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author | Trond Myklebust <Trond.Myklebust@netapp.com> | 2012-12-02 22:54:59 +0400 |
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committer | Trond Myklebust <Trond.Myklebust@netapp.com> | 2012-12-06 03:30:53 +0400 |
commit | 1fa8064429d0acbf5bbf3c8a53f65679fdacc75e (patch) | |
tree | 86e9c0420815d6029c47d836bf3d7a4c93098c3c /fs/nfs/nfs4session.c | |
parent | c05eecf636101dd4347b2d8fa457626bf0088e0a (diff) | |
download | linux-1fa8064429d0acbf5bbf3c8a53f65679fdacc75e.tar.xz |
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/nfs4session.c')
-rw-r--r-- | fs/nfs/nfs4session.c | 63 |
1 files changed, 58 insertions, 5 deletions
diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c index 066cfa101b41..ed5aa9fa9c7b 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); } |