Add a new token-bucket backend abstraction, with tests
This differs from our previous token bucket abstraction in a few
ways:
1) It is an abstraction, and not a collection of fields.
2) It is meant to be used with monotonic timestamps, which should
produce better results than calling gettimeofday over and over.
This commit is contained in:
Nick Mathewson
parent
d8ef9a2d1e
commit
c376200f6a
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@ -97,6 +97,7 @@ LIBOR_A_SRC = \
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src/common/util_process.c \
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src/common/sandbox.c \
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src/common/storagedir.c \
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src/common/token_bucket.c \
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src/common/workqueue.c \
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$(libor_extra_source) \
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$(threads_impl_source) \
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@ -184,6 +185,7 @@ COMMONHEADERS = \
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src/common/storagedir.h \
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src/common/testsupport.h \
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src/common/timers.h \
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src/common/token_bucket.h \
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src/common/torint.h \
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src/common/torlog.h \
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src/common/tortls.h \
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@ -0,0 +1,180 @@
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/* Copyright (c) 2018, The Tor Project, Inc. */
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/* See LICENSE for licensing information */
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/**
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* \file token_bucket.c
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* \brief Functions to use and manipulate token buckets, used for
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* rate-limiting on connections and globally.
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*
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* Tor uses these token buckets to keep track of bandwidth usage, and
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* sometimes other things too.
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*
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* The time units we use internally are based on "timestamp" units -- see
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* monotime_coarse_to_stamp() for a rationale.
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*
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* Token buckets may become negative.
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**/
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#define TOKEN_BUCKET_PRIVATE
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#include "token_bucket.h"
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#include "util_bug.h"
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/** Convert a rate in bytes per second to a rate in bytes per step */
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static uint32_t
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rate_per_sec_to_rate_per_step(uint32_t rate)
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{
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/*
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The precise calculation we'd want to do is
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(rate / 1000) * to_approximate_msec(TICKS_PER_STEP). But to minimize
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rounding error, we do it this way instead, and divide last.
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*/
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return (uint32_t)
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monotime_coarse_stamp_units_to_approx_msec(rate*TICKS_PER_STEP)/1000;
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}
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/**
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* Initialize a token bucket in *<b>bucket</b>, set up to allow <b>rate</b>
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* bytes per second, with a maximum burst of <b>burst</b> bytes. The bucket
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* is created such that <b>now_ts</b> is the current timestamp. The bucket
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* starts out full.
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*/
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void
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token_bucket_init(token_bucket_t *bucket,
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uint32_t rate,
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uint32_t burst,
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uint32_t now_ts)
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{
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memset(bucket, 0, sizeof(token_bucket_t));
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token_bucket_adjust(bucket, rate, burst);
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token_bucket_reset(bucket, now_ts);
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}
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/**
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* Change the configured rate (in bytes per second) and burst (in bytes)
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* for the token bucket in *<b>bucket</b>.
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*/
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void
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token_bucket_adjust(token_bucket_t *bucket,
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uint32_t rate,
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uint32_t burst)
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{
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tor_assert_nonfatal(rate > 0);
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tor_assert_nonfatal(burst > 0);
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if (burst > TOKEN_BUCKET_MAX_BURST)
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burst = TOKEN_BUCKET_MAX_BURST;
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bucket->rate = rate_per_sec_to_rate_per_step(rate);
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bucket->burst = burst;
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bucket->read_bucket = MIN(bucket->read_bucket, (int32_t)burst);
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bucket->write_bucket = MIN(bucket->write_bucket, (int32_t)burst);
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}
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/**
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* Reset <b>bucket</b> to be full, as of timestamp <b>now_ts</b>.
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*/
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void
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token_bucket_reset(token_bucket_t *bucket,
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uint32_t now_ts)
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{
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bucket->read_bucket = bucket->burst;
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bucket->write_bucket = bucket->burst;
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bucket->last_refilled_at_ts = now_ts;
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}
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/* Helper: see token_bucket_refill */
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static int
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refill_single_bucket(int32_t *bucketptr,
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const uint32_t rate,
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const int32_t burst,
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const uint32_t elapsed_steps)
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{
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const int was_empty = (*bucketptr <= 0);
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/* The casts here prevent an underflow.
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*
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* Note that even if the bucket value is negative, subtracting it from
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* "burst" will still produce a correct result. If this result is
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* ridiculously high, then the "elapsed_steps > gap / rate" check below
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* should catch it. */
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const size_t gap = ((size_t)burst) - ((size_t)*bucketptr);
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if (elapsed_steps > gap / rate) {
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*bucketptr = burst;
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} else {
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*bucketptr += rate * elapsed_steps;
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}
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return was_empty && *bucketptr > 0;
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}
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/**
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* Refill <b>bucket</b> as appropriate, given that the current timestamp
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* is <b>now_ts</b>.
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*
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* Return a bitmask containing TB_READ iff read bucket was empty and became
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* nonempty, and TB_WRITE iff the write bucket was empty and became nonempty.
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*/
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int
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token_bucket_refill(token_bucket_t *bucket,
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uint32_t now_ts)
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{
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const uint32_t elapsed_ticks = (now_ts - bucket->last_refilled_at_ts);
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const uint32_t elapsed_steps = elapsed_ticks / TICKS_PER_STEP;
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if (!elapsed_steps) {
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/* Note that if less than one whole step elapsed, we don't advance the
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* time in last_refilled_at_ts. That's intentional: we want to make sure
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* that we add some bytes to it eventually. */
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return 0;
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}
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int flags = 0;
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if (refill_single_bucket(&bucket->read_bucket,
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bucket->rate, bucket->burst, elapsed_steps))
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flags |= TB_READ;
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if (refill_single_bucket(&bucket->write_bucket,
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bucket->rate, bucket->burst, elapsed_steps))
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flags |= TB_WRITE;
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bucket->last_refilled_at_ts = now_ts;
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return flags;
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}
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static int
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decrement_single_bucket(int32_t *bucketptr,
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ssize_t n)
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{
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if (BUG(n < 0))
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return 0;
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const int becomes_empty = *bucketptr > 0 && n >= *bucketptr;
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*bucketptr -= n;
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return becomes_empty;
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}
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/**
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* Decrement the read token bucket in <b>bucket</b> by <b>n</b> bytes.
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*
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* Return true if the bucket was nonempty and became empty; return false
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* otherwise.
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*/
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int
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token_bucket_dec_read(token_bucket_t *bucket,
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ssize_t n)
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{
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return decrement_single_bucket(&bucket->read_bucket, n);
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}
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/**
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* Decrement the write token bucket in <b>bucket</b> by <b>n</b> bytes.
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*
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* Return true if the bucket was nonempty and became empty; return false
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* otherwise.
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*/
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int
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token_bucket_dec_write(token_bucket_t *bucket,
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ssize_t n)
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{
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return decrement_single_bucket(&bucket->write_bucket, n);
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}
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@ -0,0 +1,72 @@
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/* Copyright (c) 2018, The Tor Project, Inc. */
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/* See LICENSE for licensing information */
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/**
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* \file token_bucket.h
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* \brief Headers for token_bucket.c
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**/
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#ifndef TOR_TOKEN_BUCKET_H
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#define TOR_TOKEN_BUCKET_H
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#include "torint.h"
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typedef struct token_bucket_t {
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uint32_t rate;
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int32_t burst;
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int32_t read_bucket;
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int32_t write_bucket;
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uint32_t last_refilled_at_ts;
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} token_bucket_t;
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#define TOKEN_BUCKET_MAX_BURST INT32_MAX
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void token_bucket_init(token_bucket_t *bucket,
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uint32_t rate,
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uint32_t burst,
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uint32_t now_ts);
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void token_bucket_adjust(token_bucket_t *bucket,
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uint32_t rate, uint32_t burst);
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void token_bucket_reset(token_bucket_t *bucket,
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uint32_t now_ts);
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#define TB_READ 1
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#define TB_WRITE 2
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int token_bucket_refill(token_bucket_t *bucket,
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uint32_t now_ts);
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int token_bucket_dec_read(token_bucket_t *bucket,
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ssize_t n);
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int token_bucket_dec_write(token_bucket_t *bucket,
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ssize_t n);
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static inline size_t token_bucket_get_read(const token_bucket_t *bucket);
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static inline size_t
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token_bucket_get_read(const token_bucket_t *bucket)
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{
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const ssize_t b = bucket->read_bucket;
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return b >= 0 ? b : 0;
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}
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static inline size_t token_bucket_get_write(const token_bucket_t *bucket);
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static inline size_t
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token_bucket_get_write(const token_bucket_t *bucket)
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{
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const ssize_t b = bucket->write_bucket;
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return b >= 0 ? b : 0;
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}
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#ifdef TOKEN_BUCKET_PRIVATE
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/* To avoid making the rates too small, we consider units of "steps",
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* where a "step" is defined as this many timestamp ticks. Keep this
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* a power of two if you can. */
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#define TICKS_PER_STEP 16
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#endif
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#endif /* TOR_TOKEN_BUCKET_H */
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@ -89,6 +89,7 @@ src_test_test_SOURCES = \
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src/test/test_address.c \
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src/test/test_address_set.c \
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src/test/test_buffers.c \
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src/test/test_bwmgt.c \
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src/test/test_cell_formats.c \
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src/test/test_cell_queue.c \
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src/test/test_channel.c \
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@ -812,6 +812,7 @@ struct testgroup_t testgroups[] = {
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{ "address/", address_tests },
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{ "address_set/", address_set_tests },
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{ "buffer/", buffer_tests },
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{ "bwmgt/", bwmgt_tests },
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{ "cellfmt/", cell_format_tests },
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{ "cellqueue/", cell_queue_tests },
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{ "channel/", channel_tests },
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@ -178,6 +178,7 @@ extern struct testcase_t accounting_tests[];
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extern struct testcase_t addr_tests[];
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extern struct testcase_t address_tests[];
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extern struct testcase_t address_set_tests[];
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extern struct testcase_t bwmgt_tests[];
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extern struct testcase_t buffer_tests[];
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extern struct testcase_t cell_format_tests[];
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extern struct testcase_t cell_queue_tests[];
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@ -0,0 +1,199 @@
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/* Copyright (c) 2018, The Tor Project, Inc. */
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/* See LICENSE for licensing information */
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/**
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* \file test_bwmgt.c
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* \brief tests for bandwidth management / token bucket functions
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*/
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#define TOKEN_BUCKET_PRIVATE
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#include "or.h"
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#include "test.h"
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#include "token_bucket.h"
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// an imaginary time, in timestamp units. Chosen so it will roll over.
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static const uint32_t START_TS = UINT32_MAX-10;
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static const int32_t KB = 1024;
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static void
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test_bwmgt_token_buf_init(void *arg)
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{
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(void)arg;
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token_bucket_t b;
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token_bucket_init(&b, 16*KB, 64*KB, START_TS);
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// Burst is correct
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tt_uint_op(b.burst, OP_EQ, 64*KB);
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// Rate is correct, within 1 percent.
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{
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uint32_t ticks_per_sec =
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(uint32_t) monotime_msec_to_approx_coarse_stamp_units(1000);
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uint32_t rate_per_sec = (b.rate * ticks_per_sec / TICKS_PER_STEP);
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tt_uint_op(rate_per_sec, OP_GT, 16*KB-160);
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tt_uint_op(rate_per_sec, OP_LT, 16*KB+160);
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}
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// Bucket starts out full:
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tt_uint_op(b.last_refilled_at_ts, OP_EQ, START_TS);
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tt_int_op(b.read_bucket, OP_EQ, 64*KB);
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done:
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;
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}
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static void
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test_bwmgt_token_buf_adjust(void *arg)
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{
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(void)arg;
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token_bucket_t b;
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token_bucket_init(&b, 16*KB, 64*KB, START_TS);
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uint32_t rate_orig = b.rate;
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// Increasing burst
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token_bucket_adjust(&b, 16*KB, 128*KB);
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tt_uint_op(b.rate, OP_EQ, rate_orig);
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tt_uint_op(b.read_bucket, OP_EQ, 64*KB);
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tt_uint_op(b.burst, OP_EQ, 128*KB);
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// Decreasing burst but staying above bucket
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token_bucket_adjust(&b, 16*KB, 96*KB);
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tt_uint_op(b.rate, OP_EQ, rate_orig);
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tt_uint_op(b.read_bucket, OP_EQ, 64*KB);
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tt_uint_op(b.burst, OP_EQ, 96*KB);
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// Decreasing burst below bucket,
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token_bucket_adjust(&b, 16*KB, 48*KB);
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tt_uint_op(b.rate, OP_EQ, rate_orig);
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tt_uint_op(b.read_bucket, OP_EQ, 48*KB);
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tt_uint_op(b.burst, OP_EQ, 48*KB);
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// Changing rate.
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token_bucket_adjust(&b, 32*KB, 48*KB);
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tt_uint_op(b.rate, OP_GE, rate_orig*2 - 10);
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tt_uint_op(b.rate, OP_LE, rate_orig*2 + 10);
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tt_uint_op(b.read_bucket, OP_EQ, 48*KB);
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tt_uint_op(b.burst, OP_EQ, 48*KB);
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done:
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;
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}
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static void
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test_bwmgt_token_buf_dec(void *arg)
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{
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(void)arg;
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token_bucket_t b;
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token_bucket_init(&b, 16*KB, 64*KB, START_TS);
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// full-to-not-full.
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tt_int_op(0, OP_EQ, token_bucket_dec_read(&b, KB));
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tt_int_op(b.read_bucket, OP_EQ, 63*KB);
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// Full to almost-not-full
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tt_int_op(0, OP_EQ, token_bucket_dec_read(&b, 63*KB - 1));
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tt_int_op(b.read_bucket, OP_EQ, 1);
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// almost-not-full to empty.
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tt_int_op(1, OP_EQ, token_bucket_dec_read(&b, 1));
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tt_int_op(b.read_bucket, OP_EQ, 0);
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// reset bucket, try full-to-empty
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token_bucket_init(&b, 16*KB, 64*KB, START_TS);
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tt_int_op(1, OP_EQ, token_bucket_dec_read(&b, 64*KB));
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tt_int_op(b.read_bucket, OP_EQ, 0);
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// reset bucket, try underflow.
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token_bucket_init(&b, 16*KB, 64*KB, START_TS);
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tt_int_op(1, OP_EQ, token_bucket_dec_read(&b, 64*KB + 1));
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tt_int_op(b.read_bucket, OP_EQ, -1);
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// A second underflow does not make the bucket empty.
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tt_int_op(0, OP_EQ, token_bucket_dec_read(&b, 1000));
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tt_int_op(b.read_bucket, OP_EQ, -1001);
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done:
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;
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}
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static void
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test_bwmgt_token_buf_refill(void *arg)
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{
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(void)arg;
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token_bucket_t b;
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const uint32_t SEC =
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(uint32_t)monotime_msec_to_approx_coarse_stamp_units(1000);
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token_bucket_init(&b, 16*KB, 64*KB, START_TS);
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/* Make the buffer much emptier, then let one second elapse. */
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token_bucket_dec_read(&b, 48*KB);
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tt_int_op(b.read_bucket, OP_EQ, 16*KB);
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tt_int_op(0, OP_EQ, token_bucket_refill(&b, START_TS + SEC));
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tt_int_op(b.read_bucket, OP_GT, 32*KB - 300);
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tt_int_op(b.read_bucket, OP_LT, 32*KB + 300);
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/* Another half second. */
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tt_int_op(0, OP_EQ, token_bucket_refill(&b, START_TS + SEC*3/2));
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tt_int_op(b.read_bucket, OP_GT, 40*KB - 400);
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tt_int_op(b.read_bucket, OP_LT, 40*KB + 400);
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tt_uint_op(b.last_refilled_at_ts, OP_EQ, START_TS + SEC*3/2);
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/* No time: nothing happens. */
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{
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const uint32_t bucket_orig = b.read_bucket;
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tt_int_op(0, OP_EQ, token_bucket_refill(&b, START_TS + SEC*3/2));
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tt_int_op(b.read_bucket, OP_EQ, bucket_orig);
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}
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/* Another 30 seconds: fill the bucket. */
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tt_int_op(0, OP_EQ, token_bucket_refill(&b, START_TS + SEC*3/2 + SEC*30));
|
||||
tt_int_op(b.read_bucket, OP_EQ, b.burst);
|
||||
tt_uint_op(b.last_refilled_at_ts, OP_EQ, START_TS + SEC*3/2 + SEC*30);
|
||||
|
||||
/* Another 30 seconds: nothing happens. */
|
||||
tt_int_op(0, OP_EQ, token_bucket_refill(&b, START_TS + SEC*3/2 + SEC*60));
|
||||
tt_int_op(b.read_bucket, OP_EQ, b.burst);
|
||||
tt_uint_op(b.last_refilled_at_ts, OP_EQ, START_TS + SEC*3/2 + SEC*60);
|
||||
|
||||
/* Empty the bucket, let two seconds pass, and make sure that a refill is
|
||||
* noticed. */
|
||||
tt_int_op(1, OP_EQ, token_bucket_dec_read(&b, b.burst));
|
||||
tt_int_op(0, OP_EQ, b.read_bucket);
|
||||
tt_int_op(1, OP_EQ, token_bucket_refill(&b, START_TS + SEC*3/2 + SEC*61));
|
||||
tt_int_op(0, OP_EQ, token_bucket_refill(&b, START_TS + SEC*3/2 + SEC*62));
|
||||
tt_int_op(b.read_bucket, OP_GT, 32*KB-300);
|
||||
tt_int_op(b.read_bucket, OP_LT, 32*KB+300);
|
||||
|
||||
/* Underflow the bucket, make sure we detect when it has tokens again. */
|
||||
tt_int_op(1, OP_EQ, token_bucket_dec_read(&b, b.read_bucket+16*KB));
|
||||
tt_int_op(-16*KB, OP_EQ, b.read_bucket);
|
||||
// half a second passes...
|
||||
tt_int_op(0, OP_EQ, token_bucket_refill(&b, START_TS + SEC*64));
|
||||
tt_int_op(b.read_bucket, OP_GT, -8*KB-200);
|
||||
tt_int_op(b.read_bucket, OP_LT, -8*KB+200);
|
||||
// a second passes
|
||||
tt_int_op(1, OP_EQ, token_bucket_refill(&b, START_TS + SEC*65));
|
||||
tt_int_op(b.read_bucket, OP_GT, 8*KB-200);
|
||||
tt_int_op(b.read_bucket, OP_LT, 8*KB+200);
|
||||
|
||||
// a ridiculous amount of time passes
|
||||
tt_int_op(0, OP_EQ, token_bucket_refill(&b, START_TS + SEC*64));
|
||||
tt_int_op(b.read_bucket, OP_EQ, b.burst);
|
||||
|
||||
done:
|
||||
;
|
||||
}
|
||||
|
||||
#define BWMGT(name) \
|
||||
{ #name, test_bwmgt_ ## name , 0, NULL, NULL }
|
||||
|
||||
struct testcase_t bwmgt_tests[] = {
|
||||
BWMGT(token_buf_init),
|
||||
BWMGT(token_buf_adjust),
|
||||
BWMGT(token_buf_dec),
|
||||
BWMGT(token_buf_refill),
|
||||
END_OF_TESTCASES
|
||||
};
|
||||
|
||||
Loading…
Reference in New Issue