Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*

 * linux/net/sunrpc/timer.c

 *

 * Estimate RPC request round trip time.

 *

 * Based on packet round-trip and variance estimator algorithms described

 * in appendix A of "Congestion Avoidance and Control" by Van Jacobson

 * and Michael J. Karels (ACM Computer Communication Review; Proceedings

 * of the Sigcomm '88 Symposium in Stanford, CA, August, 1988).

 *

 * This RTT estimator is used only for RPC over datagram protocols.

 *

 * Copyright (C) 2002 Trond Myklebust <trond.myklebust@fys.uio.no>

 */

#include <asm/param.h>

#include <linux/types.h>

#include <linux/unistd.h>

#include <linux/module.h>

#include <linux/sunrpc/clnt.h>

#define RPC_RTO_MAX (60*HZ)

#define RPC_RTO_INIT (HZ/5)

#define RPC_RTO_MIN (HZ/10)

void

rpc_init_rtt(struct rpc_rtt *rt, unsigned long timeo)

{

        unsigned long init = 0;

        unsigned i;

        rt->timeo = timeo;

        if (timeo > RPC_RTO_INIT)

                init = (timeo - RPC_RTO_INIT) << 3;

        for (i = 0; i < 5; i++) {

                rt->srtt[i] = init;

                rt->sdrtt[i] = RPC_RTO_INIT;

                rt->ntimeouts[i] = 0;

        }

}

EXPORT_SYMBOL_GPL(rpc_init_rtt);

/*

 * NB: When computing the smoothed RTT and standard deviation,

 *     be careful not to produce negative intermediate results.

 */

void

rpc_update_rtt(struct rpc_rtt *rt, unsigned timer, long m)

{

        long *srtt, *sdrtt;

        if (timer-- == 0)

                return;

        /* jiffies wrapped; ignore this one */

        if (m < 0)

                return;

        if (m == 0)

                m = 1L;

        srtt = (long *)&rt->srtt[timer];

        m -= *srtt >> 3;

        *srtt += m;

        if (m < 0)

                m = -m;

        sdrtt = (long *)&rt->sdrtt[timer];

        m -= *sdrtt >> 2;

        *sdrtt += m;

        /* Set lower bound on the variance */

        if (*sdrtt < RPC_RTO_MIN)

                *sdrtt = RPC_RTO_MIN;

}

EXPORT_SYMBOL_GPL(rpc_update_rtt);

/*

 * Estimate rto for an nfs rpc sent via. an unreliable datagram.

 * Use the mean and mean deviation of rtt for the appropriate type of rpc

 * for the frequent rpcs and a default for the others.

 * The justification for doing "other" this way is that these rpcs

 * happen so infrequently that timer est. would probably be stale.

 * Also, since many of these rpcs are

 * non-idempotent, a conservative timeout is desired.

 * getattr, lookup,

 * read, write, commit     - A+4D

 * other                   - timeo

 */

unsigned long

rpc_calc_rto(struct rpc_rtt *rt, unsigned timer)

{

        unsigned long res;

        if (timer-- == 0)

                return rt->timeo;

        res = ((rt->srtt[timer] + 7) >> 3) + rt->sdrtt[timer];

        if (res > RPC_RTO_MAX)

                res = RPC_RTO_MAX;

        return res;

}

EXPORT_SYMBOL_GPL(rpc_calc_rto);