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authorDennis Zhou <dennis@kernel.org>2020-01-02 16:26:35 -0500
committerDavid Sterba <dsterba@suse.com>2020-01-20 16:40:59 +0100
commita2309300841207de28307ecd2f0e031fccde37a3 (patch)
tree8f84e7b531380c5330ac456baaedd5956998682d /fs/btrfs/discard.c
parent5dc7c10b87474c98116d3438739743cd77263e9f (diff)
downloadlinux-a2309300841207de28307ecd2f0e031fccde37a3.tar.bz2
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>
Diffstat (limited to 'fs/btrfs/discard.c')
-rw-r--r--fs/btrfs/discard.c55
1 files changed, 51 insertions, 4 deletions
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index 62298a438fa5..29645676427b 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -15,6 +15,12 @@
#define BTRFS_DISCARD_DELAY (120ULL * NSEC_PER_SEC)
#define BTRFS_DISCARD_UNUSED_DELAY (10ULL * NSEC_PER_SEC)
+/* Target completion latency of discarding all discardable extents */
+#define BTRFS_DISCARD_TARGET_MSEC (6 * 60 * 60UL * MSEC_PER_SEC)
+#define BTRFS_DISCARD_MIN_DELAY_MSEC (1UL)
+#define BTRFS_DISCARD_MAX_DELAY_MSEC (1000UL)
+#define BTRFS_DISCARD_MAX_IOPS (10U)
+
static struct list_head *get_discard_list(struct btrfs_discard_ctl *discard_ctl,
struct btrfs_block_group *block_group)
{
@@ -235,11 +241,17 @@ void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
block_group = find_next_block_group(discard_ctl, now);
if (block_group) {
- u64 delay = 0;
+ unsigned long delay = discard_ctl->delay;
+
+ /*
+ * This timeout is to hopefully prevent immediate discarding
+ * in a recently allocated block group.
+ */
+ if (now < block_group->discard_eligible_time) {
+ u64 bg_timeout = block_group->discard_eligible_time - now;
- if (now < block_group->discard_eligible_time)
- delay = nsecs_to_jiffies(
- block_group->discard_eligible_time - now);
+ delay = max(delay, nsecs_to_jiffies(bg_timeout));
+ }
mod_delayed_work(discard_ctl->discard_workers,
&discard_ctl->work, delay);
@@ -343,6 +355,39 @@ bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl)
}
/**
+ * btrfs_discard_calc_delay - recalculate the base delay
+ * @discard_ctl: discard control
+ *
+ * Recalculate the base delay which is based off the total number of
+ * discardable_extents. Clamp this between the lower_limit (iops_limit or 1ms)
+ * and the upper_limit (BTRFS_DISCARD_MAX_DELAY_MSEC).
+ */
+void btrfs_discard_calc_delay(struct btrfs_discard_ctl *discard_ctl)
+{
+ s32 discardable_extents;
+ u32 iops_limit;
+ unsigned long delay;
+ unsigned long lower_limit = BTRFS_DISCARD_MIN_DELAY_MSEC;
+
+ discardable_extents = atomic_read(&discard_ctl->discardable_extents);
+ if (!discardable_extents)
+ return;
+
+ spin_lock(&discard_ctl->lock);
+
+ iops_limit = READ_ONCE(discard_ctl->iops_limit);
+ if (iops_limit)
+ lower_limit = max_t(unsigned long, lower_limit,
+ MSEC_PER_SEC / iops_limit);
+
+ delay = BTRFS_DISCARD_TARGET_MSEC / discardable_extents;
+ delay = clamp(delay, lower_limit, BTRFS_DISCARD_MAX_DELAY_MSEC);
+ discard_ctl->delay = msecs_to_jiffies(delay);
+
+ spin_unlock(&discard_ctl->lock);
+}
+
+/**
* btrfs_discard_update_discardable - propagate discard counters
* @block_group: block_group of interest
* @ctl: free_space_ctl of @block_group
@@ -464,6 +509,8 @@ void btrfs_discard_init(struct btrfs_fs_info *fs_info)
atomic_set(&discard_ctl->discardable_extents, 0);
atomic64_set(&discard_ctl->discardable_bytes, 0);
+ discard_ctl->delay = BTRFS_DISCARD_MAX_DELAY_MSEC;
+ discard_ctl->iops_limit = BTRFS_DISCARD_MAX_IOPS;
}
void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)