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Commit 1fa80644 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

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: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent c05eecf6

fs/nfs/nfs4session.c

+58 −5
Original line number Diff line number Diff line
@@ -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);

	if (!nfs41_is_outlier_target_slotid(tbl, res->sr_target_highest_slotid))

		nfs41_set_target_slotid_locked(tbl, res->sr_target_highest_slotid);

out:

	if (tbl->generation == slot->generation)

		nfs41_set_server_slotid_locked(tbl, res->sr_highest_slotid);

	spin_unlock(&tbl->slot_tbl_lock);

}

fs/nfs/nfs4session.h

+2 −0
Original line number Diff line number Diff line
@@ -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;