sched_getaffinity() and pthread_getaffinity_np() do not return
an accurate mask of all CPUs in the machine when the kernel
is compiled with NO_HZ_FULL support.
See Linaro BUG 2027 for details.
https://bugs.linaro.org/show_bug.cgi?id=2027
This code replaces the 'getaffinity' based CPU discovery logic
-and- removes any exclusivity between default control and worker
cpumasks, based on an assumption that external cpumask specifications
will segregate CPUs if needed.
The results of these changes which address BUG 2027 are:
(1) all CPUs known to the kernel at boot time are considered
for use by ODP regardless of the default CPU affinity masks
set by the kernel scheduler,
(2) the default control and worker cpumasks are given reasonable
values based on the set of installed CPUs
Also - this code:
(a) adds control and worker cpumasks to the linux-generic global data
(b) adds logic to odp_cpumask.c to initialize these masks
(c) calls the new cpumask initialization logic from odp_init_global()
(d) reduces odp_cpumask_default_control() and
odp_cpumask_default_worker() to use the content of these new
cpumasks without modification.
These changes provide prerequisite infrastructure for pending changes
which will allow ODP to accept cpumasks passed in
from external entities such as a provisioning service.
Signed-off-by: Gary S. Robertson <gary.robert...@linaro.org>
---
platform/linux-generic/include/odp_internal.h | 7 ++
platform/linux-generic/odp_cpumask.c | 126 ++++++++++++++++++++++++++
platform/linux-generic/odp_cpumask_task.c | 70 +++++++++-----
platform/linux-generic/odp_init.c | 9 +-
platform/linux-generic/odp_system_info.c | 13 +--
5 files changed, 187 insertions(+), 38 deletions(-)
diff --git a/platform/linux-generic/include/odp_internal.h
b/platform/linux-generic/include/odp_internal.h
index 679d9d2..567b1fb 100644
--- a/platform/linux-generic/include/odp_internal.h
+++ b/platform/linux-generic/include/odp_internal.h
@@ -18,6 +18,7 @@ extern "C" {
#endif
#include <odp/api/init.h>
+#include <odp/api/cpumask.h>
#include <odp/api/thread.h>
#include <stdio.h>
@@ -40,6 +41,9 @@ struct odp_global_data_s {
odp_log_func_t log_fn;
odp_abort_func_t abort_fn;
odp_system_info_t system_info;
+ odp_cpumask_t control_cpus;
+ odp_cpumask_t worker_cpus;
+ int num_cpus_installed;
};
enum init_stage {
@@ -65,6 +69,9 @@ extern struct odp_global_data_s odp_global_data;
int _odp_term_global(enum init_stage stage);
int _odp_term_local(enum init_stage stage);
+int odp_cpumask_init_global(void);
+int odp_cpumask_term_global(void);
+
int odp_system_info_init(void);
int odp_system_info_term(void);
diff --git a/platform/linux-generic/odp_cpumask.c
b/platform/linux-generic/odp_cpumask.c
index 4249f1d..320ca8e 100644
--- a/platform/linux-generic/odp_cpumask.c
+++ b/platform/linux-generic/odp_cpumask.c
@@ -15,6 +15,10 @@
#include <stdlib.h>
#include <string.h>
+#include <dirent.h>
+#include <errno.h>
+#include <sys/types.h>
+
/** @internal Compile time assert */
_ODP_STATIC_ASSERT(CPU_SETSIZE >= ODP_CPUMASK_SIZE,
"ODP_CPUMASK_SIZE__SIZE_ERROR");
@@ -208,3 +212,125 @@ int odp_cpumask_next(const odp_cpumask_t *mask, int cpu)
return cpu;
return -1;
}
+
+/*
+ * This function obtains system information specifying which cpus are
+ * available at boot time. These data are then used to produce cpumasks of
+ * configured CPUs without concern over isolation support.
+ */
+static int get_installed_cpus(void)
+{
+ char *numptr;
+ char *endptr;
+ long int cpu_idnum;
+ DIR *d;
+ struct dirent *dir;
+
+ /* Clear the global cpumasks for control and worker CPUs */
+ odp_cpumask_zero(&odp_global_data.control_cpus);
+ odp_cpumask_zero(&odp_global_data.worker_cpus);
+
+ /*
+ * Scan the /sysfs pseudo-filesystem for CPU info directories.
+ * There should be one subdirectory for each installed logical CPU
+ */
+ d = opendir("/sys/devices/system/cpu");
+ if (d) {
+ while ((dir = readdir(d)) != NULL) {
+ cpu_idnum = CPU_SETSIZE;
+
+ /*
+ * If the current directory entry doesn't represent
+ * a CPU info subdirectory then skip to the next entry.
+ */
+ if (dir->d_type == DT_DIR) {
+ if (!strncmp(dir->d_name, "cpu", 3)) {
+ /*
+ * Directory name starts with "cpu"...
+ * Try to extract a CPU ID number
+ * from the remainder of the dirname.
+ */
+ errno = 0;
+ numptr = dir->d_name;
+ numptr += 3;
+ cpu_idnum = strtol(numptr, &endptr,
+ 10);
+ if (errno || (endptr == numptr))
+ continue;
+ } else {
+ continue;
+ }
+ } else {
+ continue;
+ }
+ /*
+ * If we get here the current directory entry specifies
+ * a CPU info subdir for the CPU indexed by cpu_idnum.
+ */
+
+ /* Track number of logical CPUs discovered */
+ if (odp_global_data.num_cpus_installed <
+ (int)(cpu_idnum + 1))
+ odp_global_data.num_cpus_installed =
+ (int)(cpu_idnum + 1);
+
+ /* Add the CPU to our default cpumasks */
+ odp_cpumask_set(&odp_global_data.control_cpus,
+ (int)cpu_idnum);
+ odp_cpumask_set(&odp_global_data.worker_cpus,
+ (int)cpu_idnum);
+ }
+ closedir(d);
+ return 0;
+ } else {
+ return -1;
+ }
+}
+
+/*
+ * This function creates reasonable default cpumasks for control and worker
+ * tasks from the set of CPUs available at boot time.
+ */
+int odp_cpumask_init_global(void)
+{
+ odp_cpumask_t *control_mask = &odp_global_data.control_cpus;
+ odp_cpumask_t *worker_mask = &odp_global_data.worker_cpus;
+ int i;
+ int retval = -1;
+
+ if (!get_installed_cpus()) {
+ /* CPU 0 is only used for workers on uniprocessor systems */
+ if (odp_global_data.num_cpus_installed > 1)
+ odp_cpumask_clr(worker_mask, 0);
+ /*
+ * If only one or two CPUs installed, use CPU 0 for control.
+ * Otherwise leave it for the kernel and start with CPU 1.
+ */
+ if (odp_global_data.num_cpus_installed < 3) {
+ /*
+ * If only two CPUS, use CPU 0 for control and
+ * use CPU 1 for workers.
+ */
+ odp_cpumask_clr(control_mask, 1);
+ } else {
+ /*
+ * If three or more CPUs, reserve CPU 0 for kernel,
+ * reserve CPU 1 for control, and
+ * reserve remaining CPUs for workers
+ */
+ odp_cpumask_clr(control_mask, 0);
+ odp_cpumask_clr(worker_mask, 1);
+ for (i = 2; i < CPU_SETSIZE; i++) {
+ if (odp_cpumask_isset(worker_mask, i))
+ odp_cpumask_clr(control_mask, i);
+ }
+ }
+ retval = 0;
+ }
+ return retval;
+}
+
+int odp_cpumask_term_global(void)
+{
+ return 0;
+}
diff --git a/platform/linux-generic/odp_cpumask_task.c
b/platform/linux-generic/odp_cpumask_task.c
index dbedff2..10885ce 100644
--- a/platform/linux-generic/odp_cpumask_task.c
+++ b/platform/linux-generic/odp_cpumask_task.c
@@ -14,53 +14,75 @@
int odp_cpumask_default_worker(odp_cpumask_t *mask, int num)
{
- int ret, cpu, i;
- cpu_set_t cpuset;
-
- ret = pthread_getaffinity_np(pthread_self(),
- sizeof(cpu_set_t), &cpuset);
- if (ret != 0)
- ODP_ABORT("failed to read CPU affinity value\n");
-
- odp_cpumask_zero(mask);
+ odp_cpumask_t overlap;
+ int cpu, i;
/*
* If no user supplied number or it's too large, then attempt
* to use all CPUs
*/
- if (0 == num || CPU_SETSIZE < num)
- num = CPU_COUNT(&cpuset);
+ cpu = odp_cpumask_count(&odp_global_data.worker_cpus);
+ if (0 == num || cpu < num)
+ num = cpu;
/* build the mask, allocating down from highest numbered CPU */
+ odp_cpumask_zero(mask);
for (cpu = 0, i = CPU_SETSIZE - 1; i >= 0 && cpu < num; --i) {
- if (CPU_ISSET(i, &cpuset)) {
+ if (odp_cpumask_isset(&odp_global_data.worker_cpus, i)) {
odp_cpumask_set(mask, i);
cpu++;
}
}
- if (odp_cpumask_isset(mask, 0))
- ODP_DBG("\n\tCPU0 will be used for both control and worker
threads,\n"
- "\tthis will likely have a performance impact on the
worker thread.\n");
+ odp_cpumask_and(&overlap, mask, &odp_global_data.control_cpus);
+ if (odp_cpumask_count(&overlap))
+ ODP_DBG("\n\tWorker CPUs overlap with control CPUs...\n"
+ "\tthis will likely have a performance impact on the
worker threads.\n");
return cpu;
}
-int odp_cpumask_default_control(odp_cpumask_t *mask, int num ODP_UNUSED)
+int odp_cpumask_default_control(odp_cpumask_t *mask, int num)
{
+ odp_cpumask_t overlap;
+ int cpu, i;
+
+ /*
+ * If no user supplied number then default to one control CPU.
+ */
+ if (0 == num) {
+ num = 1;
+ } else {
+ /*
+ * If user supplied number is too large, then attempt
+ * to use all installed control CPUs
+ */
+ cpu = odp_cpumask_count(&odp_global_data.control_cpus);
+ if (cpu < num)
+ num = cpu;
+ }
+
+ /* build the mask, allocating upwards from lowest numbered CPU */
odp_cpumask_zero(mask);
- /* By default all control threads on CPU 0 */
- odp_cpumask_set(mask, 0);
- return 1;
+ for (cpu = 0, i = 0; i < CPU_SETSIZE && cpu < num; i++) {
+ if (odp_cpumask_isset(&odp_global_data.control_cpus, i)) {
+ odp_cpumask_set(mask, i);
+ cpu++;
+ }
+ }
+
+ odp_cpumask_and(&overlap, mask, &odp_global_data.worker_cpus);
+ if (odp_cpumask_count(&overlap))
+ ODP_DBG("\n\tControl CPUs overlap with worker CPUs...\n"
+ "\tthis will likely have a performance impact on the
worker threads.\n");
+
+ return cpu;
}
int odp_cpumask_all_available(odp_cpumask_t *mask)
{
- odp_cpumask_t mask_work, mask_ctrl;
-
- odp_cpumask_default_worker(&mask_work, 0);
- odp_cpumask_default_control(&mask_ctrl, 0);
- odp_cpumask_or(mask, &mask_work, &mask_ctrl);
+ odp_cpumask_or(mask, &odp_global_data.worker_cpus,
+ &odp_global_data.control_cpus);
return odp_cpumask_count(mask);
}
diff --git a/platform/linux-generic/odp_init.c
b/platform/linux-generic/odp_init.c
index f30c310..d1b86ad 100644
--- a/platform/linux-generic/odp_init.c
+++ b/platform/linux-generic/odp_init.c
@@ -3,11 +3,9 @@
*
* SPDX-License-Identifier: BSD-3-Clause
*/
-
#include <odp/api/init.h>
-#include <odp_internal.h>
-#include <odp/api/debug.h>
#include <odp_debug_internal.h>
+#include <odp/api/debug.h>
struct odp_global_data_s odp_global_data;
@@ -26,6 +24,11 @@ int odp_init_global(odp_instance_t *instance,
odp_global_data.abort_fn = params->abort_fn;
}
+ if (odp_cpumask_init_global()) {
+ ODP_ERR("ODP cpumask init failed.\n");
+ goto init_failed;
+ }
+
if (odp_time_init_global()) {
ODP_ERR("ODP time init failed.\n");
goto init_failed;
diff --git a/platform/linux-generic/odp_system_info.c
b/platform/linux-generic/odp_system_info.c
index 395b274..1ecf18a 100644
--- a/platform/linux-generic/odp_system_info.c
+++ b/platform/linux-generic/odp_system_info.c
@@ -30,21 +30,12 @@
#define HUGE_PAGE_DIR "/sys/kernel/mm/hugepages"
-
/*
- * Report the number of CPUs in the affinity mask of the main thread
+ * Report the number of logical CPUs detected at boot time
*/
static int sysconf_cpu_count(void)
{
- cpu_set_t cpuset;
- int ret;
-
- ret = pthread_getaffinity_np(pthread_self(),
- sizeof(cpuset), &cpuset);
- if (ret != 0)
- return 0;
-
- return CPU_COUNT(&cpuset);
+ return odp_global_data.num_cpus_installed;
}
#if defined __x86_64__ || defined __i386__ || defined __OCTEON__ || \
--
1.9.1
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