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/*
* Copyright (c) 2015 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef __POLICE_H__
#define __POLICE_H__
typedef enum
{
POLICE_CONFORM = 0,
POLICE_EXCEED = 1,
POLICE_VIOLATE = 2,
} policer_result_e;
// This is the hardware representation of the policer.
// To be multithread-safe, the policer is accessed through a spin-lock
// on the lock field. (For a policer update operation, 24B needs to be
// modified and this would be a challenge to do with atomic instructions.)
// The structure is padded so that no other data is put into the same
// 64B cache-line. This reduces cache-thrashing between threads.
//
// A note on scale:
// The HW TSC tick is roughly one CPU clock cycle.
// This is shifted to create a larger period, with a goal to be around 50usec.
// The period time will vary based on CPU clock speed.
// CPU speeds of 1Ghz to 8Ghz are targetted.
// The shift amount is a constant 17 bits, resulting in a period between
// 16usec (8Ghz CPU) and 131usec (1Ghz CPU).
// The token_per_period computation takes into account the clock speed.
//
// The 32-bit bucket/limit supports about 850ms of burst on a 40GE port,
// or 340ms on a 100GE port. If a larger burst is configued, then the
// programmed value is simply capped at 2^32-1. If we needed to support
// more than that, the bucket and limit fields could be expanded.
//
// tokens_per_period should be > 1000 to support 0.1% granularity.
// To support lower rates (which would not meet this requirement), the packet
// length, bucket, and limit values can be scaled. The scale is a power of 2
// so the multiplication can be implemented as a shift. The control plane
// computes the shift amount be the largest possible that still supports the
// burst size. This makes the rate accuracy as high as possible.
//
// The 64-bit last_update_time supports a 4Ghz CPU without rollover for 100 years
//
// The lock field should be used for a spin-lock on the struct.
#define POLICER_TICKS_PER_PERIOD_SHIFT 17
#define POLICER_TICKS_PER_PERIOD (1 << POLICER_TICKS_PER_PERIOD_SHIFT)
typedef struct
{
u32 lock; // for exclusive access to the struct
u32 single_rate; // 1 = single rate policer, 0 = two rate policer
u32 color_aware; // for hierarchical policing
u32 scale; // power-of-2 shift amount for lower rates
u8 action[3];
u8 mark_dscp[3];
u8 pad[2];
// Fields are marked as 2R if they are only used for a 2-rate policer,
// and MOD if they are modified as part of the update operation.
// 1 token = 1 byte.
u32 cir_tokens_per_period; // # of tokens for each period
u32 pir_tokens_per_period; // 2R
u32 current_limit;
u32 current_bucket; // MOD
u32 extended_limit;
u32 extended_bucket; // MOD
u64 last_update_time; // MOD
u64 pad64;
} policer_read_response_type_st;
static inline policer_result_e
vnet_police_packet (policer_read_response_type_st * policer,
u32 packet_length,
policer_result_e packet_color, u64 time)
{
u64 n_periods;
u64 current_tokens, extended_tokens;
policer_result_e result;
// Scale packet length to support a wide range of speeds
packet_length = packet_length << policer->scale;
// Compute the number of policer periods that have passed since the last
// operation.
n_periods = time - policer->last_update_time;
policer->last_update_time = time;
// Since there is no background last-update-time adjustment, n_periods
// could grow large if the policer is idle for a long time. This could
// cause a 64-bit overflow when computing tokens_per_period * num_periods.
// It will overflow if log2(n_periods) + log2(tokens_per_period) > 64.
//
// To mitigate this, the policer configuration algorithm insures that
// tokens_per_period is less than 2^22, i.e. this is a 22 bit value not
// a 32-bit value. Thus overflow will only occur if n_periods > 64-22 or
// 42. 2^42 min-sized periods is 16us * 2^42, or 2 years. So this can
// rarely occur. If overflow does happen, the only effect will be that
// fewer tokens than the max burst will be added to the bucket for this
// packet. This constraint on tokens_per_period lets the ucode omit
// code to dynamically check for or prevent the overflow.
if (policer->single_rate)
{
// Compute number of tokens for this time period
current_tokens =
policer->current_bucket + n_periods * policer->cir_tokens_per_period;
if (current_tokens > policer->current_limit)
{
current_tokens = policer->current_limit;
}
extended_tokens =
policer->extended_bucket + n_periods * policer->cir_tokens_per_period;
if (extended_tokens > policer->extended_limit)
{
extended_tokens = policer->extended_limit;
}
// Determine color
if ((!policer->color_aware || (packet_color == POLICE_CONFORM))
&& (current_tokens >= packet_length))
{
policer->current_bucket = current_tokens - packet_length;
policer->extended_bucket = extended_tokens - packet_length;
result = POLICE_CONFORM;
}
else if ((!policer->color_aware || (packet_color != POLICE_VIOLATE))
&& (extended_tokens >= packet_length))
{
policer->current_bucket = current_tokens;
policer->extended_bucket = extended_tokens - packet_length;
result = POLICE_EXCEED;
}
else
{
policer->current_bucket = current_tokens;
policer->extended_bucket = extended_tokens;
result = POLICE_VIOLATE;
}
}
else
{
// Two-rate policer
// Compute number of tokens for this time period
current_tokens =
policer->current_bucket + n_periods * policer->cir_tokens_per_period;
extended_tokens =
policer->extended_bucket + n_periods * policer->pir_tokens_per_period;
if (current_tokens > policer->current_limit)
{
current_tokens = policer->current_limit;
}
if (extended_tokens > policer->extended_limit)
{
extended_tokens = policer->extended_limit;
}
// Determine color
if ((policer->color_aware && (packet_color == POLICE_VIOLATE))
|| (extended_tokens < packet_length))
{
policer->current_bucket = current_tokens;
policer->extended_bucket = extended_tokens;
result = POLICE_VIOLATE;
}
else if ((policer->color_aware && (packet_color == POLICE_EXCEED))
|| (current_tokens < packet_length))
{
policer->current_bucket = current_tokens;
policer->extended_bucket = extended_tokens - packet_length;
result = POLICE_EXCEED;
}
else
{
policer->current_bucket = current_tokens - packet_length;
policer->extended_bucket = extended_tokens - packet_length;
result = POLICE_CONFORM;
}
}
return result;
}
#endif // __POLICE_H__
/*
* fd.io coding-style-patch-verification: ON
*
* Local Variables:
* eval: (c-set-style "gnu")
* End:
*/
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