Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | */ |
| 15 | |
| 16 | #include <asm/param.h> |
| 17 | |
| 18 | #include <linux/types.h> |
| 19 | #include <linux/unistd.h> |
\"Talpey, Thomas\ | 1244480 | 2007-09-10 13:45:36 -0400 | [diff] [blame] | 20 | #include <linux/module.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 21 | |
| 22 | #include <linux/sunrpc/clnt.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 23 | |
| 24 | #define RPC_RTO_MAX (60*HZ) |
| 25 | #define RPC_RTO_INIT (HZ/5) |
| 26 | #define RPC_RTO_MIN (HZ/10) |
| 27 | |
Chuck Lever | c05988c | 2009-08-09 15:09:47 -0400 | [diff] [blame] | 28 | /** |
| 29 | * rpc_init_rtt - Initialize an RPC RTT estimator context |
| 30 | * @rt: context to initialize |
| 31 | * @timeo: initial timeout value, in jiffies |
| 32 | * |
| 33 | */ |
| 34 | void rpc_init_rtt(struct rpc_rtt *rt, unsigned long timeo) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 35 | { |
| 36 | unsigned long init = 0; |
Eric Dumazet | 95c9617 | 2012-04-15 05:58:06 +0000 | [diff] [blame] | 37 | unsigned int i; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 38 | |
| 39 | rt->timeo = timeo; |
| 40 | |
| 41 | if (timeo > RPC_RTO_INIT) |
| 42 | init = (timeo - RPC_RTO_INIT) << 3; |
| 43 | for (i = 0; i < 5; i++) { |
| 44 | rt->srtt[i] = init; |
| 45 | rt->sdrtt[i] = RPC_RTO_INIT; |
| 46 | rt->ntimeouts[i] = 0; |
| 47 | } |
| 48 | } |
\"Talpey, Thomas\ | 1244480 | 2007-09-10 13:45:36 -0400 | [diff] [blame] | 49 | EXPORT_SYMBOL_GPL(rpc_init_rtt); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 50 | |
Chuck Lever | c05988c | 2009-08-09 15:09:47 -0400 | [diff] [blame] | 51 | /** |
| 52 | * rpc_update_rtt - Update an RPC RTT estimator context |
| 53 | * @rt: context to update |
| 54 | * @timer: timer array index (request type) |
| 55 | * @m: recent actual RTT, in jiffies |
| 56 | * |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 57 | * NB: When computing the smoothed RTT and standard deviation, |
| 58 | * be careful not to produce negative intermediate results. |
| 59 | */ |
Eric Dumazet | 95c9617 | 2012-04-15 05:58:06 +0000 | [diff] [blame] | 60 | void rpc_update_rtt(struct rpc_rtt *rt, unsigned int timer, long m) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 61 | { |
| 62 | long *srtt, *sdrtt; |
| 63 | |
| 64 | if (timer-- == 0) |
| 65 | return; |
| 66 | |
| 67 | /* jiffies wrapped; ignore this one */ |
| 68 | if (m < 0) |
| 69 | return; |
| 70 | |
| 71 | if (m == 0) |
| 72 | m = 1L; |
| 73 | |
| 74 | srtt = (long *)&rt->srtt[timer]; |
| 75 | m -= *srtt >> 3; |
| 76 | *srtt += m; |
| 77 | |
| 78 | if (m < 0) |
| 79 | m = -m; |
| 80 | |
| 81 | sdrtt = (long *)&rt->sdrtt[timer]; |
| 82 | m -= *sdrtt >> 2; |
| 83 | *sdrtt += m; |
| 84 | |
| 85 | /* Set lower bound on the variance */ |
| 86 | if (*sdrtt < RPC_RTO_MIN) |
| 87 | *sdrtt = RPC_RTO_MIN; |
| 88 | } |
\"Talpey, Thomas\ | 1244480 | 2007-09-10 13:45:36 -0400 | [diff] [blame] | 89 | EXPORT_SYMBOL_GPL(rpc_update_rtt); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 90 | |
Chuck Lever | c05988c | 2009-08-09 15:09:47 -0400 | [diff] [blame] | 91 | /** |
| 92 | * rpc_calc_rto - Provide an estimated timeout value |
| 93 | * @rt: context to use for calculation |
| 94 | * @timer: timer array index (request type) |
| 95 | * |
| 96 | * Estimate RTO for an NFS RPC sent via an unreliable datagram. Use |
| 97 | * the mean and mean deviation of RTT for the appropriate type of RPC |
| 98 | * for frequently issued RPCs, and a fixed default for the others. |
| 99 | * |
| 100 | * The justification for doing "other" this way is that these RPCs |
| 101 | * happen so infrequently that timer estimation would probably be |
| 102 | * stale. Also, since many of these RPCs are non-idempotent, a |
| 103 | * conservative timeout is desired. |
| 104 | * |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 105 | * getattr, lookup, |
| 106 | * read, write, commit - A+4D |
| 107 | * other - timeo |
| 108 | */ |
Eric Dumazet | 95c9617 | 2012-04-15 05:58:06 +0000 | [diff] [blame] | 109 | unsigned long rpc_calc_rto(struct rpc_rtt *rt, unsigned int timer) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 110 | { |
| 111 | unsigned long res; |
| 112 | |
| 113 | if (timer-- == 0) |
| 114 | return rt->timeo; |
| 115 | |
| 116 | res = ((rt->srtt[timer] + 7) >> 3) + rt->sdrtt[timer]; |
| 117 | if (res > RPC_RTO_MAX) |
| 118 | res = RPC_RTO_MAX; |
| 119 | |
| 120 | return res; |
| 121 | } |
\"Talpey, Thomas\ | 1244480 | 2007-09-10 13:45:36 -0400 | [diff] [blame] | 122 | EXPORT_SYMBOL_GPL(rpc_calc_rto); |