Willy Tarreau | 7f062c4 | 2009-03-05 18:43:00 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Event rate calculation functions. |
| 3 | * |
| 4 | * Copyright 2000-2009 Willy Tarreau <w@1wt.eu> |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU General Public License |
| 8 | * as published by the Free Software Foundation; either version |
| 9 | * 2 of the License, or (at your option) any later version. |
| 10 | * |
| 11 | */ |
| 12 | |
| 13 | #include <common/config.h> |
| 14 | #include <common/standard.h> |
| 15 | #include <common/time.h> |
Willy Tarreau | 7958422 | 2009-03-06 09:18:27 +0100 | [diff] [blame^] | 16 | #include <common/tools.h> |
Willy Tarreau | 7f062c4 | 2009-03-05 18:43:00 +0100 | [diff] [blame] | 17 | #include <proto/freq_ctr.h> |
| 18 | |
| 19 | /* Read a frequency counter taking history into account for missing time in |
| 20 | * current period. Current second is sub-divided in 1000 chunks of one ms, |
| 21 | * and the missing ones are read proportionally from previous value. The |
| 22 | * return value has the same precision as one input data sample, so low rates |
| 23 | * will be inaccurate still appropriate for max checking. One trick we use for |
| 24 | * low values is to specially handle the case where the rate is between 0 and 1 |
| 25 | * in order to avoid flapping while waiting for the next event. |
Willy Tarreau | 7958422 | 2009-03-06 09:18:27 +0100 | [diff] [blame^] | 26 | * |
| 27 | * For immediate limit checking, it's recommended to use freq_ctr_remain() and |
| 28 | * next_event_delay() instead which do not have the flapping correction, so |
| 29 | * that even frequencies as low as one event/period are properly handled. |
Willy Tarreau | 7f062c4 | 2009-03-05 18:43:00 +0100 | [diff] [blame] | 30 | */ |
| 31 | unsigned int read_freq_ctr(struct freq_ctr *ctr) |
| 32 | { |
| 33 | unsigned int cur; |
| 34 | if (unlikely(ctr->curr_sec != now.tv_sec)) |
| 35 | rotate_freq_ctr(ctr); |
| 36 | |
| 37 | cur = ctr->curr_ctr; |
| 38 | if (ctr->prev_ctr <= 1 && !ctr->curr_ctr) |
| 39 | return ctr->prev_ctr; /* very low rate, avoid flapping */ |
| 40 | |
| 41 | return cur + mul32hi(ctr->prev_ctr, ~curr_sec_ms_scaled); |
| 42 | } |
| 43 | |
Willy Tarreau | 7958422 | 2009-03-06 09:18:27 +0100 | [diff] [blame^] | 44 | /* returns the number of remaining events that can occur on this freq counter |
| 45 | * while respecting <freq> and taking into account that <pend> events are |
| 46 | * already known to be pending. Returns 0 if limit was reached. |
| 47 | */ |
| 48 | unsigned int freq_ctr_remain(struct freq_ctr *ctr, unsigned int freq, unsigned int pend) |
| 49 | { |
| 50 | unsigned int cur; |
| 51 | if (unlikely(ctr->curr_sec != now.tv_sec)) |
| 52 | rotate_freq_ctr(ctr); |
| 53 | |
| 54 | cur = mul32hi(ctr->prev_ctr, ~curr_sec_ms_scaled); |
| 55 | cur += ctr->curr_ctr + pend; |
| 56 | |
| 57 | if (cur >= freq) |
| 58 | return 0; |
| 59 | return freq - cur; |
| 60 | } |
| 61 | |
| 62 | /* return the expected wait time in ms before the next event may occur, |
| 63 | * respecting frequency <freq>, and assuming there may already be some pending |
| 64 | * events. It returns zero if we can proceed immediately, otherwise the wait |
| 65 | * time, which will be rounded down 1ms for better accuracy, with a minimum |
| 66 | * of one ms. |
| 67 | */ |
| 68 | unsigned int next_event_delay(struct freq_ctr *ctr, unsigned int freq, unsigned int pend) |
| 69 | { |
| 70 | unsigned int cur, wait; |
| 71 | |
| 72 | if (unlikely(ctr->curr_sec != now.tv_sec)) |
| 73 | rotate_freq_ctr(ctr); |
| 74 | |
| 75 | cur = mul32hi(ctr->prev_ctr, ~curr_sec_ms_scaled); |
| 76 | cur += ctr->curr_ctr + pend; |
| 77 | |
| 78 | if (cur < freq) |
| 79 | return 0; |
| 80 | |
| 81 | wait = 999 / cur; |
| 82 | return MAX(wait, 1); |
| 83 | } |
| 84 | |
Willy Tarreau | 7f062c4 | 2009-03-05 18:43:00 +0100 | [diff] [blame] | 85 | |
| 86 | /* |
| 87 | * Local variables: |
| 88 | * c-indent-level: 8 |
| 89 | * c-basic-offset: 8 |
| 90 | * End: |
| 91 | */ |