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-rw-r--r--erts/doc/src/erl.xml36
-rw-r--r--erts/doc/src/erlang.xml19
-rw-r--r--erts/emulator/beam/erl_process.c38
3 files changed, 79 insertions, 14 deletions
diff --git a/erts/doc/src/erl.xml b/erts/doc/src/erl.xml
index bb741c7836..df80142ce1 100644
--- a/erts/doc/src/erl.xml
+++ b/erts/doc/src/erl.xml
@@ -41,6 +41,26 @@
to scroll back to text which has scrolled off the screen.
The <c><![CDATA[erl]]></c> program must be used, however, in pipelines or if
you want to redirect standard input or output.</p>
+ <note><p>As of ERTS version 5.8 (OTP-R14A) the runtime system will by
+ default bind schedulers to logical processors using the
+ <c>default_bind</c> bind type if the amount of schedulers are
+ at least equal to the amount of logical processors configured,
+ binding of schedulers is supported, and a CPU topology is
+ available at startup.
+ </p><p>
+ If the Erlang runtime system is the only operating system
+ process that binds threads to logical processors, this
+ improves the performance of the runtime system. However,
+ if other operating system processes (as for example
+ another Erlang runtime system) also bind threads to
+ logical processors, there might be a performance penalty
+ instead. If this is the case you, are are advised to
+ unbind the schedulers using the
+ <seealso marker="#+sbt">+sbtu</seealso> command line argument,
+ or by invoking
+ <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type,
+ unbound)</seealso>.</p>
+ </note>
</description>
<funcs>
<func>
@@ -657,6 +677,22 @@
that the <c>+sct</c> flag may have to be passed before the
<c>+sbt</c> flag on the command line (in case no CPU topology
has been automatically detected).</p>
+ <p>The runtime system will by default bind schedulers to logical
+ processors using the <c>default_bind</c> bind type if the amount
+ of schedulers are at least equal to the amount of logical
+ processors configured, binding of schedulers is supported,
+ and a CPU topology is available at startup.
+ </p>
+ <p><em>NOTE:</em> If the Erlang runtime system is the only operating
+ system process that binds threads to logical processors, this
+ improves the performance of the runtime system. However, if other
+ operating system processes (as for example another Erlang runtime
+ system) also bind threads to logical processors, there might be a
+ performance penalty instead. If this is the case you, are advised
+ to unbind the schedulers using the <c>+sbtu</c> command line
+ argument, or by invoking
+ <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type,
+ unbound)</seealso>.</p>
<p>For more information, see
<seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, SchedulerBindType)</seealso>.
</p>
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index c3c0dd77d7..c8fe7b4bd2 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -5156,10 +5156,21 @@ true</pre>
For more information on how to define the CPU topology, see
<seealso marker="#system_flag_cpu_topology">erlang:system_flag(cpu_topology, CpuTopology)</seealso>.
</p>
- <p><em>NOTE:</em> If other programs on the system have bound
- to processors, e.g. another Erlang runtime system, you
- may lose performance when binding schedulers. Therefore,
- schedulers are by default not bound.</p>
+ <p>The runtime system will by default bind schedulers to logical
+ processors using the <c>default_bind</c> bind type if the amount
+ of schedulers are at least equal to the amount of logical
+ processors configured, binding of schedulers is supported,
+ and a CPU topology is available at startup.
+ </p>
+ <p><em>NOTE:</em> If the Erlang runtime system is the only
+ operating system process that binds threads to logical processors,
+ this improves the performance of the runtime system. However,
+ if other operating system processes (as for example another Erlang
+ runtime system) also bind threads to logical processors, there
+ might be a performance penalty instead. If this is the case you,
+ are are advised to unbind the schedulers using the
+ <seealso marker="erl#+sbt">+sbtu</seealso> command line argument,
+ or <c>erlang:system_flag(scheduler_bind_type, unbound)</c>.</p>
<p>Schedulers can be bound in different ways. The <c>How</c>
argument determines how schedulers are bound. <c>How</c> can
currently be one of:</p>
diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index e329bfd2d1..c61fab5d36 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -180,6 +180,7 @@ static ErtsCpuBindData *scheduler2cpu_map;
erts_smp_rwmtx_t erts_cpu_bind_rwmtx;
typedef enum {
+ ERTS_CPU_BIND_UNDEFINED,
ERTS_CPU_BIND_SPREAD,
ERTS_CPU_BIND_PROCESSOR_SPREAD,
ERTS_CPU_BIND_THREAD_SPREAD,
@@ -190,6 +191,9 @@ typedef enum {
ERTS_CPU_BIND_NONE
} ErtsCpuBindOrder;
+#define ERTS_CPU_BIND_DEFAULT_BIND \
+ ERTS_CPU_BIND_THREAD_NO_NODE_PROCESSOR_SPREAD
+
ErtsCpuBindOrder cpu_bind_order;
static erts_cpu_topology_t *user_cpudata;
@@ -3503,14 +3507,15 @@ erts_init_scheduler_bind_type(char *how)
if (!system_cpudata && !user_cpudata)
return ERTS_INIT_SCHED_BIND_TYPE_ERROR_NO_CPU_TOPOLOGY;
- if (sys_strcmp(how, "s") == 0)
+ if (sys_strcmp(how, "db") == 0)
+ cpu_bind_order = ERTS_CPU_BIND_DEFAULT_BIND;
+ else if (sys_strcmp(how, "s") == 0)
cpu_bind_order = ERTS_CPU_BIND_SPREAD;
else if (sys_strcmp(how, "ps") == 0)
cpu_bind_order = ERTS_CPU_BIND_PROCESSOR_SPREAD;
else if (sys_strcmp(how, "ts") == 0)
cpu_bind_order = ERTS_CPU_BIND_THREAD_SPREAD;
- else if (sys_strcmp(how, "db") == 0
- || sys_strcmp(how, "tnnps") == 0)
+ else if (sys_strcmp(how, "tnnps") == 0)
cpu_bind_order = ERTS_CPU_BIND_THREAD_NO_NODE_PROCESSOR_SPREAD;
else if (sys_strcmp(how, "nnps") == 0)
cpu_bind_order = ERTS_CPU_BIND_NO_NODE_PROCESSOR_SPREAD;
@@ -4153,14 +4158,15 @@ erts_bind_schedulers(Process *c_p, Eterm how)
old_cpu_bind_order = cpu_bind_order;
- if (ERTS_IS_ATOM_STR("spread", how))
+ if (ERTS_IS_ATOM_STR("default_bind", how))
+ cpu_bind_order = ERTS_CPU_BIND_DEFAULT_BIND;
+ else if (ERTS_IS_ATOM_STR("spread", how))
cpu_bind_order = ERTS_CPU_BIND_SPREAD;
else if (ERTS_IS_ATOM_STR("processor_spread", how))
cpu_bind_order = ERTS_CPU_BIND_PROCESSOR_SPREAD;
else if (ERTS_IS_ATOM_STR("thread_spread", how))
cpu_bind_order = ERTS_CPU_BIND_THREAD_SPREAD;
- else if (ERTS_IS_ATOM_STR("default_bind", how)
- || ERTS_IS_ATOM_STR("thread_no_node_processor_spread", how))
+ else if (ERTS_IS_ATOM_STR("thread_no_node_processor_spread", how))
cpu_bind_order = ERTS_CPU_BIND_THREAD_NO_NODE_PROCESSOR_SPREAD;
else if (ERTS_IS_ATOM_STR("no_node_processor_spread", how))
cpu_bind_order = ERTS_CPU_BIND_NO_NODE_PROCESSOR_SPREAD;
@@ -4206,14 +4212,15 @@ erts_fake_scheduler_bindings(Process *p, Eterm how)
int cpudata_size;
Eterm res;
- if (ERTS_IS_ATOM_STR("spread", how))
+ if (ERTS_IS_ATOM_STR("default_bind", how))
+ fake_cpu_bind_order = ERTS_CPU_BIND_DEFAULT_BIND;
+ else if (ERTS_IS_ATOM_STR("spread", how))
fake_cpu_bind_order = ERTS_CPU_BIND_SPREAD;
else if (ERTS_IS_ATOM_STR("processor_spread", how))
fake_cpu_bind_order = ERTS_CPU_BIND_PROCESSOR_SPREAD;
else if (ERTS_IS_ATOM_STR("thread_spread", how))
fake_cpu_bind_order = ERTS_CPU_BIND_THREAD_SPREAD;
- else if (ERTS_IS_ATOM_STR("default_bind", how)
- || ERTS_IS_ATOM_STR("thread_no_node_processor_spread", how))
+ else if (ERTS_IS_ATOM_STR("thread_no_node_processor_spread", how))
fake_cpu_bind_order = ERTS_CPU_BIND_THREAD_NO_NODE_PROCESSOR_SPREAD;
else if (ERTS_IS_ATOM_STR("no_node_processor_spread", how))
fake_cpu_bind_order = ERTS_CPU_BIND_NO_NODE_PROCESSOR_SPREAD;
@@ -4438,7 +4445,7 @@ early_cpu_bind_init(void)
(sizeof(erts_cpu_topology_t)
* system_cpudata_size));
- cpu_bind_order = ERTS_CPU_BIND_NONE;
+ cpu_bind_order = ERTS_CPU_BIND_UNDEFINED;
if (!erts_get_cpu_topology(erts_cpuinfo, system_cpudata)
|| ERTS_INIT_CPU_TOPOLOGY_OK != verify_topology(system_cpudata,
@@ -4464,6 +4471,17 @@ late_cpu_bind_init(void)
scheduler2cpu_map[ix].bound_id = -1;
}
+ if (cpu_bind_order == ERTS_CPU_BIND_UNDEFINED) {
+ int ncpus = erts_get_cpu_configured(erts_cpuinfo);
+ if (ncpus < 1 || erts_no_schedulers < ncpus)
+ cpu_bind_order = ERTS_CPU_BIND_NONE;
+ else
+ cpu_bind_order = ((system_cpudata || user_cpudata)
+ && (erts_bind_to_cpu(erts_cpuinfo, -1) != -ENOTSUP)
+ ? ERTS_CPU_BIND_DEFAULT_BIND
+ : ERTS_CPU_BIND_NONE);
+ }
+
if (cpu_bind_order != ERTS_CPU_BIND_NONE) {
erts_cpu_topology_t *cpudata;
int cpudata_size;
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-10 14:34:29 +0000