread load
+ * Add some balancer based on queue leght to device
+ *
+ * Basic ideas:
+ * - Sequential read generate low amount of request
+ * so if load of drives are equal, use pid % num_stripes balancing
+ * - For mixed rotate/non-rotate mirrors, pick non-rotate as optimal
+ * and repick if other dev have "significant" less queue lenght
+ * - Repick optimal if queue leght of other mirror are less
+ */
+static int guess_optimal(struct map_lookup *map, int optimal)
+{
+ int i;
+ int round_down = 8;
+ int num = map->num_stripes;
+ int qlen[num];
+ bool is_nonrot[num];
+ bool all_bdev_nonrot = true;
+ bool all_bdev_rotate = true;
+ struct block_device *bdev;
+
+ if (num == 1)
+ return optimal;
+
+ /* Check accessible bdevs */
+ for (i = 0; i < num; i++) {
+ /* Init for missing bdevs */
+ is_nonrot[i] = false;
+ qlen[i] = INT_MAX;
+ bdev = map->stripes[i].dev->bdev;
+ if (bdev) {
+ qlen[i] = 0;
+ is_nonrot[i] = blk_queue_nonrot(bdev_get_queue(bdev));
+ if (is_nonrot[i])
+ all_bdev_rotate = false;
+ else
+ all_bdev_nonrot = false;
+ }
+ }
+
+ /*
+ * Don't bother with computation
+ * if only one of two bdevs are accessible
+ */
+ if (num == 2 && qlen[0] != qlen[1]) {
+ if (qlen[0] < qlen[1])
+ return 0;
+ else
+ return 1;
+ }
+
+ if (all_bdev_nonrot)
+ round_down = 2;
+
+ for (i = 0; i < num; i++) {
+ if (qlen[i])
+ continue;
+ bdev = map->stripes[i].dev->bdev;
+ qlen[i] = bdev_get_queue_len(bdev, round_down);
+ }
+
+ /* For mixed case, pick non rotational dev as optimal */
+ if (all_bdev_rotate == all_bdev_nonrot) {
+ for (i = 0; i < num; i++) {
+ if (is_nonrot[i])
+ optimal = i;
+ }
+ }
+
+ for (i = 0; i < num; i++) {
+ if (qlen[optimal] > qlen[i])
+ optimal = i;
+ }
+
+ return optimal;
+}
+
static int find_live_mirror(struct btrfs_fs_info *fs_info,
struct map_lookup *map, int first, int num,
int optimal, int dev_replace_is_ongoing)
@@ -5664,6 +5771,7 @@ static int __btrfs_map_block(struct btrfs_fs_info
*fs_info,
int i;
int ret = 0;
int num_stripes;
+ int optimal;
int max_errors = 0;
int tgtdev_indexes = 0;
struct btrfs_bio *bbio = NULL;
@@ -5776,9 +5884,11 @@ static int __btrfs_map_block(struct btrfs_fs_info
*fs_info,
else if (mirror_num)
stripe_index = mirror_num - 1;
else {
+ optimal = guess_optimal(map,
+ current->pid % map->num_stripes);
stripe_index = find_live_mirror(fs_info, map, 0,
map->num_stripes,
- current->pid % map->num_stripes,
+ optimal,
dev_replace_is_ongoing);
mirror_num = stripe_index + 1;
}
@@ -5804,10 +5914,12 @@ static int __btrfs_map_block(struct btrfs_fs_info
*fs_info,
stripe_index += mirror_num - 1;
else {
int old_stripe_index = stripe_index;
+ optimal = guess_optimal(map,
+ current->pid % map->num_stripes);
stripe_index = find_live_mirror(fs_info, map,
stripe_index,
map->sub_stripes, stripe_index +
- current->pid % map->sub_stripes,
+ optimal,
dev_replace_is_ongoing);
mirror_num = stripe_index - old_stripe_index + 1;
}
--
2.15.1
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