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MINOR: listener: support another thread dispatch mode: "fair"

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This new algorithm for rebalancing incoming connections to multiple
threads is simpler and instead of considering the threads load, it will
only cycle through all of them, offering a fair share of the traffic to
each thread. It may be well suited for short-lived connections but is
also convenient for very large thread counts where it's not always certain
that the least loaded thread will always be found.
This commit is contained in:
Willy Tarreau 2023-04-20 15:40:38 +02:00
parent 6a4d48b736
commit 84fe1f479b
4 changed files with 36 additions and 15 deletions
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23
doc/configuration.txt
View File

@ -3023,16 +3023,23 @@ tune.idletimer <timeout>
clicking). There should be no reason for changing this value. Please check
tune.ssl.maxrecord below.
tune.listener.multi-queue { on | off }
Enables ('on') or disables ('off') the listener's multi-queue accept which
spreads the incoming traffic to all threads a "bind" line is allowed to run
on instead of taking them for itself. This provides a smoother traffic
tune.listener.multi-queue { on | fair | off }
Enables ('on' / 'fair') or disables ('off') the listener's multi-queue accept
which spreads the incoming traffic to all threads a "bind" line is allowed to
run on instead of taking them for itself. This provides a smoother traffic
distribution and scales much better, especially in environments where threads
may be unevenly loaded due to external activity (network interrupts colliding
with one thread for example). This option is enabled by default, but it may
be forcefully disabled for troubleshooting or for situations where it is
estimated that the operating system already provides a good enough
distribution and connections are extremely short-lived.
with one thread for example). The default mode, "on", optimizes the choice of
a thread by picking in a sample the one with the less connections. It is
often the best choice when connections are long-lived as it manages to keep
all threads busy. A second mode, "fair", instead cycles through all threads
regardless of their instant load level. It can be better suited for short-
lived connections, or on machines with very large numbers of threads where
the probability to find the least loaded thread with the first mode is low.
Finally it is possible to forcefully disable the redistribution mechanism
using "off" for troubleshooting, or for situations where connections are
short-lived and it is estimated that the operating system alredy provides a
good enough distribution. The default is "on".
tune.lua.forced-yield <number>
This directive forces the Lua engine to execute a yield each <number> of

5
include/haproxy/global-t.h
View File

@ -66,7 +66,7 @@
#define GTUNE_USE_SYSTEMD (1<<10)
#define GTUNE_BUSY_POLLING (1<<11)
#define GTUNE_LISTENER_MQ (1<<12)
/* unused: (1<<12) */
#define GTUNE_SET_DUMPABLE (1<<13)
#define GTUNE_USE_EVPORTS (1<<14)
#define GTUNE_STRICT_LIMITS (1<<15)
@ -81,6 +81,9 @@
#define GTUNE_QUIC_SOCK_PER_CONN (1<<24)
#define GTUNE_NO_QUIC (1<<25)
#define GTUNE_USE_FAST_FWD (1<<26)
#define GTUNE_LISTENER_MQ_FAIR (1<<27)
#define GTUNE_LISTENER_MQ_OPT (1<<28)
#define GTUNE_LISTENER_MQ_ANY (GTUNE_LISTENER_MQ_FAIR | GTUNE_LISTENER_MQ_OPT)
/* SSL server verify mode */
enum {

2
src/haproxy.c
View File

@ -187,7 +187,7 @@ struct global global = {
}
},
.tune = {
.options = GTUNE_LISTENER_MQ,
.options = GTUNE_LISTENER_MQ_OPT,
.bufsize = (BUFSIZE + 2*sizeof(void *) - 1) & -(2*sizeof(void *)),
.maxrewrite = MAXREWRITE,
.reserved_bufs = RESERVED_BUFS,

21
src/listener.c
View File

@ -1099,7 +1099,7 @@ void listener_accept(struct listener *l)
#if defined(USE_THREAD)
mask = l->rx.bind_thread & _HA_ATOMIC_LOAD(&tg->threads_enabled);
if (atleast2(mask) && (global.tune.options & GTUNE_LISTENER_MQ) && !stopping) {
if (atleast2(mask) && (global.tune.options & GTUNE_LISTENER_MQ_ANY) && !stopping) {
struct accept_queue_ring *ring;
unsigned int t, t0, t1, t2;
int base = tg->base;
@ -1140,6 +1140,14 @@ void listener_accept(struct listener *l)
t1 += my_ffsl(m1) - 1;
}
/* if running in round-robin mode ("fair"), we don't need
* to go further.
*/
if ((global.tune.options & GTUNE_LISTENER_MQ_ANY) == GTUNE_LISTENER_MQ_FAIR) {
t = t1;
goto updt_t1;
}
if (unlikely(!(m2 & (1UL << t2)) || t1 == t2)) {
/* highest bit not set */
if (!m2)
@ -1184,6 +1192,7 @@ void listener_accept(struct listener *l)
}
else {
t = t1;
updt_t1:
t1++;
if (t1 >= LONGBITS)
t1 = 0;
@ -1898,7 +1907,7 @@ static int bind_parse_thread(char **args, int cur_arg, struct proxy *px, struct
return 0;
}
/* config parser for global "tune.listener.multi-queue", accepts "on" or "off" */
/* config parser for global "tune.listener.multi-queue", accepts "on", "fair" or "off" */
static int cfg_parse_tune_listener_mq(char **args, int section_type, struct proxy *curpx,
const struct proxy *defpx, const char *file, int line,
char **err)
@ -1907,11 +1916,13 @@ static int cfg_parse_tune_listener_mq(char **args, int section_type, struct prox
return -1;
if (strcmp(args[1], "on") == 0)
global.tune.options |= GTUNE_LISTENER_MQ;
global.tune.options = (global.tune.options & ~GTUNE_LISTENER_MQ_ANY) | GTUNE_LISTENER_MQ_OPT;
else if (strcmp(args[1], "fair") == 0)
global.tune.options = (global.tune.options & ~GTUNE_LISTENER_MQ_ANY) | GTUNE_LISTENER_MQ_FAIR;
else if (strcmp(args[1], "off") == 0)
global.tune.options &= ~GTUNE_LISTENER_MQ;
global.tune.options &= ~GTUNE_LISTENER_MQ_ANY;
else {
memprintf(err, "'%s' expects either 'on' or 'off' but got '%s'.", args[0], args[1]);
memprintf(err, "'%s' expects either 'on', 'fair', or 'off' but got '%s'.", args[0], args[1]);
return -1;
}
return 0;