106 строки
2.3 KiB
C
106 строки
2.3 KiB
C
|
/*
|
||
|
|
* 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/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;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* 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;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* 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;
|
||
|
|
}
|