diff options
author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /net/sunrpc/timer.c |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'net/sunrpc/timer.c')
-rw-r--r-- | net/sunrpc/timer.c | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/net/sunrpc/timer.c b/net/sunrpc/timer.c new file mode 100644 index 00000000000..bcbdf6430d5 --- /dev/null +++ b/net/sunrpc/timer.c @@ -0,0 +1,107 @@ +/* + * 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> +#include <linux/sunrpc/xprt.h> +#include <linux/sunrpc/timer.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; +} |