[LTP] [PATCH 1/1] tst_pids.c: fix fork failure on small memory systems

[LTP] [PATCH 1/1] tst_pids.c: fix fork failure on small memory systems

[Leo Yu-Chi Liang]

Running syscalls/msgstress03 on a system with less than ~1 GB of RAM fails:

	msgstress03    1  TFAIL  :  msgstress03.c:163:  Fork failed (may be OK if under stress)

The reason is that besides /proc/sys/kernel/pid_max, /proc/sys/kernel/threads-max
is another factor determining how many processes a system could create.

Use the smaller number between pid_max and threads-max as the nprocs.

Signed-off-by: Leo Yu-Chi Liang <ycliang@andestech.com>
---
 lib/tst_pid.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/tst_pid.c b/lib/tst_pid.c
index 21cadef2a..3fb3f39ad 100644
--- a/lib/tst_pid.c
+++ b/lib/tst_pid.c
@@ -31,6 +31,7 @@
 #include "tst_safe_macros.h"
 
 #define PID_MAX_PATH "/proc/sys/kernel/pid_max"
+#define THREADS_MAX_PATH "/proc/sys/kernel/threads-max"
 #define CGROUPS_V1_SLICE_FMT "/sys/fs/cgroup/pids/user.slice/user-%d.slice/pids.max"
 #define CGROUPS_V2_SLICE_FMT "/sys/fs/cgroup/user.slice/user-%d.slice/pids.max"
 /* Leave some available processes for the OS */
@@ -113,7 +114,7 @@ static int get_session_pids_limit(void (*cleanup_fn) (void))
 int tst_get_free_pids_(void (*cleanup_fn) (void))
 {
 	FILE *f;
-	int rc, used_pids, max_pids, max_session_pids;
+	int rc, used_pids, max_pids, max_session_pids, max_threads;
 
 	f = popen("ps -eT | wc -l", "r");
 	if (!f) {
@@ -129,6 +130,8 @@ int tst_get_free_pids_(void (*cleanup_fn) (void))
 	}
 
 	SAFE_FILE_SCANF(cleanup_fn, PID_MAX_PATH, "%d", &max_pids);
+	SAFE_FILE_SCANF(cleanup_fn, THREADS_MAX_PATH, "%d", &max_threads);
+	max_pids = (max_pids < max_threads) ? max_pids : max_threads;
 
 	max_session_pids = get_session_pids_limit(cleanup_fn);
 	if ((max_session_pids > 0) && (max_session_pids < max_pids))
-- 
2.34.1


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Re: [LTP] [PATCH 1/1] tst_pids.c: fix fork failure on small memory systems

[Petr Vorel]

Hi Leo,

> Running syscalls/msgstress03 on a system with less than ~1 GB of RAM fails:

> 	msgstress03    1  TFAIL  :  msgstress03.c:163:  Fork failed (may be OK if under stress)

> The reason is that besides /proc/sys/kernel/pid_max, /proc/sys/kernel/threads-max
> is another factor determining how many processes a system could create.

> Use the smaller number between pid_max and threads-max as the nprocs.

Makes sense.
Reviewed-by: Petr Vorel <pvorel@suse.cz>

BTW IMHO it'd be better to rewrite
f = popen("ps -eT | wc -l", "r");
to list count of /proc/[0-9]*/ in plain C (TODO for us).

Kind regards,
Petr

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Re: [LTP] [PATCH 1/1] tst_pids.c: fix fork failure on small memory systems

[Jan Stancek]

On Tue, Feb 7, 2023 at 2:42 PM Petr Vorel <pvorel@suse.cz> wrote:
>
> Hi Leo,
>
> > Running syscalls/msgstress03 on a system with less than ~1 GB of RAM fails:
>
> >       msgstress03    1  TFAIL  :  msgstress03.c:163:  Fork failed (may be OK if under stress)
>
> > The reason is that besides /proc/sys/kernel/pid_max, /proc/sys/kernel/threads-max
> > is another factor determining how many processes a system could create.
>
> > Use the smaller number between pid_max and threads-max as the nprocs.
>
> Makes sense.
> Reviewed-by: Petr Vorel <pvorel@suse.cz>
>

Acked-by: Jan Stancek <jstancek@redhat.com>


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Re: [LTP] [PATCH 1/1] tst_pids.c: fix fork failure on small memory systems

[Cyril Hrubis]

Hi!
>  lib/tst_pid.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/tst_pid.c b/lib/tst_pid.c
> index 21cadef2a..3fb3f39ad 100644
> --- a/lib/tst_pid.c
> +++ b/lib/tst_pid.c
> @@ -31,6 +31,7 @@
>  #include "tst_safe_macros.h"
>  
>  #define PID_MAX_PATH "/proc/sys/kernel/pid_max"
> +#define THREADS_MAX_PATH "/proc/sys/kernel/threads-max"
>  #define CGROUPS_V1_SLICE_FMT "/sys/fs/cgroup/pids/user.slice/user-%d.slice/pids.max"
>  #define CGROUPS_V2_SLICE_FMT "/sys/fs/cgroup/user.slice/user-%d.slice/pids.max"
>  /* Leave some available processes for the OS */
> @@ -113,7 +114,7 @@ static int get_session_pids_limit(void (*cleanup_fn) (void))
>  int tst_get_free_pids_(void (*cleanup_fn) (void))
>  {
>  	FILE *f;
> -	int rc, used_pids, max_pids, max_session_pids;
> +	int rc, used_pids, max_pids, max_session_pids, max_threads;
>  
>  	f = popen("ps -eT | wc -l", "r");
>  	if (!f) {
> @@ -129,6 +130,8 @@ int tst_get_free_pids_(void (*cleanup_fn) (void))
>  	}
>  
>  	SAFE_FILE_SCANF(cleanup_fn, PID_MAX_PATH, "%d", &max_pids);
> +	SAFE_FILE_SCANF(cleanup_fn, THREADS_MAX_PATH, "%d", &max_threads);
> +	max_pids = (max_pids < max_threads) ? max_pids : max_threads;

BTW: We do have a MIN() macro definition in tst_minmax.h header so we
     can just do max_pids = MIN(max_pids, max_threads);

>  	max_session_pids = get_session_pids_limit(cleanup_fn);
>  	if ((max_session_pids > 0) && (max_session_pids < max_pids))

Otherwise:

Reviewed-by: Cyril Hrubis <chrubis@suse.cz>

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Cyril Hrubis
chrubis@suse.cz

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Re: [LTP] [PATCH 1/1] tst_pids.c: fix fork failure on small memory systems

[Leo Liang]

Hi Petr,

On Tue, Feb 07, 2023 at 02:42:22PM +0100, Petr Vorel wrote:
> Hi Leo,
> 
> > Running syscalls/msgstress03 on a system with less than ~1 GB of RAM fails:
> 
> > 	msgstress03    1  TFAIL  :  msgstress03.c:163:  Fork failed (may be OK if under stress)
> 
> > The reason is that besides /proc/sys/kernel/pid_max, /proc/sys/kernel/threads-max
> > is another factor determining how many processes a system could create.
> 
> > Use the smaller number between pid_max and threads-max as the nprocs.
> 
> Makes sense.
> Reviewed-by: Petr Vorel <pvorel@suse.cz>
> 
> BTW IMHO it'd be better to rewrite
> f = popen("ps -eT | wc -l", "r");
> to list count of /proc/[0-9]*/ in plain C (TODO for us).
>

Thanks for the review!
I could send a v2 to add this as well.

Best regards,
Leo

> Kind regards,
> Petr

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Re: [LTP] [PATCH 1/1] tst_pids.c: fix fork failure on small memory systems

[Leo Liang]

Hi Cyril,

On Thu, Feb 09, 2023 at 02:05:46PM +0100, Cyril Hrubis wrote:
> Hi!
> >  lib/tst_pid.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/lib/tst_pid.c b/lib/tst_pid.c
> > index 21cadef2a..3fb3f39ad 100644
> > --- a/lib/tst_pid.c
> > +++ b/lib/tst_pid.c
> > @@ -31,6 +31,7 @@
> >  #include "tst_safe_macros.h"
> >  
> >  #define PID_MAX_PATH "/proc/sys/kernel/pid_max"
> > +#define THREADS_MAX_PATH "/proc/sys/kernel/threads-max"
> >  #define CGROUPS_V1_SLICE_FMT "/sys/fs/cgroup/pids/user.slice/user-%d.slice/pids.max"
> >  #define CGROUPS_V2_SLICE_FMT "/sys/fs/cgroup/user.slice/user-%d.slice/pids.max"
> >  /* Leave some available processes for the OS */
> > @@ -113,7 +114,7 @@ static int get_session_pids_limit(void (*cleanup_fn) (void))
> >  int tst_get_free_pids_(void (*cleanup_fn) (void))
> >  {
> >  	FILE *f;
> > -	int rc, used_pids, max_pids, max_session_pids;
> > +	int rc, used_pids, max_pids, max_session_pids, max_threads;
> >  
> >  	f = popen("ps -eT | wc -l", "r");
> >  	if (!f) {
> > @@ -129,6 +130,8 @@ int tst_get_free_pids_(void (*cleanup_fn) (void))
> >  	}
> >  
> >  	SAFE_FILE_SCANF(cleanup_fn, PID_MAX_PATH, "%d", &max_pids);
> > +	SAFE_FILE_SCANF(cleanup_fn, THREADS_MAX_PATH, "%d", &max_threads);
> > +	max_pids = (max_pids < max_threads) ? max_pids : max_threads;
> 
> BTW: We do have a MIN() macro definition in tst_minmax.h header so we
>      can just do max_pids = MIN(max_pids, max_threads);
> 

Thanks for the review!
Will send a v2 to fix this!

Best regards,
Leo

> >  	max_session_pids = get_session_pids_limit(cleanup_fn);
> >  	if ((max_session_pids > 0) && (max_session_pids < max_pids))
> 
> Otherwise:
> 
> Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
> 
> -- 
> Cyril Hrubis
> chrubis@suse.cz

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Re: [LTP] [PATCH 1/1] tst_pids.c: fix fork failure on small memory systems

[Petr Vorel]

Hi all,

Thanks Leo, I merged it with MIN(max_pids, max_threads), thanks Cyril for
catching it.

> > BTW IMHO it'd be better to rewrite
> > f = popen("ps -eT | wc -l", "r");
> > to list count of /proc/[0-9]*/ in plain C (TODO for us).


> Thanks for the review!
> I could send a v2 to add this as well.

Thank you, if you have time to send another patch to fix.

Kind regards,
Petr

> Best regards,
> Leo

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