File 2224-erts-Add-option-IOs-to-disable-scheduler-p... of Package erlang

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File 2224-erts-Add-option-IOs-to-disable-scheduler-polling.patch of Package erlang (Revision e0e016f64b94e78db3440770f914218d)

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From de2667593b7560ba809fbc90a1905508a93c18ef Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Fri, 4 Mar 2022 22:50:41 +0100
Subject: [PATCH 4/4] erts: Add option +IOs to disable scheduler polling

Enabled (true) by default.
---
 erts/doc/src/erl_cmd.xml                | 12 +++
 erts/emulator/beam/erl_port_task.c      | 30 ++++----
 erts/emulator/beam/erl_process.c        | 32 ++++----
 erts/emulator/sys/common/erl_check_io.c | 99 +++++++++++++++----------
 erts/emulator/sys/common/erl_check_io.h | 18 +++++
 erts/emulator/test/scheduler_SUITE.erl  | 51 +++++++++++++
 erts/etc/common/erlexec.c               | 10 +++
 7 files changed, 182 insertions(+), 70 deletions(-)

diff --git a/erts/doc/src/erl_cmd.xml b/erts/doc/src/erl_cmd.xml
index 6eeaf27eaf..98412fcf25 100644
--- a/erts/doc/src/erl_cmd.xml
+++ b/erts/doc/src/erl_cmd.xml
@@ -969,6 +969,18 @@ $ <input>erl \
 <c>+IOt</c> are used, <c>+IOPt</c> is ignored.
 
 </item>
+ <tag><marker id="+IOs"/><c>+IOs true|false</c></tag>
+ <item>
+ Enable or disable scheduler thread poll optimization. Default is
+ <c>true</c>.
+ 
+ If enabled, file descriptors that are frequently read may be moved to
+ a special pollset used by scheduler threads. The objective is to
+ reduce the number of system calls and thereby CPU load, but it can
+ in some cases increase scheduling latency for individual file
+ descriptor input events.
+ 
+ </item>
 <tag><marker id="+JPperf"/><c>+JPperf true|false</c></tag>
 <item>
 Enables or disables support for the `perf` profiler when running
diff --git a/erts/emulator/beam/erl_port_task.c b/erts/emulator/beam/erl_port_task.c
index 27ecee8d09..33b6cf1c43 100644
--- a/erts/emulator/beam/erl_port_task.c
+++ b/erts/emulator/beam/erl_port_task.c
@@ -1326,22 +1326,22 @@ erts_port_task_abort(ErtsPortTaskHandle *pthp)
 	 res = - 1; /* Task already aborted, executing, or executed */
 	else {
 	 reset_port_task_handle(pthp);
-
 #if ERTS_POLL_USE_SCHEDULER_POLLING
- switch (ptp->type) {
-	 case ERTS_PORT_TASK_INPUT:
-	 case ERTS_PORT_TASK_OUTPUT:
- if (ptp->u.alive.td.io.is_scheduler_event) {
- ASSERT(erts_atomic_read_nob(
- &erts_port_task_outstanding_io_tasks) > 0);
- erts_atomic_dec_relb(&erts_port_task_outstanding_io_tasks);
+ if (erts_sched_poll_enabled()) {
+ switch (ptp->type) {
+ case ERTS_PORT_TASK_INPUT:
+ case ERTS_PORT_TASK_OUTPUT:
+ if (ptp->u.alive.td.io.is_scheduler_event) {
+ ASSERT(erts_atomic_read_nob(
+ &erts_port_task_outstanding_io_tasks) > 0);
+ erts_atomic_dec_relb(&erts_port_task_outstanding_io_tasks);
+ }
+ break;
+ default:
+ break;
 }
-		break;
-	 default:
-		break;
-	 }
+ }
 #endif
-
 	 res = 0;
 	}
 }
@@ -1844,16 +1844,14 @@ erts_port_task_execute(ErtsRunQueue *runq, Port **curr_port_pp)
 }
 
 ERTS_MSACC_POP_STATE_M();
-
 #if ERTS_POLL_USE_SCHEDULER_POLLING
- if (io_tasks_executed) {
+ if (erts_sched_poll_enabled() && io_tasks_executed) {
 ASSERT(erts_atomic_read_nob(&erts_port_task_outstanding_io_tasks)
 	 >= io_tasks_executed);
 erts_atomic_add_relb(&erts_port_task_outstanding_io_tasks,
 				 -1*io_tasks_executed);
 }
 #endif
-
 ASSERT(runq == erts_get_runq_port(pp));
 
 active = finalize_exec(pp, &execq, processing_busy_q);
diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index c75f67c0d7..fac9ab704b 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -3194,11 +3194,11 @@ aux_thread(void *vix)
 
 #if ERTS_POLL_USE_FALLBACK
 if (ix == 0) {
-#if ERTS_POLL_USE_SCHEDULER_POLLING
-	ssi->psi = erts_create_pollset_thread(-2, tpd);
-#else
-	ssi->psi = erts_create_pollset_thread(-1, tpd);
-#endif
+ if (erts_sched_poll_enabled()) {
+ ssi->psi = erts_create_pollset_thread(-2, tpd);
+ } else {
+ ssi->psi = erts_create_pollset_thread(-1, tpd);
+ }
 }
 #endif
 
@@ -3365,11 +3365,13 @@ try_set_sys_scheduling(void)
 static ERTS_INLINE int
 prepare_for_sys_schedule(void)
 {
- while (!erts_port_task_have_outstanding_io_tasks()
- && try_set_sys_scheduling()) {
- if (!erts_port_task_have_outstanding_io_tasks())
- return 1;
- clear_sys_scheduling();
+ if (erts_sched_poll_enabled()) {
+ while (!erts_port_task_have_outstanding_io_tasks()
+ && try_set_sys_scheduling()) {
+ if (!erts_port_task_have_outstanding_io_tasks())
+ return 1;
+ clear_sys_scheduling();
+ }
 }
 return 0;
 }
@@ -8620,9 +8622,9 @@ sched_thread_func(void *vesdp)
 
 erts_thr_progress_register_managed_thread(esdp, &callbacks, 0, 0);
 
-#if ERTS_POLL_USE_SCHEDULER_POLLING
- esdp->ssi->psi = erts_create_pollset_thread(-1, NULL);
-#endif
+ if (erts_sched_poll_enabled()) {
+ esdp->ssi->psi = erts_create_pollset_thread(-1, NULL);
+ }
 
 #ifdef ERTS_ENABLE_LOCK_CHECK
 {
@@ -9522,7 +9524,9 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls)
 	esdp->virtual_reds = 0;
 
 #if ERTS_POLL_USE_SCHEDULER_POLLING
- fcalls = (int) erts_atomic32_add_read_acqb(&function_calls, reds);
+ if (erts_sched_poll_enabled()) {
+ fcalls = (int)erts_atomic32_add_read_acqb(&function_calls, reds);
+ }
 #endif
 
 	ASSERT(esdp && esdp == erts_get_scheduler_data());
diff --git a/erts/emulator/sys/common/erl_check_io.c b/erts/emulator/sys/common/erl_check_io.c
index 28716b313e..1b12ed3293 100644
--- a/erts/emulator/sys/common/erl_check_io.c
+++ b/erts/emulator/sys/common/erl_check_io.c
@@ -146,7 +146,7 @@ static ErtsPollThread *psiv;
 static ErtsPollSet *flbk_pollset;
 #endif
 #if ERTS_POLL_USE_SCHEDULER_POLLING
-static ErtsPollSet *sched_pollset;
+ErtsPollSet *sched_pollset;
 #endif
 
 typedef struct {
@@ -418,7 +418,7 @@ static ERTS_INLINE ErtsPollSet *
 get_scheduler_pollset(ErtsSysFdType fd)
 {
 #if ERTS_POLL_USE_SCHEDULER_POLLING
- return sched_pollset;
+ return sched_pollset ? sched_pollset : get_pollset(fd);
 #else
 return get_pollset(fd);
 #endif
@@ -506,7 +506,7 @@ erts_io_notify_port_task_executed(ErtsPortTaskType type,
 && (state->events & ERTS_POLL_EV_IN)) {
 
 active_events |= ERTS_POLL_EV_IN;
- if (state->count > 10 && ERTS_POLL_USE_SCHEDULER_POLLING) {
+ if (state->count > 10 && erts_sched_poll_enabled()) {
 if (!(state->flags & ERTS_EV_FLAG_SCHEDULER))
 op = ERTS_POLL_OP_ADD;
 state->flags |= ERTS_EV_FLAG_IN_SCHEDULER|ERTS_EV_FLAG_SCHEDULER;
@@ -514,7 +514,7 @@ erts_io_notify_port_task_executed(ErtsPortTaskType type,
 DEBUG_PRINT_FD("moving to scheduler ps", state);
 } else
 new_events = active_events;
- if (!(state->flags & ERTS_EV_FLAG_FALLBACK) && ERTS_POLL_USE_SCHEDULER_POLLING)
+ if (!(state->flags & ERTS_EV_FLAG_FALLBACK) && erts_sched_poll_enabled())
 state->count++;
 }
 break;
@@ -1800,7 +1800,7 @@ erts_check_io(ErtsPollThread *psi, ErtsMonotonicTime timeout_time, int poll_only
 select/deselect in rapid succession. */
 revents &= state->active_events | ERTS_POLL_EV_NVAL;
 
- if (psi->ps != get_scheduler_pollset(fd) || !ERTS_POLL_USE_SCHEDULER_POLLING) {
+ if (psi->ps != get_scheduler_pollset(fd) || !erts_sched_poll_enabled()) {
 ErtsPollEvents reactive_events;
 state->active_events &= ~revents;
 
@@ -2118,7 +2118,7 @@ get_arg(char* rest, char** argv, int* ip)
 }
 
 static void
-parse_args(int *argc, char **argv, int concurrent_waiters)
+parse_args(int *argc, char **argv, int concurrent_waiters, int* use_sched_poll)
 {
 int i = 0, j;
 int no_pollsets = 0, no_poll_threads = 0,
@@ -2160,8 +2160,16 @@ parse_args(int *argc, char **argv, int concurrent_waiters)
 erts_fprintf(stderr,"bad I/O pollset percentage number: %s\n", arg);
 erts_usage();
 }
- } else {
- break;
+ } else if (sys_strcmp(argv[i]+2, "Os") == 0) {
+ const char *arg = get_arg(argv[i]+4, argv, &i);
+ if (sys_strcmp(arg, "true") == 0) {
+ *use_sched_poll = 1;
+ } else if (sys_strcmp(arg, "false") == 0) {
+ *use_sched_poll = 0;
+ } else {
+ erts_fprintf(stderr,"bad +IOs boolean argument: %s\n", arg);
+ erts_usage();
+ }
 }
 break;
 }
@@ -2229,6 +2237,8 @@ void
 erts_init_check_io(int *argc, char **argv)
 {
 int j, concurrent_waiters, no_poll_threads;
+ int use_sched_poll = ERTS_POLL_USE_SCHEDULER_POLLING;
+
 ERTS_CT_ASSERT((INT_MIN & (ERL_NIF_SELECT_STOP_CALLED |
 ERL_NIF_SELECT_STOP_SCHEDULED |
 ERL_NIF_SELECT_INVALID_EVENT |
@@ -2240,7 +2250,7 @@ erts_init_check_io(int *argc, char **argv)
 erts_poll_init_flbk(NULL);
 #endif
 
- parse_args(argc, argv, concurrent_waiters);
+ parse_args(argc, argv, concurrent_waiters, &use_sched_poll);
 
 /* Create the actual pollsets */
 pollsetv = erts_alloc(ERTS_ALC_T_POLLSET,sizeof(ErtsPollSet *) * erts_no_pollsets);
@@ -2252,10 +2262,16 @@ erts_init_check_io(int *argc, char **argv)
 
 j = -1;
 
+ if (use_sched_poll) {
 #if ERTS_POLL_USE_SCHEDULER_POLLING
- sched_pollset = erts_poll_create_pollset(j--);
- no_poll_threads++;
+ sched_pollset = erts_poll_create_pollset(j--);
+ ASSERT(erts_sched_poll_enabled());
+ no_poll_threads++;
+#else
+ erts_fprintf(stderr,"+IOs true: not supported by this emulator\n");
+ erts_usage();
 #endif
+ }
 
 #if ERTS_POLL_USE_FALLBACK
 flbk_pollset = erts_poll_create_pollset_flbk(j--);
@@ -2272,13 +2288,13 @@ erts_init_check_io(int *argc, char **argv)
 psiv++;
 #endif
 
-#if ERTS_POLL_USE_SCHEDULER_POLLING
- psiv[0].pollres_len = ERTS_CHECK_IO_POLL_RES_LEN;
- psiv[0].pollres = erts_alloc(ERTS_ALC_T_POLLSET,
- sizeof(ErtsPollResFd) * ERTS_CHECK_IO_POLL_RES_LEN);
- psiv[0].ps = get_scheduler_pollset(0);
- psiv++;
-#endif
+ if (erts_sched_poll_enabled()) {
+ psiv[0].pollres_len = ERTS_CHECK_IO_POLL_RES_LEN;
+ psiv[0].pollres = erts_alloc(ERTS_ALC_T_POLLSET,
+ sizeof(ErtsPollResFd) * ERTS_CHECK_IO_POLL_RES_LEN);
+ psiv[0].ps = get_scheduler_pollset(0);
+ psiv++;
+ }
 
 for (j = 0; j < erts_no_poll_threads; j++) {
 psiv[j].pollres_len = ERTS_CHECK_IO_POLL_RES_LEN;
@@ -2336,12 +2352,12 @@ erts_check_io_size(void)
 erts_poll_info(get_fallback_pollset(), &pi);
 res += pi.memory_size;
 #endif
-
 #if ERTS_POLL_USE_SCHEDULER_POLLING
- erts_poll_info(get_scheduler_pollset(0), &pi);
- res += pi.memory_size;
+ if (erts_sched_poll_enabled()) {
+ erts_poll_info(sched_pollset, &pi);
+ res += pi.memory_size;
+ }
 #endif
-
 for (i = 0; i < erts_no_pollsets; i++) {
 erts_poll_info(pollsetv[i], &pi);
 res += pi.memory_size;
@@ -2370,9 +2386,9 @@ erts_check_io_info(void *proc)
 Uint sz, *szp, *hp, **hpp;
 ErtsPollInfo *piv;
 Sint i, j = 0, len;
- int no_pollsets = erts_no_pollsets + ERTS_POLL_USE_FALLBACK + ERTS_POLL_USE_SCHEDULER_POLLING;
+ int no_pollsets = erts_no_pollsets + ERTS_POLL_USE_FALLBACK + erts_sched_poll_enabled();
 ERTS_CT_ASSERT(ERTS_POLL_USE_FALLBACK == 0 || ERTS_POLL_USE_FALLBACK == 1);
- ERTS_CT_ASSERT(ERTS_POLL_USE_SCHEDULER_POLLING == 0 || ERTS_POLL_USE_SCHEDULER_POLLING == 1);
+ ERTS_ASSERT(erts_sched_poll_enabled() == 0 || erts_sched_poll_enabled() == 1);
 
 piv = erts_alloc(ERTS_ALC_T_TMP, sizeof(ErtsPollInfo) * no_pollsets);
 
@@ -2382,14 +2398,14 @@ erts_check_io_info(void *proc)
 piv[0].active_fds = 0;
 piv++;
 #endif
-
 #if ERTS_POLL_USE_SCHEDULER_POLLING
- erts_poll_info(get_scheduler_pollset(0), &piv[0]);
- piv[0].poll_threads = 0;
- piv[0].active_fds = 0;
- piv++;
+ if (erts_sched_poll_enabled()) {
+ erts_poll_info(sched_pollset, &piv[0]);
+ piv[0].poll_threads = 0;
+ piv[0].active_fds = 0;
+ piv++;
+ }
 #endif
-
 for (j = 0; j < erts_no_pollsets; j++) {
 erts_poll_info(pollsetv[j], &piv[j]);
 piv[j].active_fds = 0;
@@ -2438,7 +2454,7 @@ erts_check_io_info(void *proc)
 sz = 0;
 
 piv -= ERTS_POLL_USE_FALLBACK;
- piv -= ERTS_POLL_USE_SCHEDULER_POLLING;
+ piv -= erts_sched_poll_enabled();
 
 bld_it:
 
@@ -2919,18 +2935,19 @@ erts_check_io_debug(ErtsCheckIoDebugInfo *ciodip)
 }
 #endif
 #if ERTS_POLL_USE_SCHEDULER_POLLING
- erts_dsprintf(dsbufp, "--- fds in scheduler pollset ----------------------------\n");
- erts_poll_get_selected_events(get_scheduler_pollset(0), counters.epep,
- drv_ev_state.max_fds);
- for (fd = 0; fd < len; fd++) {
- if (drv_ev_state.v[fd].flags & ERTS_EV_FLAG_SCHEDULER) {
- if (drv_ev_state.v[fd].events && drv_ev_state.v[fd].events != ERTS_POLL_EV_NONE)
- counters.epep[fd] &= ~ERTS_POLL_EV_OUT;
- doit_erts_check_io_debug(&drv_ev_state.v[fd], &counters, dsbufp);
+ if (erts_sched_poll_enabled()) {
+ erts_dsprintf(dsbufp, "--- fds in scheduler pollset ----------------------------\n");
+ erts_poll_get_selected_events(sched_pollset, counters.epep,
+ drv_ev_state.max_fds);
+ for (fd = 0; fd < len; fd++) {
+ if (drv_ev_state.v[fd].flags & ERTS_EV_FLAG_SCHEDULER) {
+ if (drv_ev_state.v[fd].events && drv_ev_state.v[fd].events != ERTS_POLL_EV_NONE)
+ counters.epep[fd] &= ~ERTS_POLL_EV_OUT;
+ doit_erts_check_io_debug(&drv_ev_state.v[fd], &counters, dsbufp);
+ }
 }
 }
 #endif
-
 erts_dsprintf(dsbufp, "--- fds in pollset --------------------------------------\n");
 
 for (i = 0; i < erts_no_pollsets; i++) {
@@ -2942,6 +2959,7 @@ erts_check_io_debug(ErtsCheckIoDebugInfo *ciodip)
 && get_pollset_id(fd) == i) {
 if (counters.epep[fd] != ERTS_POLL_EV_NONE &&
 drv_ev_state.v[fd].flags & ERTS_EV_FLAG_IN_SCHEDULER) {
+ ERTS_ASSERT(erts_sched_poll_enabled());
 /* We add the in flag if it is enabled in the scheduler pollset
 and get_selected_events works on the platform */
 counters.epep[fd] |= ERTS_POLL_EV_IN;
@@ -2950,6 +2968,7 @@ erts_check_io_debug(ErtsCheckIoDebugInfo *ciodip)
 }
 }
 }
+
 for (fd = len ; fd < drv_ev_state.max_fds; fd++) {
 null_des.fd = fd;
 doit_erts_check_io_debug(&null_des, &counters, dsbufp);
diff --git a/erts/emulator/sys/common/erl_check_io.h b/erts/emulator/sys/common/erl_check_io.h
index b96f4f9609..7af984fea9 100644
--- a/erts/emulator/sys/common/erl_check_io.h
+++ b/erts/emulator/sys/common/erl_check_io.h
@@ -112,6 +112,22 @@ typedef struct {
 } ErtsIoTask;
 
 
+ERTS_GLB_INLINE int erts_sched_poll_enabled(void);
+
+#if ERTS_GLB_INLINE_INCL_FUNC_DEF
+
+ERTS_GLB_INLINE int erts_sched_poll_enabled(void)
+{
+#if ERTS_POLL_USE_SCHEDULER_POLLING
+ extern ErtsPollSet *sched_pollset;
+ return (sched_pollset != NULL);
+#else
+ return 0;
+#endif
+}
+
+#endif /* ERTS_GLB_INLINE_INCL_FUNC_DEF */
+
 #endif /* ERL_CHECK_IO_H__ */
 
 #if !defined(ERL_CHECK_IO_C__) && !defined(ERTS_ALLOC_C__)
@@ -133,6 +149,7 @@ extern int erts_no_poll_threads;
 #include "erl_poll.h"
 #include "erl_port_task.h"
 
+
 typedef struct {
 Eterm inport;
 Eterm outport;
@@ -152,3 +169,4 @@ typedef struct {
 } ErtsNifSelectDataState;
 
 #endif /* #ifndef ERL_CHECK_IO_INTERNAL__ */
+
diff --git a/erts/emulator/test/scheduler_SUITE.erl b/erts/emulator/test/scheduler_SUITE.erl
index 817062c397..44000667a0 100644
--- a/erts/emulator/test/scheduler_SUITE.erl
+++ b/erts/emulator/test/scheduler_SUITE.erl
@@ -58,6 +58,7 @@
 	 scheduler_suspend_basic/1,
 	 scheduler_suspend/1,
 	 dirty_scheduler_threads/1,
+ sched_poll/1,
 poll_threads/1,
 	 reader_groups/1,
 otp_16446/1,
@@ -77,6 +78,7 @@ all() ->
 {group, scheduler_bind}, scheduler_threads,
 scheduler_suspend_basic, scheduler_suspend,
 dirty_scheduler_threads,
+ sched_poll,
 poll_threads,
 reader_groups,
 otp_16446,
@@ -1528,6 +1530,54 @@ sst5_loop(N) ->
 erlang:system_flag(multi_scheduling, unblock_normal),
 sst5_loop(N-1).
 
+%% Test scheduler polling: +IOs true|false
+sched_poll(Config) when is_list(Config) ->
+
+ Env = case os:getenv("ERL_AFLAGS") of
+ false ->
+ [];
+ AFLAGS1 ->
+ %% Remove any +IOs
+ AFLAGS2 = list_to_binary(re:replace(AFLAGS1,
+ "\\+IOs (true|false)",
+ "", [global])),
+ [{"ERL_AFLAGS", binary_to_list(AFLAGS2)}]
+ end,
+
+ [PS | _] = get_iostate(""),
+ HaveSchedPoll = proplists:get_value(concurrent_updates, PS),
+
+ 0 = get_sched_pollsets(["+IOs", "false"]),
+ if
+ HaveSchedPoll ->
+ 1 = get_sched_pollsets(["+IOs", "true"]),
+ 1 = get_sched_pollsets([], Env);
+
+ not HaveSchedPoll ->
+ fail = get_sched_pollsets(["+IOs", "true"]),
+ 0 = get_sched_pollsets([], Env)
+ end,
+ fail = get_sched_pollsets(["+IOs", "bad"]),
+ ok.
+
+get_sched_pollsets(Cmd) ->
+ get_sched_pollsets(Cmd, []).
+
+get_sched_pollsets(Cmd, Env)->
+ try
+ {ok, Peer, Node} = ?CT_PEER(#{connection => standard_io, args => Cmd,
+ env => [{"ERL_LIBS", false} | Env]}),
+ [IOStates] = mcall(Node,[fun () -> erlang:system_info(check_io) end]),
+ IO = [IOState || IOState <- IOStates,
+ %% We assume non-fallbacks without threads are scheduler pollsets
+ proplists:get_value(fallback, IOState) == false,
+ proplists:get_value(poll_threads, IOState) == 0],
+ length(IO) % number of scheduler pollsets
+ catch
+ exit:{boot_failed, _} ->
+ fail
+ end.
+
 poll_threads(Config) when is_list(Config) ->
 {Conc, PollType, KP} = get_ioconfig(Config),
 {Sched, SchedOnln, _} = get_sstate(Config, ""),
diff --git a/erts/etc/common/erlexec.c b/erts/etc/common/erlexec.c
index 8dc9363af6..78c4440a3a 100644
--- a/erts/etc/common/erlexec.c
+++ b/erts/etc/common/erlexec.c
@@ -875,6 +875,16 @@ int main(int argc, char **argv)
 i++;
 break;
 }
+ if (argv[i][2] == 'O' && argv[i][3] == 's') {
+ if (argv[i][4] != '\0')
+ goto the_default;
+ NEXT_ARG_CHECK();
+ argv[i][0] = '-';
+ add_Eargs(argv[i]);
+ add_Eargs(argv[i+1]);
+ i++;
+ break;
+ }
 usage(argv[i]);
 break;
 case 'J':
-- 
2.34.1

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File 2224-erts-Add-option-IOs-to-disable-scheduler-polling.patch of Package erlang (Revision e0e016f64b94e78db3440770f914218d)

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