[PATCH v2 2/4] tools/perf: Fix perf bench epoll to correct usage of affinity for machines with #CPUs > 1K

Athira Rajeev
2022-04-06T20:13:49Z

perf bench epoll testcase fails on systems with CPU's
more than 1K.

Testcase: perf bench epoll all
Result snippet:
<<>>
Run summary [PID 106497]: 1399 threads monitoring on 64 file-descriptors for 8 secs.

perf: pthread_create: No such file or directory
<<>>

In epoll benchmarks (ctl, wait) pthread_create is invoked in do_threads
from respective bench_epoll_* function. Though the logs shows direct
failure from pthread_create, the actual failure is from "sched_setaffinity"
returning EINVAL (invalid argument). This happens because the default
mask size in glibc is 1024. To overcome this 1024 CPUs mask size
limitation of cpu_set_t, change the mask size using the CPU_*_S macros.

Patch addresses this by fixing all the epoll benchmarks to use
CPU_ALLOC to allocate cpumask, CPU_ALLOC_SIZE for size, and
CPU_SET_S to set the mask.

Tested-by: Disha Goel <disgoel@linux.vnet.ibm.com>
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Reported-by: Disha Goel <disgoel@linux.vnet.ibm.com>
---
tools/perf/bench/epoll-ctl.c | 25 +++++++++++++++++++------
tools/perf/bench/epoll-wait.c | 25 +++++++++++++++++++------
2 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/tools/perf/bench/epoll-ctl.c b/tools/perf/bench/epoll-ctl.c
index 1a17ec83d3c4..91c53f6c6d87 100644
--- a/tools/perf/bench/epoll-ctl.c
+++ b/tools/perf/bench/epoll-ctl.c
@@ -222,13 +222,20 @@ static void init_fdmaps(struct worker *w, int pct)
static int do_threads(struct worker *worker, struct perf_cpu_map *cpu)
{
pthread_attr_t thread_attr, *attrp = NULL;
- cpu_set_t cpuset;
+ cpu_set_t *cpuset;
unsigned int i, j;
int ret = 0;
+ int nrcpus;
+ size_t size;

if (!noaffinity)
pthread_attr_init(&thread_attr);

+ nrcpus = perf_cpu_map__nr(cpu);
+ cpuset = CPU_ALLOC(nrcpus);
+ BUG_ON(!cpuset);
+ size = CPU_ALLOC_SIZE(nrcpus);
+
for (i = 0; i < nthreads; i++) {
struct worker *w = &worker[i];

@@ -252,22 +259,28 @@ static int do_threads(struct worker *worker, struct perf_cpu_map *cpu)
init_fdmaps(w, 50);

if (!noaffinity) {
- CPU_ZERO(&cpuset);
- CPU_SET(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, &cpuset);
+ CPU_ZERO_S(size, cpuset);
+ CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu,
+ size, cpuset);

- ret = pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset);
- if (ret)
+ ret = pthread_attr_setaffinity_np(&thread_attr, size, cpuset);
+ if (ret) {
+ CPU_FREE(cpuset);
err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
+ }

attrp = &thread_attr;
}

ret = pthread_create(&w->thread, attrp, workerfn,
(void *)(struct worker *) w);
- if (ret)
+ if (ret) {
+ CPU_FREE(cpuset);
err(EXIT_FAILURE, "pthread_create");
+ }
}

+ CPU_FREE(cpuset);
if (!noaffinity)
pthread_attr_destroy(&thread_attr);

diff --git a/tools/perf/bench/epoll-wait.c b/tools/perf/bench/epoll-wait.c
index 0d1dd8879197..9469a53ffab9 100644
--- a/tools/perf/bench/epoll-wait.c
+++ b/tools/perf/bench/epoll-wait.c
@@ -291,9 +291,11 @@ static void print_summary(void)
static int do_threads(struct worker *worker, struct perf_cpu_map *cpu)
{
pthread_attr_t thread_attr, *attrp = NULL;
- cpu_set_t cpuset;
+ cpu_set_t *cpuset;
unsigned int i, j;
int ret = 0, events = EPOLLIN;
+ int nrcpus;
+ size_t size;

if (oneshot)
events |= EPOLLONESHOT;
@@ -306,6 +308,11 @@ static int do_threads(struct worker *worker, struct perf_cpu_map *cpu)
if (!noaffinity)
pthread_attr_init(&thread_attr);

+ nrcpus = perf_cpu_map__nr(cpu);
+ cpuset = CPU_ALLOC(nrcpus);
+ BUG_ON(!cpuset);
+ size = CPU_ALLOC_SIZE(nrcpus);
+
for (i = 0; i < nthreads; i++) {
struct worker *w = &worker[i];

@@ -341,22 +348,28 @@ static int do_threads(struct worker *worker, struct perf_cpu_map *cpu)
}

if (!noaffinity) {
- CPU_ZERO(&cpuset);
- CPU_SET(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, &cpuset);
+ CPU_ZERO_S(size, cpuset);
+ CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu,
+ size, cpuset);

- ret = pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset);
- if (ret)
+ ret = pthread_attr_setaffinity_np(&thread_attr, size, cpuset);
+ if (ret) {
+ CPU_FREE(cpuset);
err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
+ }

attrp = &thread_attr;
}

ret = pthread_create(&w->thread, attrp, workerfn,
(void *)(struct worker *) w);
- if (ret)
+ if (ret) {
+ CPU_FREE(cpuset);
err(EXIT_FAILURE, "pthread_create");
+ }
}

+ CPU_FREE(cpuset);
if (!noaffinity)
pthread_attr_destroy(&thread_attr);

--
2.35.1