2 * Copyright (c) 2015 Cisco and/or its affiliates.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at:
7 * http://www.apache.org/licenses/LICENSE-2.0
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10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
25 #define NUM_POLICE_RESULTS 3
27 // This is the hardware representation of the policer.
28 // To be multithread-safe, the policer is accessed through a spin-lock
29 // on the lock field. (For a policer update operation, 24B needs to be
30 // modified and this would be a challenge to do with atomic instructions.)
31 // The structure is padded so that no other data is put into the same
32 // 64B cache-line. This reduces cache-thrashing between threads.
35 // The HW TSC tick is roughly one CPU clock cycle.
36 // This is shifted to create a larger period, with a goal to be around 50usec.
37 // The period time will vary based on CPU clock speed.
38 // CPU speeds of 1Ghz to 8Ghz are targetted.
39 // The shift amount is a constant 17 bits, resulting in a period between
40 // 16usec (8Ghz CPU) and 131usec (1Ghz CPU).
41 // The token_per_period computation takes into account the clock speed.
43 // The 32-bit bucket/limit supports about 850ms of burst on a 40GE port,
44 // or 340ms on a 100GE port. If a larger burst is configured, then the
45 // programmed value is simply capped at 2^32-1. If we needed to support
46 // more than that, the bucket and limit fields could be expanded.
48 // tokens_per_period should be > 1000 to support 0.1% granularity.
49 // To support lower rates (which would not meet this requirement), the packet
50 // length, bucket, and limit values can be scaled. The scale is a power of 2
51 // so the multiplication can be implemented as a shift. The control plane
52 // computes the shift amount be the largest possible that still supports the
53 // burst size. This makes the rate accuracy as high as possible.
55 // The 64-bit last_update_time supports a 4Ghz CPU without rollover for 100
58 // The lock field should be used for a spin-lock on the struct. Alternatively,
59 // a thread index field is provided so that policed packets may be handed
60 // off to a single worker thread.
62 #define POLICER_TICKS_PER_PERIOD_SHIFT 17
63 #define POLICER_TICKS_PER_PERIOD (1 << POLICER_TICKS_PER_PERIOD_SHIFT)
68 u32 lock; // for exclusive access to the struct
70 u32 single_rate; // 1 = single rate policer, 0 = two rate policer
71 u32 color_aware; // for hierarchical policing
72 u32 scale; // power-of-2 shift amount for lower rates
77 // Fields are marked as 2R if they are only used for a 2-rate policer,
78 // and MOD if they are modified as part of the update operation.
81 u32 cir_tokens_per_period; // # of tokens for each period
82 u32 pir_tokens_per_period; // 2R
85 u32 current_bucket; // MOD
87 u32 extended_bucket; // MOD
89 u64 last_update_time; // MOD
90 u32 thread_index; // Tie policer to a thread, rather than lock
93 } policer_read_response_type_st;
95 static inline policer_result_e
96 vnet_police_packet (policer_read_response_type_st * policer,
98 policer_result_e packet_color, u64 time)
101 u64 current_tokens, extended_tokens;
102 policer_result_e result;
104 // Scale packet length to support a wide range of speeds
105 packet_length = packet_length << policer->scale;
107 // Compute the number of policer periods that have passed since the last
109 n_periods = time - policer->last_update_time;
110 policer->last_update_time = time;
112 // Since there is no background last-update-time adjustment, n_periods
113 // could grow large if the policer is idle for a long time. This could
114 // cause a 64-bit overflow when computing tokens_per_period * num_periods.
115 // It will overflow if log2(n_periods) + log2(tokens_per_period) > 64.
117 // To mitigate this, the policer configuration algorithm insures that
118 // tokens_per_period is less than 2^22, i.e. this is a 22 bit value not
119 // a 32-bit value. Thus overflow will only occur if n_periods > 64-22 or
120 // 42. 2^42 min-sized periods is 16us * 2^42, or 2 years. So this can
121 // rarely occur. If overflow does happen, the only effect will be that
122 // fewer tokens than the max burst will be added to the bucket for this
123 // packet. This constraint on tokens_per_period lets the ucode omit
124 // code to dynamically check for or prevent the overflow.
126 if (policer->single_rate)
129 // Compute number of tokens for this time period
131 policer->current_bucket + n_periods * policer->cir_tokens_per_period;
132 if (current_tokens > policer->current_limit)
134 current_tokens = policer->current_limit;
138 policer->extended_bucket + n_periods * policer->cir_tokens_per_period;
139 if (extended_tokens > policer->extended_limit)
141 extended_tokens = policer->extended_limit;
146 if ((!policer->color_aware || (packet_color == POLICE_CONFORM))
147 && (current_tokens >= packet_length))
149 policer->current_bucket = current_tokens - packet_length;
150 policer->extended_bucket = extended_tokens - packet_length;
151 result = POLICE_CONFORM;
153 else if ((!policer->color_aware || (packet_color != POLICE_VIOLATE))
154 && (extended_tokens >= packet_length))
156 policer->current_bucket = current_tokens;
157 policer->extended_bucket = extended_tokens - packet_length;
158 result = POLICE_EXCEED;
162 policer->current_bucket = current_tokens;
163 policer->extended_bucket = extended_tokens;
164 result = POLICE_VIOLATE;
172 // Compute number of tokens for this time period
174 policer->current_bucket + n_periods * policer->cir_tokens_per_period;
176 policer->extended_bucket + n_periods * policer->pir_tokens_per_period;
177 if (current_tokens > policer->current_limit)
179 current_tokens = policer->current_limit;
181 if (extended_tokens > policer->extended_limit)
183 extended_tokens = policer->extended_limit;
188 if ((policer->color_aware && (packet_color == POLICE_VIOLATE))
189 || (extended_tokens < packet_length))
191 policer->current_bucket = current_tokens;
192 policer->extended_bucket = extended_tokens;
193 result = POLICE_VIOLATE;
195 else if ((policer->color_aware && (packet_color == POLICE_EXCEED))
196 || (current_tokens < packet_length))
198 policer->current_bucket = current_tokens;
199 policer->extended_bucket = extended_tokens - packet_length;
200 result = POLICE_EXCEED;
204 policer->current_bucket = current_tokens - packet_length;
205 policer->extended_bucket = extended_tokens - packet_length;
206 result = POLICE_CONFORM;
212 #endif // __POLICE_H__
215 * fd.io coding-style-patch-verification: ON
218 * eval: (c-set-style "gnu")