ia64/linux-2.6.18-xen.hg

view net/sunrpc/timer.c @ 871:9cbcc9008446

xen/x86: don't initialize cpu_data[]'s apicid field on generic code

Afaict, this is not only redundant with the intialization done in
drivers/xen/core/smpboot.c, but actually results - at least for
secondary CPUs - in the Xen-specific value written to be later
overwritten with whatever the generic code determines (with no
guarantee that the two values are identical).

Signed-off-by: Jan Beulich <jbeulich@novell.com>
author Keir Fraser <keir.fraser@citrix.com>
date Thu May 14 10:09:15 2009 +0100 (2009-05-14)
parents 831230e53067
children
line source
1 /*
2 * linux/net/sunrpc/timer.c
3 *
4 * Estimate RPC request round trip time.
5 *
6 * Based on packet round-trip and variance estimator algorithms described
7 * in appendix A of "Congestion Avoidance and Control" by Van Jacobson
8 * and Michael J. Karels (ACM Computer Communication Review; Proceedings
9 * of the Sigcomm '88 Symposium in Stanford, CA, August, 1988).
10 *
11 * This RTT estimator is used only for RPC over datagram protocols.
12 *
13 * Copyright (C) 2002 Trond Myklebust <trond.myklebust@fys.uio.no>
14 */
16 #include <asm/param.h>
18 #include <linux/types.h>
19 #include <linux/unistd.h>
21 #include <linux/sunrpc/clnt.h>
22 #include <linux/sunrpc/xprt.h>
23 #include <linux/sunrpc/timer.h>
25 #define RPC_RTO_MAX (60*HZ)
26 #define RPC_RTO_INIT (HZ/5)
27 #define RPC_RTO_MIN (HZ/10)
29 void
30 rpc_init_rtt(struct rpc_rtt *rt, unsigned long timeo)
31 {
32 unsigned long init = 0;
33 unsigned i;
35 rt->timeo = timeo;
37 if (timeo > RPC_RTO_INIT)
38 init = (timeo - RPC_RTO_INIT) << 3;
39 for (i = 0; i < 5; i++) {
40 rt->srtt[i] = init;
41 rt->sdrtt[i] = RPC_RTO_INIT;
42 rt->ntimeouts[i] = 0;
43 }
44 }
46 /*
47 * NB: When computing the smoothed RTT and standard deviation,
48 * be careful not to produce negative intermediate results.
49 */
50 void
51 rpc_update_rtt(struct rpc_rtt *rt, unsigned timer, long m)
52 {
53 long *srtt, *sdrtt;
55 if (timer-- == 0)
56 return;
58 /* jiffies wrapped; ignore this one */
59 if (m < 0)
60 return;
62 if (m == 0)
63 m = 1L;
65 srtt = (long *)&rt->srtt[timer];
66 m -= *srtt >> 3;
67 *srtt += m;
69 if (m < 0)
70 m = -m;
72 sdrtt = (long *)&rt->sdrtt[timer];
73 m -= *sdrtt >> 2;
74 *sdrtt += m;
76 /* Set lower bound on the variance */
77 if (*sdrtt < RPC_RTO_MIN)
78 *sdrtt = RPC_RTO_MIN;
79 }
81 /*
82 * Estimate rto for an nfs rpc sent via. an unreliable datagram.
83 * Use the mean and mean deviation of rtt for the appropriate type of rpc
84 * for the frequent rpcs and a default for the others.
85 * The justification for doing "other" this way is that these rpcs
86 * happen so infrequently that timer est. would probably be stale.
87 * Also, since many of these rpcs are
88 * non-idempotent, a conservative timeout is desired.
89 * getattr, lookup,
90 * read, write, commit - A+4D
91 * other - timeo
92 */
94 unsigned long
95 rpc_calc_rto(struct rpc_rtt *rt, unsigned timer)
96 {
97 unsigned long res;
99 if (timer-- == 0)
100 return rt->timeo;
102 res = ((rt->srtt[timer] + 7) >> 3) + rt->sdrtt[timer];
103 if (res > RPC_RTO_MAX)
104 res = RPC_RTO_MAX;
106 return res;
107 }