btrfs: calculate discard delay based on number of extents
An earlier patch keeps track of discardable_extents. These are
undiscarded extents managed by the free space cache. Here, we will use
this to dynamically calculate the discard delay interval.
There are 3 rate to consider. The first is the target convergence rate,
the rate to discard all discardable_extents over the
BTRFS_DISCARD_TARGET_MSEC time frame. This is clamped by the lower
limit, the iops limit or BTRFS_DISCARD_MIN_DELAY (1ms), and the upper
limit, BTRFS_DISCARD_MAX_DELAY (1s). We reevaluate this delay every
transaction commit.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index ce1da3f..4155174 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -366,9 +366,40 @@ static ssize_t btrfs_discardable_extents_show(struct kobject *kobj,
}
BTRFS_ATTR(discard, discardable_extents, btrfs_discardable_extents_show);
+static ssize_t btrfs_discard_iops_limit_show(struct kobject *kobj,
+ struct kobj_attribute *a,
+ char *buf)
+{
+ struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+ return snprintf(buf, PAGE_SIZE, "%u\n",
+ READ_ONCE(fs_info->discard_ctl.iops_limit));
+}
+
+static ssize_t btrfs_discard_iops_limit_store(struct kobject *kobj,
+ struct kobj_attribute *a,
+ const char *buf, size_t len)
+{
+ struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+ struct btrfs_discard_ctl *discard_ctl = &fs_info->discard_ctl;
+ u32 iops_limit;
+ int ret;
+
+ ret = kstrtou32(buf, 10, &iops_limit);
+ if (ret)
+ return -EINVAL;
+
+ WRITE_ONCE(discard_ctl->iops_limit, iops_limit);
+
+ return len;
+}
+BTRFS_ATTR_RW(discard, iops_limit, btrfs_discard_iops_limit_show,
+ btrfs_discard_iops_limit_store);
+
static const struct attribute *discard_debug_attrs[] = {
BTRFS_ATTR_PTR(discard, discardable_bytes),
BTRFS_ATTR_PTR(discard, discardable_extents),
+ BTRFS_ATTR_PTR(discard, iops_limit),
NULL,
};