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,
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12 * See the License for the specific language governing permissions and
13 * limitations under the License.
25 #define NUM_POLICE_RESULTS 3
31 QOS_ACTION_MARK_AND_TRANSMIT,
33 } __clib_packed qos_action_type_en;
35 // This is the hardware representation of the policer.
36 // To be multithread-safe, the policer is accessed through a spin-lock
37 // on the lock field. (For a policer update operation, 24B needs to be
38 // modified and this would be a challenge to do with atomic instructions.)
39 // The structure is padded so that no other data is put into the same
40 // 64B cache-line. This reduces cache-thrashing between threads.
43 // The HW TSC tick is roughly one CPU clock cycle.
44 // This is shifted to create a larger period, with a goal to be around 50usec.
45 // The period time will vary based on CPU clock speed.
46 // CPU speeds of 1Ghz to 8Ghz are targetted.
47 // The shift amount is a constant 17 bits, resulting in a period between
48 // 16usec (8Ghz CPU) and 131usec (1Ghz CPU).
49 // The token_per_period computation takes into account the clock speed.
51 // The 32-bit bucket/limit supports about 850ms of burst on a 40GE port,
52 // or 340ms on a 100GE port. If a larger burst is configured, then the
53 // programmed value is simply capped at 2^32-1. If we needed to support
54 // more than that, the bucket and limit fields could be expanded.
56 // tokens_per_period should be > 1000 to support 0.1% granularity.
57 // To support lower rates (which would not meet this requirement), the packet
58 // length, bucket, and limit values can be scaled. The scale is a power of 2
59 // so the multiplication can be implemented as a shift. The control plane
60 // computes the shift amount be the largest possible that still supports the
61 // burst size. This makes the rate accuracy as high as possible.
63 // The 64-bit last_update_time supports a 4Ghz CPU without rollover for 100
66 // The lock field should be used for a spin-lock on the struct. Alternatively,
67 // a thread index field is provided so that policed packets may be handed
68 // off to a single worker thread.
70 #define POLICER_TICKS_PER_PERIOD_SHIFT 17
71 #define POLICER_TICKS_PER_PERIOD (1 << POLICER_TICKS_PER_PERIOD_SHIFT)
75 CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
76 u32 lock; // for exclusive access to the struct
78 u32 single_rate; // 1 = single rate policer, 0 = two rate policer
79 u32 color_aware; // for hierarchical policing
80 u32 scale; // power-of-2 shift amount for lower rates
81 qos_action_type_en action[3];
82 ip_dscp_t mark_dscp[3];
85 // Fields are marked as 2R if they are only used for a 2-rate policer,
86 // and MOD if they are modified as part of the update operation.
89 u32 cir_tokens_per_period; // # of tokens for each period
90 u32 pir_tokens_per_period; // 2R
93 u32 current_bucket; // MOD
95 u32 extended_bucket; // MOD
97 u64 last_update_time; // MOD
98 u32 thread_index; // Tie policer to a thread, rather than lock
103 STATIC_ASSERT_SIZEOF (policer_t, CLIB_CACHE_LINE_BYTES);
105 static inline policer_result_e
106 vnet_police_packet (policer_t *policer, u32 packet_length,
107 policer_result_e packet_color, u64 time)
110 u64 current_tokens, extended_tokens;
111 policer_result_e result;
113 // Scale packet length to support a wide range of speeds
114 packet_length = packet_length << policer->scale;
116 // Compute the number of policer periods that have passed since the last
118 n_periods = time - policer->last_update_time;
119 policer->last_update_time = time;
121 // Since there is no background last-update-time adjustment, n_periods
122 // could grow large if the policer is idle for a long time. This could
123 // cause a 64-bit overflow when computing tokens_per_period * num_periods.
124 // It will overflow if log2(n_periods) + log2(tokens_per_period) > 64.
126 // To mitigate this, the policer configuration algorithm insures that
127 // tokens_per_period is less than 2^22, i.e. this is a 22 bit value not
128 // a 32-bit value. Thus overflow will only occur if n_periods > 64-22 or
129 // 42. 2^42 min-sized periods is 16us * 2^42, or 2 years. So this can
130 // rarely occur. If overflow does happen, the only effect will be that
131 // fewer tokens than the max burst will be added to the bucket for this
132 // packet. This constraint on tokens_per_period lets the ucode omit
133 // code to dynamically check for or prevent the overflow.
135 if (policer->single_rate)
138 // Compute number of tokens for this time period
140 policer->current_bucket + n_periods * policer->cir_tokens_per_period;
141 if (current_tokens > policer->current_limit)
143 current_tokens = policer->current_limit;
147 policer->extended_bucket + n_periods * policer->cir_tokens_per_period;
148 if (extended_tokens > policer->extended_limit)
150 extended_tokens = policer->extended_limit;
155 if ((!policer->color_aware || (packet_color == POLICE_CONFORM))
156 && (current_tokens >= packet_length))
158 policer->current_bucket = current_tokens - packet_length;
159 policer->extended_bucket = extended_tokens - packet_length;
160 result = POLICE_CONFORM;
162 else if ((!policer->color_aware || (packet_color != POLICE_VIOLATE))
163 && (extended_tokens >= packet_length))
165 policer->current_bucket = current_tokens;
166 policer->extended_bucket = extended_tokens - packet_length;
167 result = POLICE_EXCEED;
171 policer->current_bucket = current_tokens;
172 policer->extended_bucket = extended_tokens;
173 result = POLICE_VIOLATE;
181 // Compute number of tokens for this time period
183 policer->current_bucket + n_periods * policer->cir_tokens_per_period;
185 policer->extended_bucket + n_periods * policer->pir_tokens_per_period;
186 if (current_tokens > policer->current_limit)
188 current_tokens = policer->current_limit;
190 if (extended_tokens > policer->extended_limit)
192 extended_tokens = policer->extended_limit;
197 if ((policer->color_aware && (packet_color == POLICE_VIOLATE))
198 || (extended_tokens < packet_length))
200 policer->current_bucket = current_tokens;
201 policer->extended_bucket = extended_tokens;
202 result = POLICE_VIOLATE;
204 else if ((policer->color_aware && (packet_color == POLICE_EXCEED))
205 || (current_tokens < packet_length))
207 policer->current_bucket = current_tokens;
208 policer->extended_bucket = extended_tokens - packet_length;
209 result = POLICE_EXCEED;
213 policer->current_bucket = current_tokens - packet_length;
214 policer->extended_bucket = extended_tokens - packet_length;
215 result = POLICE_CONFORM;
221 #endif // __POLICE_H__
224 * fd.io coding-style-patch-verification: ON
227 * eval: (c-set-style "gnu")