diff mbox series

[v3,7/7] fzsync: Check processor affinity

Message ID 20210319091837.27319-8-rpalethorpe@suse.com
State Superseded
Headers show
Series Fuzzy Sync single core support and tests | expand

Commit Message

Richard Palethorpe March 19, 2021, 9:18 a.m. UTC 
It is useful for testing Fuzzy Sync itself to set the CPU affinity to
a single core. The current processes affinity does not effect
tst_ncpus(), but we can get the affinity separately.

Note that checking this still does not guarantee we will use yield
when restricted to only one core. We would have to periodically probe
which CPUs threads are running on until we detect more than one CPU.

Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
---
 include/tst_fuzzy_sync.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Comments

Cyril Hrubis April 8, 2021, 12:47 p.m. UTC | #1 
Hi!
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>

The patchset that fixes fuzzy sync on single CPU seems to be good to go,
I will have a look at the self tests now.
Li Wang April 9, 2021, 7:18 a.m. UTC | #2 
static void tst_fzsync_pair_init(struct tst_fzsync_pair *pair)
>  {
> +       long ncpus = tst_ncpus_available();
> +
>         CHK(avg_alpha, 0, 1, 0.25);
>         CHK(min_samples, 20, INT_MAX, 1024);
>         CHK(max_dev_ratio, 0, 1, 0.1);
>         CHK(exec_time_p, 0, 1, 0.5);
>         CHK(exec_loops, 20, INT_MAX, 3000000);
> -       CHK(yield_in_wait, 0, 1, (tst_ncpus() <= 1));
> +
> +       if (ncpus <= 1)
> +               pair->yield_in_wait = 1;
>

I'm wondering here why not using the CHK macro as before but additionally
involved a variable 'ncpus'.

Isn't that CHK(yield_in_wait, 0, 1, (tst_ncpus_available() <= 1)) better?
Richard Palethorpe April 9, 2021, 9:50 a.m. UTC | #3 
Hello Li,

Li Wang <liwang@redhat.com> writes:

>  static void tst_fzsync_pair_init(struct tst_fzsync_pair *pair)
>>  {
>> +       long ncpus = tst_ncpus_available();
>> +
>>         CHK(avg_alpha, 0, 1, 0.25);
>>         CHK(min_samples, 20, INT_MAX, 1024);
>>         CHK(max_dev_ratio, 0, 1, 0.1);
>>         CHK(exec_time_p, 0, 1, 0.5);
>>         CHK(exec_loops, 20, INT_MAX, 3000000);
>> -       CHK(yield_in_wait, 0, 1, (tst_ncpus() <= 1));
>> +
>> +       if (ncpus <= 1)
>> +               pair->yield_in_wait = 1;
>>
>
> I'm wondering here why not using the CHK macro as before but additionally
> involved a variable 'ncpus'.
>
> Isn't that CHK(yield_in_wait, 0, 1, (tst_ncpus_available() <= 1)) better?

The macro generates compiler warnings because yield_in_wait is bool and
so it is always inside the valid range unless (ncpus <= 1).

However I should remove the useless variable.
diff mbox series

Patch

diff --git a/include/tst_fuzzy_sync.h b/include/tst_fuzzy_sync.h
index 36a604e13..e38b56e5e 100644
--- a/include/tst_fuzzy_sync.h
+++ b/include/tst_fuzzy_sync.h
@@ -61,7 +61,6 @@ 
 
 #include <math.h>
 #include <pthread.h>
-#include <sched.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <sys/time.h>
@@ -213,12 +212,16 @@  struct tst_fzsync_pair {
  */
 static void tst_fzsync_pair_init(struct tst_fzsync_pair *pair)
 {
+	long ncpus = tst_ncpus_available();
+
 	CHK(avg_alpha, 0, 1, 0.25);
 	CHK(min_samples, 20, INT_MAX, 1024);
 	CHK(max_dev_ratio, 0, 1, 0.1);
 	CHK(exec_time_p, 0, 1, 0.5);
 	CHK(exec_loops, 20, INT_MAX, 3000000);
-	CHK(yield_in_wait, 0, 1, (tst_ncpus() <= 1));
+
+	if (ncpus <= 1)
+		pair->yield_in_wait = 1;
 }
 #undef CHK