sarah
/
tor
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
tor/src/or/scheduler_kist.c

837 lines
30 KiB
C
Raw Permalink Blame History

/* Copyright (c) 2017, The Tor Project, Inc. */
/* See LICENSE for licensing information */
#define SCHEDULER_KIST_PRIVATE
#include "or.h"
#include "buffers.h"
#include "config.h"
#include "connection.h"
#include "networkstatus.h"
#define TOR_CHANNEL_INTERNAL_
#include "channel.h"
#include "channeltls.h"
#define SCHEDULER_PRIVATE_
#include "scheduler.h"
#define TLS_PER_CELL_OVERHEAD 29
#ifdef HAVE_KIST_SUPPORT
/* Kernel interface needed for KIST. */
#include <netinet/tcp.h>
#include <linux/sockios.h>
#endif /* HAVE_KIST_SUPPORT */
/*****************************************************************************
* Data structures and supporting functions
*****************************************************************************/
/* Socket_table hash table stuff. The socket_table keeps track of per-socket
* limit information imposed by kist and used by kist. */
static uint32_t
socket_table_ent_hash(const socket_table_ent_t *ent)
{
return (uint32_t)ent->chan->global_identifier;
}
static unsigned
socket_table_ent_eq(const socket_table_ent_t *a, const socket_table_ent_t *b)
{
return a->chan == b->chan;
}
typedef HT_HEAD(socket_table_s, socket_table_ent_s) socket_table_t;
static socket_table_t socket_table = HT_INITIALIZER();
HT_PROTOTYPE(socket_table_s, socket_table_ent_s, node, socket_table_ent_hash,
socket_table_ent_eq)
HT_GENERATE2(socket_table_s, socket_table_ent_s, node, socket_table_ent_hash,
socket_table_ent_eq, 0.6, tor_reallocarray, tor_free_)
/* outbuf_table hash table stuff. The outbuf_table keeps track of which
* channels have data sitting in their outbuf so the kist scheduler can force
* a write from outbuf to kernel periodically during a run and at the end of a
* run. */
typedef struct outbuf_table_ent_s {
HT_ENTRY(outbuf_table_ent_s) node;
channel_t *chan;
} outbuf_table_ent_t;
static uint32_t
outbuf_table_ent_hash(const outbuf_table_ent_t *ent)
{
return (uint32_t)ent->chan->global_identifier;
}
static unsigned
outbuf_table_ent_eq(const outbuf_table_ent_t *a, const outbuf_table_ent_t *b)
{
return a->chan->global_identifier == b->chan->global_identifier;
}
HT_PROTOTYPE(outbuf_table_s, outbuf_table_ent_s, node, outbuf_table_ent_hash,
outbuf_table_ent_eq)
HT_GENERATE2(outbuf_table_s, outbuf_table_ent_s, node, outbuf_table_ent_hash,
outbuf_table_ent_eq, 0.6, tor_reallocarray, tor_free_)
/*****************************************************************************
* Other internal data
*****************************************************************************/
/* Store the last time the scheduler was run so we can decide when to next run
* the scheduler based on it. */
static monotime_t scheduler_last_run;
/* This is a factor for the extra_space calculation in kist per-socket limits.
* It is the number of extra congestion windows we want to write to the kernel.
*/
static double sock_buf_size_factor = 1.0;
/* How often the scheduler runs. */
STATIC int sched_run_interval = KIST_SCHED_RUN_INTERVAL_DEFAULT;
#ifdef HAVE_KIST_SUPPORT
/* Indicate if KIST lite mode is on or off. We can disable it at runtime.
* Important to have because of the KISTLite -> KIST possible transition. */
static unsigned int kist_lite_mode = 0;
/* Indicate if we don't have the kernel support. This can happen if the kernel
* changed and it doesn't recognized the values passed to the syscalls needed
* by KIST. In that case, fallback to the naive approach. */
static unsigned int kist_no_kernel_support = 0;
#else /* !(defined(HAVE_KIST_SUPPORT)) */
static unsigned int kist_lite_mode = 1;
#endif /* defined(HAVE_KIST_SUPPORT) */
/*****************************************************************************
* Internally called function implementations
*****************************************************************************/
/* Little helper function to get the length of a channel's output buffer */
static inline size_t
channel_outbuf_length(channel_t *chan)
{
/* In theory, this can not happen because we can not scheduler a channel
* without a connection that has its outbuf initialized. Just in case, bug
* on this so we can understand a bit more why it happened. */
if (SCHED_BUG(BASE_CHAN_TO_TLS(chan)->conn == NULL, chan)) {
return 0;
}
return buf_datalen(TO_CONN(BASE_CHAN_TO_TLS(chan)->conn)->outbuf);
}
/* Little helper function for HT_FOREACH_FN. */
static int
each_channel_write_to_kernel(outbuf_table_ent_t *ent, void *data)
{
(void) data; /* Make compiler happy. */
channel_write_to_kernel(ent->chan);
return 0; /* Returning non-zero removes the element from the table. */
}
/* Free the given outbuf table entry ent. */
static int
free_outbuf_info_by_ent(outbuf_table_ent_t *ent, void *data)
{
(void) data; /* Make compiler happy. */
log_debug(LD_SCHED, "Freeing outbuf table entry from chan=%" PRIu64,
ent->chan->global_identifier);
tor_free(ent);
return 1; /* So HT_FOREACH_FN will remove the element */
}
/* Free the given socket table entry ent. */
static int
free_socket_info_by_ent(socket_table_ent_t *ent, void *data)
{
(void) data; /* Make compiler happy. */
log_debug(LD_SCHED, "Freeing socket table entry from chan=%" PRIu64,
ent->chan->global_identifier);
tor_free(ent);
return 1; /* So HT_FOREACH_FN will remove the element */
}
/* Clean up socket_table. Probably because the KIST sched impl is going away */
static void
free_all_socket_info(void)
{
HT_FOREACH_FN(socket_table_s, &socket_table, free_socket_info_by_ent, NULL);
HT_CLEAR(socket_table_s, &socket_table);
}
static socket_table_ent_t *
socket_table_search(socket_table_t *table, const channel_t *chan)
{
socket_table_ent_t search, *ent = NULL;
search.chan = chan;
ent = HT_FIND(socket_table_s, table, &search);
return ent;
}
/* Free a socket entry in table for the given chan. */
static void
free_socket_info_by_chan(socket_table_t *table, const channel_t *chan)
{
socket_table_ent_t *ent = NULL;
ent = socket_table_search(table, chan);
if (!ent)
return;
log_debug(LD_SCHED, "scheduler free socket info for chan=%" PRIu64,
chan->global_identifier);
HT_REMOVE(socket_table_s, table, ent);
free_socket_info_by_ent(ent, NULL);
}
/* Perform system calls for the given socket in order to calculate kist's
* per-socket limit as documented in the function body. */
MOCK_IMPL(void,
update_socket_info_impl, (socket_table_ent_t *ent))
{
#ifdef HAVE_KIST_SUPPORT
int64_t tcp_space, extra_space;
const tor_socket_t sock =
TO_CONN(BASE_CHAN_TO_TLS((channel_t *) ent->chan)->conn)->s;
struct tcp_info tcp;
socklen_t tcp_info_len = sizeof(tcp);
if (kist_no_kernel_support || kist_lite_mode) {
goto fallback;
}
/* Gather information */
if (getsockopt(sock, SOL_TCP, TCP_INFO, (void *)&(tcp), &tcp_info_len) < 0) {
if (errno == EINVAL) {
/* Oops, this option is not provided by the kernel, we'll have to
* disable KIST entirely. This can happen if tor was built on a machine
* with the support previously or if the kernel was updated and lost the
* support. */
log_notice(LD_SCHED, "Looks like our kernel doesn't have the support "
"for KIST anymore. We will fallback to the naive "
"approach. Remove KIST from the Schedulers list "
"to disable.");
kist_no_kernel_support = 1;
}
goto fallback;
}
if (ioctl(sock, SIOCOUTQNSD, &(ent->notsent)) < 0) {
if (errno == EINVAL) {
log_notice(LD_SCHED, "Looks like our kernel doesn't have the support "
"for KIST anymore. We will fallback to the naive "
"approach. Remove KIST from the Schedulers list "
"to disable.");
/* Same reason as the above. */
kist_no_kernel_support = 1;
}
goto fallback;
}
ent->cwnd = tcp.tcpi_snd_cwnd;
ent->unacked = tcp.tcpi_unacked;
ent->mss = tcp.tcpi_snd_mss;
/* In order to reduce outbound kernel queuing delays and thus improve Tor's
* ability to prioritize circuits, KIST wants to set a socket write limit
* that is near the amount that the socket would be able to immediately send
* into the Internet.
*
* We first calculate how much the socket could send immediately (assuming
* completely full packets) according to the congestion window and the number
* of unacked packets.
*
* Then we add a little extra space in a controlled way. We do this so any
* when the kernel gets ACKs back for data currently sitting in the "TCP
* space", it will already have some more data to send immediately. It will
* not have to wait for the scheduler to run again. The amount of extra space
* is a factor of the current congestion window. With the suggested
* sock_buf_size_factor value of 1.0, we allow at most 2*cwnd bytes to sit in
* the kernel: 1 cwnd on the wire waiting for ACKs and 1 cwnd ready and
* waiting to be sent when those ACKs finally come.
*
* In the below diagram, we see some bytes in the TCP-space (denoted by '*')
* that have be sent onto the wire and are waiting for ACKs. We have a little
* more room in "TCP space" that we can fill with data that will be
* immediately sent. We also see the "extra space" KIST calculates. The sum
* of the empty "TCP space" and the "extra space" is the kist-imposed write
* limit for this socket.
*
* <----------------kernel-outbound-socket-queue----------------|
* <*********---------------------------------------------------|
* |----TCP-space-----|----extra-space-----|
* |------------------|
* ^ ((cwnd - unacked) * mss) bytes
* |--------------------|
* ^ ((cwnd * mss) * factor) bytes
*/
/* These values from the kernel are uint32_t, they will always fit into a
* int64_t tcp_space variable but if the congestion window cwnd is smaller
* than the unacked packets, the remaining TCP space is set to 0. */
if (ent->cwnd >= ent->unacked) {
tcp_space = (ent->cwnd - ent->unacked) * (int64_t)(ent->mss);
} else {
tcp_space = 0;
}
/* The clamp_double_to_int64 makes sure the first part fits into an int64_t.
* In fact, if sock_buf_size_factor is still forced to be >= 0 in config.c,
* then it will be positive for sure. Then we subtract a uint32_t. Getting a
* negative value is OK, see after how it is being handled. */
extra_space =
clamp_double_to_int64(
(ent->cwnd * (int64_t)ent->mss) * sock_buf_size_factor) -
ent->notsent;
if ((tcp_space + extra_space) < 0) {
/* This means that the "notsent" queue is just too big so we shouldn't put
* more in the kernel for now. */
ent->limit = 0;
} else {
/* The positive sum of two int64_t will always fit into an uint64_t.
* And we know this will always be positive, since we checked above. */
ent->limit = (uint64_t)tcp_space + (uint64_t)extra_space;
}
return;
#else /* !(defined(HAVE_KIST_SUPPORT)) */
goto fallback;
#endif /* defined(HAVE_KIST_SUPPORT) */
fallback:
/* If all of a sudden we don't have kist support, we just zero out all the
* variables for this socket since we don't know what they should be. We
* also allow the socket to write as much as it can from the estimated
* number of cells the lower layer can accept, effectively returning it to
* Vanilla scheduler behavior. */
ent->cwnd = ent->unacked = ent->mss = ent->notsent = 0;
/* This function calls the specialized channel object (currently channeltls)
* and ask how many cells it can write on the outbuf which we then multiply
* by the size of the cells for this channel. The cast is because this
* function requires a non-const channel object, meh. */
ent->limit = channel_num_cells_writeable((channel_t *) ent->chan) *
(get_cell_network_size(ent->chan->wide_circ_ids) +
TLS_PER_CELL_OVERHEAD);
}
/* Given a socket that isn't in the table, add it.
* Given a socket that is in the table, re-init values that need init-ing
* every scheduling run
*/
static void
init_socket_info(socket_table_t *table, const channel_t *chan)
{
socket_table_ent_t *ent = NULL;
ent = socket_table_search(table, chan);
if (!ent) {
log_debug(LD_SCHED, "scheduler init socket info for chan=%" PRIu64,
chan->global_identifier);
ent = tor_malloc_zero(sizeof(*ent));
ent->chan = chan;
HT_INSERT(socket_table_s, table, ent);
}
ent->written = 0;
}
/* Add chan to the outbuf table if it isn't already in it. If it is, then don't
* do anything */
static void
outbuf_table_add(outbuf_table_t *table, channel_t *chan)
{
outbuf_table_ent_t search, *ent;
search.chan = chan;
ent = HT_FIND(outbuf_table_s, table, &search);
if (!ent) {
log_debug(LD_SCHED, "scheduler init outbuf info for chan=%" PRIu64,
chan->global_identifier);
ent = tor_malloc_zero(sizeof(*ent));
ent->chan = chan;
HT_INSERT(outbuf_table_s, table, ent);
}
}
static void
outbuf_table_remove(outbuf_table_t *table, channel_t *chan)
{
outbuf_table_ent_t search, *ent;
search.chan = chan;
ent = HT_FIND(outbuf_table_s, table, &search);
if (ent) {
HT_REMOVE(outbuf_table_s, table, ent);
free_outbuf_info_by_ent(ent, NULL);
}
}
/* Set the scheduler running interval. */
static void
set_scheduler_run_interval(void)
{
int old_sched_run_interval = sched_run_interval;
sched_run_interval = kist_scheduler_run_interval();
if (old_sched_run_interval != sched_run_interval) {
log_info(LD_SCHED, "Scheduler KIST changing its running interval "
"from %" PRId32 " to %" PRId32,
old_sched_run_interval, sched_run_interval);
}
}
/* Return true iff the channel hasn't hit its kist-imposed write limit yet */
static int
socket_can_write(socket_table_t *table, const channel_t *chan)
{
socket_table_ent_t *ent = NULL;
ent = socket_table_search(table, chan);
if (SCHED_BUG(!ent, chan)) {
return 1; // Just return true, saying that kist wouldn't limit the socket
}
/* We previously calculated a write limit for this socket. In the below
* calculation, first determine how much room is left in bytes. Then divide
* that by the amount of space a cell takes. If there's room for at least 1
* cell, then KIST will allow the socket to write. */
int64_t kist_limit_space =
(int64_t) (ent->limit - ent->written) /
(CELL_MAX_NETWORK_SIZE + TLS_PER_CELL_OVERHEAD);
return kist_limit_space > 0;
}
/* Update the channel's socket kernel information. */
static void
update_socket_info(socket_table_t *table, const channel_t *chan)
{
socket_table_ent_t *ent = NULL;
ent = socket_table_search(table, chan);
if (SCHED_BUG(!ent, chan)) {
return; // Whelp. Entry didn't exist for some reason so nothing to do.
}
update_socket_info_impl(ent);
log_debug(LD_SCHED, "chan=%" PRIu64 " updated socket info, limit: %" PRIu64
", cwnd: %" PRIu32 ", unacked: %" PRIu32
", notsent: %" PRIu32 ", mss: %" PRIu32,
ent->chan->global_identifier, ent->limit, ent->cwnd, ent->unacked,
ent->notsent, ent->mss);
}
/* Increment the channel's socket written value by the number of bytes. */
static void
update_socket_written(socket_table_t *table, channel_t *chan, size_t bytes)
{
socket_table_ent_t *ent = NULL;
ent = socket_table_search(table, chan);
if (SCHED_BUG(!ent, chan)) {
return; // Whelp. Entry didn't exist so nothing to do.
}
log_debug(LD_SCHED, "chan=%" PRIu64 " wrote %lu bytes, old was %" PRIi64,
chan->global_identifier, (unsigned long) bytes, ent->written);
ent->written += bytes;
}
/*
* A naive KIST impl would write every single cell all the way to the kernel.
* That would take a lot of system calls. A less bad KIST impl would write a
* channel's outbuf to the kernel only when we are switching to a different
* channel. But if we have two channels with equal priority, we end up writing
* one cell for each and bouncing back and forth. This KIST impl avoids that
* by only writing a channel's outbuf to the kernel if it has 8 cells or more
* in it.
*/
MOCK_IMPL(int, channel_should_write_to_kernel,
(outbuf_table_t *table, channel_t *chan))
{
outbuf_table_add(table, chan);
/* CELL_MAX_NETWORK_SIZE * 8 because we only want to write the outbuf to the
* kernel if there's 8 or more cells waiting */
return channel_outbuf_length(chan) > (CELL_MAX_NETWORK_SIZE * 8);
}
/* Little helper function to write a channel's outbuf all the way to the
* kernel */
MOCK_IMPL(void, channel_write_to_kernel, (channel_t *chan))
{
log_debug(LD_SCHED, "Writing %lu bytes to kernel for chan %" PRIu64,
(unsigned long)channel_outbuf_length(chan),
chan->global_identifier);
connection_handle_write(TO_CONN(BASE_CHAN_TO_TLS(chan)->conn), 0);
}
/* Return true iff the scheduler has work to perform. */
static int
have_work(void)
{
smartlist_t *cp = get_channels_pending();
IF_BUG_ONCE(!cp) {
return 0; // channels_pending doesn't exist so... no work?
}
return smartlist_len(cp) > 0;
}
/* Function of the scheduler interface: free_all() */
static void
kist_free_all(void)
{
free_all_socket_info();
}
/* Function of the scheduler interface: on_channel_free() */
static void
kist_on_channel_free_fn(const channel_t *chan)
{
free_socket_info_by_chan(&socket_table, chan);
}
/* Function of the scheduler interface: on_new_consensus() */
static void
kist_scheduler_on_new_consensus(void)
{
set_scheduler_run_interval();
}
/* Function of the scheduler interface: on_new_options() */
static void
kist_scheduler_on_new_options(void)
{
sock_buf_size_factor = get_options()->KISTSockBufSizeFactor;
/* Calls kist_scheduler_run_interval which calls get_options(). */
set_scheduler_run_interval();
}
/* Function of the scheduler interface: init() */
static void
kist_scheduler_init(void)
{
/* When initializing the scheduler, the last run could be 0 because it is
* declared static or a value in the past that was set when it was last
* used. In both cases, we want to initialize it to now so we don't risk
* using the value 0 which doesn't play well with our monotonic time
* interface.
*
* One side effect is that the first scheduler run will be at the next tick
* that is in now + 10 msec (KIST_SCHED_RUN_INTERVAL_DEFAULT) by default. */
monotime_get(&scheduler_last_run);
kist_scheduler_on_new_options();
IF_BUG_ONCE(sched_run_interval == 0) {
log_warn(LD_SCHED, "We are initing the KIST scheduler and noticed the "
"KISTSchedRunInterval is telling us to not use KIST. That's "
"weird! We'll continue using KIST, but at %" PRId32 "ms.",
KIST_SCHED_RUN_INTERVAL_DEFAULT);
sched_run_interval = KIST_SCHED_RUN_INTERVAL_DEFAULT;
}
}
/* Function of the scheduler interface: schedule() */
static void
kist_scheduler_schedule(void)
{
struct monotime_t now;
struct timeval next_run;
int64_t diff;
if (!have_work()) {
return;
}
monotime_get(&now);
/* If time is really monotonic, we can never have now being smaller than the
* last scheduler run. The scheduler_last_run at first is set to 0.
* Unfortunately, not all platforms guarantee monotonic time so we log at
* info level but don't make it more noisy. */
diff = monotime_diff_msec(&scheduler_last_run, &now);
if (diff < 0) {
log_info(LD_SCHED, "Monotonic time between now and last run of scheduler "
"is negative: %" PRId64 ". Setting diff to 0.", diff);
diff = 0;
}
if (diff < sched_run_interval) {
next_run.tv_sec = 0;
/* Takes 1000 ms -> us. This will always be valid because diff can NOT be
* negative and can NOT be bigger than sched_run_interval so values can
* only go from 1000 usec (diff set to interval - 1) to 100000 usec (diff
* set to 0) for the maximum allowed run interval (100ms). */
next_run.tv_usec = (int) ((sched_run_interval - diff) * 1000);
/* Re-adding an event reschedules it. It does not duplicate it. */
scheduler_ev_add(&next_run);
} else {
scheduler_ev_active();
}
}
/* Function of the scheduler interface: run() */
static void
kist_scheduler_run(void)
{
/* Define variables */
channel_t *chan = NULL; // current working channel
/* The last distinct chan served in a sched loop. */
channel_t *prev_chan = NULL;
int flush_result; // temporarily store results from flush calls
/* Channels to be re-adding to pending at the end */
smartlist_t *to_readd = NULL;
smartlist_t *cp = get_channels_pending();
outbuf_table_t outbuf_table = HT_INITIALIZER();
/* For each pending channel, collect new kernel information */
SMARTLIST_FOREACH_BEGIN(cp, const channel_t *, pchan) {
init_socket_info(&socket_table, pchan);
update_socket_info(&socket_table, pchan);
} SMARTLIST_FOREACH_END(pchan);
log_debug(LD_SCHED, "Running the scheduler. %d channels pending",
smartlist_len(cp));
/* The main scheduling loop. Loop until there are no more pending channels */
while (smartlist_len(cp) > 0) {
/* get best channel */
chan = smartlist_pqueue_pop(cp, scheduler_compare_channels,
offsetof(channel_t, sched_heap_idx));
if (SCHED_BUG(!chan, NULL)) {
/* Some-freaking-how a NULL got into the channels_pending. That should
* never happen, but it should be harmless to ignore it and keep looping.
*/
continue;
}
outbuf_table_add(&outbuf_table, chan);
/* if we have switched to a new channel, consider writing the previous
* channel's outbuf to the kernel. */
if (!prev_chan) {
prev_chan = chan;
}
if (prev_chan != chan) {
if (channel_should_write_to_kernel(&outbuf_table, prev_chan)) {
channel_write_to_kernel(prev_chan);
outbuf_table_remove(&outbuf_table, prev_chan);
}
prev_chan = chan;
}
/* Only flush and write if the per-socket limit hasn't been hit */
if (socket_can_write(&socket_table, chan)) {
/* flush to channel queue/outbuf */
flush_result = (int)channel_flush_some_cells(chan, 1); // 1 for num cells
/* XXX: While flushing cells, it is possible that the connection write
* fails leading to the channel to be closed which triggers a release
* and free its entry in the socket table. And because of a engineering
* design issue, the error is not propagated back so we don't get an
* error at this point. So before we continue, make sure the channel is
* open and if not just ignore it. See #23751. */
if (!CHANNEL_IS_OPEN(chan)) {
/* Channel isn't open so we put it back in IDLE mode. It is either
* renegotiating its TLS session or about to be released. */
scheduler_set_channel_state(chan, SCHED_CHAN_IDLE);
continue;
}
/* flush_result has the # cells flushed */
if (flush_result > 0) {
update_socket_written(&socket_table, chan, flush_result *
(CELL_MAX_NETWORK_SIZE + TLS_PER_CELL_OVERHEAD));
} else {
/* XXX: This can happen because tor sometimes does flush in an
* opportunistic way cells from the circuit to the outbuf so the
* channel can end up here without having anything to flush nor needed
* to write to the kernel. Hopefully we'll fix that soon but for now
* we have to handle this case which happens kind of often. */
log_debug(LD_SCHED,
"We didn't flush anything on a chan that we think "
"can write and wants to write. The channel's state is '%s' "
"and in scheduler state '%s'. We're going to mark it as "
"waiting_for_cells (as that's most likely the issue) and "
"stop scheduling it this round.",
channel_state_to_string(chan->state),
get_scheduler_state_string(chan->scheduler_state));
scheduler_set_channel_state(chan, SCHED_CHAN_WAITING_FOR_CELLS);
continue;
}
}
/* Decide what to do with the channel now */
if (!channel_more_to_flush(chan) &&
!socket_can_write(&socket_table, chan)) {
/* Case 1: no more cells to send, and cannot write */
/*
* You might think we should put the channel in SCHED_CHAN_IDLE. And
* you're probably correct. While implementing KIST, we found that the
* scheduling system would sometimes lose track of channels when we did
* that. We suspect it has to do with the difference between "can't
* write because socket/outbuf is full" and KIST's "can't write because
* we've arbitrarily decided that that's enough for now." Sometimes
* channels run out of cells at the same time they hit their
* kist-imposed write limit and maybe the rest of Tor doesn't put the
* channel back in pending when it is supposed to.
*
* This should be investigated again. It is as simple as changing
* SCHED_CHAN_WAITING_FOR_CELLS to SCHED_CHAN_IDLE and seeing if Tor
* starts having serious throughput issues. Best done in shadow/chutney.
*/
scheduler_set_channel_state(chan, SCHED_CHAN_WAITING_FOR_CELLS);
} else if (!channel_more_to_flush(chan)) {
/* Case 2: no more cells to send, but still open for writes */
scheduler_set_channel_state(chan, SCHED_CHAN_WAITING_FOR_CELLS);
} else if (!socket_can_write(&socket_table, chan)) {
/* Case 3: cells to send, but cannot write */
/*
* We want to write, but can't. If we left the channel in
* channels_pending, we would never exit the scheduling loop. We need to
* add it to a temporary list of channels to be added to channels_pending
* after the scheduling loop is over. They can hopefully be taken care of
* in the next scheduling round.
*/
if (!to_readd) {
to_readd = smartlist_new();
}
smartlist_add(to_readd, chan);
} else {
/* Case 4: cells to send, and still open for writes */
scheduler_set_channel_state(chan, SCHED_CHAN_PENDING);
if (!SCHED_BUG(chan->sched_heap_idx != -1, chan)) {
smartlist_pqueue_add(cp, scheduler_compare_channels,
offsetof(channel_t, sched_heap_idx), chan);
}
}
} /* End of main scheduling loop */
/* Write the outbuf of any channels that still have data */
HT_FOREACH_FN(outbuf_table_s, &outbuf_table, each_channel_write_to_kernel,
NULL);
/* We are done with it. */
HT_FOREACH_FN(outbuf_table_s, &outbuf_table, free_outbuf_info_by_ent, NULL);
HT_CLEAR(outbuf_table_s, &outbuf_table);
log_debug(LD_SCHED, "len pending=%d, len to_readd=%d",
smartlist_len(cp),
(to_readd ? smartlist_len(to_readd) : -1));
/* Re-add any channels we need to */
if (to_readd) {
SMARTLIST_FOREACH_BEGIN(to_readd, channel_t *, readd_chan) {
scheduler_set_channel_state(readd_chan, SCHED_CHAN_PENDING);
if (!smartlist_contains(cp, readd_chan)) {
if (!SCHED_BUG(chan->sched_heap_idx != -1, chan)) {
/* XXXX Note that the check above is in theory redundant with
* the smartlist_contains check. But let's make sure we're
* not messing anything up, and leave them both for now. */
smartlist_pqueue_add(cp, scheduler_compare_channels,
offsetof(channel_t, sched_heap_idx), readd_chan);
}
}
} SMARTLIST_FOREACH_END(readd_chan);
smartlist_free(to_readd);
}
monotime_get(&scheduler_last_run);
}
/*****************************************************************************
* Externally called function implementations not called through scheduler_t
*****************************************************************************/
/* Stores the kist scheduler function pointers. */
static scheduler_t kist_scheduler = {
.type = SCHEDULER_KIST,
.free_all = kist_free_all,
.on_channel_free = kist_on_channel_free_fn,
.init = kist_scheduler_init,
.on_new_consensus = kist_scheduler_on_new_consensus,
.schedule = kist_scheduler_schedule,
.run = kist_scheduler_run,
.on_new_options = kist_scheduler_on_new_options,
};
/* Return the KIST scheduler object. If it didn't exists, return a newly
* allocated one but init() is not called. */
scheduler_t *
get_kist_scheduler(void)
{
return &kist_scheduler;
}
/* Check the torrc (and maybe consensus) for the configured KIST scheduler run
* interval.
* - If torrc > 0, then return the positive torrc value (should use KIST, and
* should use the set value)
* - If torrc == 0, then look in the consensus for what the value should be.
* - If == 0, then return 0 (don't use KIST)
* - If > 0, then return the positive consensus value
* - If consensus doesn't say anything, return 10 milliseconds, default.
*/
int
kist_scheduler_run_interval(void)
{
int run_interval = get_options()->KISTSchedRunInterval;
if (run_interval != 0) {
log_debug(LD_SCHED, "Found KISTSchedRunInterval=%" PRId32 " in torrc. "
"Using that.", run_interval);
return run_interval;
}
log_debug(LD_SCHED, "KISTSchedRunInterval=0, turning to the consensus.");
/* Will either be the consensus value or the default. Note that 0 can be
* returned which means the consensus wants us to NOT use KIST. */
return networkstatus_get_param(NULL, "KISTSchedRunInterval",
KIST_SCHED_RUN_INTERVAL_DEFAULT,
KIST_SCHED_RUN_INTERVAL_MIN,
KIST_SCHED_RUN_INTERVAL_MAX);
}
/* Set KISTLite mode that is KIST without kernel support. */
void
scheduler_kist_set_lite_mode(void)
{
kist_lite_mode = 1;
kist_scheduler.type = SCHEDULER_KIST_LITE;
log_info(LD_SCHED,
"Setting KIST scheduler without kernel support (KISTLite mode)");
}
/* Set KIST mode that is KIST with kernel support. */
void
scheduler_kist_set_full_mode(void)
{
kist_lite_mode = 0;
kist_scheduler.type = SCHEDULER_KIST;
log_info(LD_SCHED,
"Setting KIST scheduler with kernel support (KIST mode)");
}
#ifdef HAVE_KIST_SUPPORT
/* Return true iff the scheduler subsystem should use KIST. */
int
scheduler_can_use_kist(void)
{
if (kist_no_kernel_support) {
/* We have no kernel support so we can't use KIST. */
return 0;
}
/* We do have the support, time to check if we can get the interval that the
* consensus can be disabling. */
int run_interval = kist_scheduler_run_interval();
log_debug(LD_SCHED, "Determined KIST sched_run_interval should be "
"%" PRId32 ". Can%s use KIST.",
run_interval, (run_interval > 0 ? "" : " not"));
return run_interval > 0;
}
#else /* !(defined(HAVE_KIST_SUPPORT)) */
int
scheduler_can_use_kist(void)
{
return 0;
}
#endif /* defined(HAVE_KIST_SUPPORT) */
Reference in New Issue View Git Blame Copy Permalink