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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>
This commit is contained in:
Trond Myklebust 2012-12-02 13:54:59 -05:00
parent c05eecf636
commit 1fa8064429
2 changed files with 60 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

63
fs/nfs/nfs4session.c
View File

@ -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);
}

2
fs/nfs/nfs4session.h
View File

@ -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;