NFSv4.1: Try to eliminate outliers when updating target_highest_slotid
Look for sudden changes in the first and second derivatives in order
to eliminate outlier changes to target_highest_slotid (which are
due to out-of-order RPC replies).
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c
index 066cfa1..ed5aa9f 100644
--- a/fs/nfs/nfs4session.c
+++ b/fs/nfs/nfs4session.c
@@ -178,6 +178,8 @@
tbl->highest_used_slotid = NFS4_NO_SLOT;
tbl->target_highest_slotid = server_highest_slotid;
tbl->server_highest_slotid = server_highest_slotid;
+ tbl->d_target_highest_slotid = 0;
+ tbl->d2_target_highest_slotid = 0;
tbl->max_slotid = server_highest_slotid;
}
@@ -292,6 +294,8 @@
{
spin_lock(&tbl->slot_tbl_lock);
nfs41_set_target_slotid_locked(tbl, target_highest_slotid);
+ tbl->d_target_highest_slotid = 0;
+ tbl->d2_target_highest_slotid = 0;
spin_unlock(&tbl->slot_tbl_lock);
}
@@ -307,16 +311,65 @@
tbl->server_highest_slotid = highest_slotid;
}
+static s32 nfs41_derivative_target_slotid(s32 s1, s32 s2)
+{
+ s1 -= s2;
+ if (s1 == 0)
+ return 0;
+ if (s1 < 0)
+ return (s1 - 1) >> 1;
+ return (s1 + 1) >> 1;
+}
+
+static int nfs41_sign_s32(s32 s1)
+{
+ if (s1 > 0)
+ return 1;
+ if (s1 < 0)
+ return -1;
+ return 0;
+}
+
+static bool nfs41_same_sign_or_zero_s32(s32 s1, s32 s2)
+{
+ if (!s1 || !s2)
+ return true;
+ return nfs41_sign_s32(s1) == nfs41_sign_s32(s2);
+}
+
+/* Try to eliminate outliers by checking for sharp changes in the
+ * derivatives and second derivatives
+ */
+static bool nfs41_is_outlier_target_slotid(struct nfs4_slot_table *tbl,
+ u32 new_target)
+{
+ s32 d_target, d2_target;
+ bool ret = true;
+
+ d_target = nfs41_derivative_target_slotid(new_target,
+ tbl->target_highest_slotid);
+ d2_target = nfs41_derivative_target_slotid(d_target,
+ tbl->d_target_highest_slotid);
+ /* Is first derivative same sign? */
+ if (nfs41_same_sign_or_zero_s32(d_target, tbl->d_target_highest_slotid))
+ ret = false;
+ /* Is second derivative same sign? */
+ if (nfs41_same_sign_or_zero_s32(d2_target, tbl->d2_target_highest_slotid))
+ ret = false;
+ tbl->d_target_highest_slotid = d_target;
+ tbl->d2_target_highest_slotid = d2_target;
+ return ret;
+}
+
void nfs41_update_target_slotid(struct nfs4_slot_table *tbl,
struct nfs4_slot *slot,
struct nfs4_sequence_res *res)
{
spin_lock(&tbl->slot_tbl_lock);
- if (tbl->generation != slot->generation)
- goto out;
- nfs41_set_server_slotid_locked(tbl, res->sr_highest_slotid);
- nfs41_set_target_slotid_locked(tbl, res->sr_target_highest_slotid);
-out:
+ if (!nfs41_is_outlier_target_slotid(tbl, res->sr_target_highest_slotid))
+ nfs41_set_target_slotid_locked(tbl, res->sr_target_highest_slotid);
+ if (tbl->generation == slot->generation)
+ nfs41_set_server_slotid_locked(tbl, res->sr_highest_slotid);
spin_unlock(&tbl->slot_tbl_lock);
}