aboutsummaryrefslogtreecommitdiffstats
path: root/fs/nfs
diff options
context:
space:
mode:
authorTrond Myklebust <Trond.Myklebust@netapp.com>2012-12-02 13:54:59 -0500
committerTrond Myklebust <Trond.Myklebust@netapp.com>2012-12-06 00:30:53 +0100
commit1fa8064429d0acbf5bbf3c8a53f65679fdacc75e (patch)
tree86e9c0420815d6029c47d836bf3d7a4c93098c3c /fs/nfs
parentc05eecf636101dd4347b2d8fa457626bf0088e0a (diff)
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>
Diffstat (limited to 'fs/nfs')
-rw-r--r--fs/nfs/nfs4session.c63
-rw-r--r--fs/nfs/nfs4session.h2
2 files changed, 60 insertions, 5 deletions
diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c
index 066cfa101b4..ed5aa9fa9c7 100644
--- a/fs/nfs/nfs4session.c
+++ b/fs/nfs/nfs4session.c
@@ -178,6 +178,8 @@ static void nfs4_reset_slot_table(struct nfs4_slot_table *tbl,
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 @@ void nfs41_set_target_slotid(struct nfs4_slot_table *tbl,
{
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 @@ static void nfs41_set_server_slotid_locked(struct nfs4_slot_table *tbl,
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);
}
diff --git a/fs/nfs/nfs4session.h b/fs/nfs/nfs4session.h
index 7db73937016..04f834cab16 100644
--- a/fs/nfs/nfs4session.h
+++ b/fs/nfs/nfs4session.h
@@ -38,6 +38,8 @@ struct nfs4_slot_table {
* op for dynamic resizing */
u32 target_highest_slotid; /* Server max_slot target */
u32 server_highest_slotid; /* Server highest slotid */
+ s32 d_target_highest_slotid; /* Derivative */
+ s32 d2_target_highest_slotid; /* 2nd derivative */
unsigned long generation; /* Generation counter for
target_highest_slotid */
struct completion complete;