[PATCH] hpfall.c improvements, thoughts

[PATCH] hpfall.c improvements, thoughts

[Christian Thaeter]

Some conversation I had with Pavel,

imo the example code should be at least barely useable as in not causing
harm like I sketched in (1.). Maybe someone else picks that up and
improves it later on. Patch at the end, quite sketchy and imature as it
doesn't check for errors, but certainly better than before.


	Christian


Pavel Machek wrote:
> Hi!
> 
>> I just hacked and installed the hpfall utility a little bit. By that I
>> thought I should share some ideas with you. (made no patch since this is
>> trivial, but important)
>>
>> 1. hpfall *MUST* mlockall(MCL_CURRENT|MCL_FUTURE); itself!
>> Since the Program sits and waits most of the time it becomes very likely
>> swapped out. If it gets woken up when the laptop drops from the table
>> while it is swapped out it actually triggers harddrive activity!
>>
>> 2. daemon(0, 0);  ... Quick and dirty way to daemonize it
>>
>> 3. Realtime priority:
>>  param.sched_priority = sched_get_priority_max(SCHED_FIFO);
>>  sched_setscheduler(0, SCHED_FIFO, &param);
>> Should give a chance that it has less latency when woken up.
> 
> Good ideas. I ommited them, thinking that someone else will do it. Can
> you submit a patch? (akpm, cc: lk, Eric Piel) I no longer have the
> hardware, and would prefer not to patch code I can't test.
> 
>> .. another thing is that I still use the old IDE driver, I just changed
>> sda to hda, maybe a bandaid is to use argv[1] for defining the drive
>> (well I understand that it is very basic example code, so maybe someday
>> someone adds a better option parser)
> 
> Option parser would indeed be nice.
> 								Pavel
>


Signed-off-by: Christian Thaeter <ct@pipapo.org>
---

diff --git a/Documentation/hwmon/hpfall.c b/Documentation/hwmon/hpfall.c
index bbea1cc..f3cde67 100644
--- a/Documentation/hwmon/hpfall.c
+++ b/Documentation/hwmon/hpfall.c
@@ -16,6 +16,8 @@
 #include <stdint.h>
 #include <errno.h>
 #include <signal.h>
+#include <sys/mman.h>
+#include <sched.h>

 void write_int(char *path, int i)
 {
@@ -63,6 +65,7 @@ void ignore_me(void)
 int main(int argc, char* argv[])
 {
        int fd, ret;
+       struct sched_param param;

        fd = open("/dev/freefall", O_RDONLY);
        if (fd < 0) {
@@ -70,7 +73,12 @@ int main(int argc, char* argv[])
                return EXIT_FAILURE;
        }

-	signal(SIGALRM, ignore_me);
+       daemon(0,0);
+       param.sched_priority = sched_get_priority_max(SCHED_FIFO);
+       sched_setscheduler(0, SCHED_FIFO, &param);
+       mlockall(MCL_CURRENT|MCL_FUTURE);
+
+       signal(SIGALRM, ignore_me);

        for (;;) {
 	       unsigned char count;

Re: [PATCH] hpfall.c improvements, thoughts

[Pavel Machek]

Hi!

> Some conversation I had with Pavel,
> 
> imo the example code should be at least barely useable as in not causing
> harm like I sketched in (1.). Maybe someone else picks that up and
> improves it later on. Patch at the end, quite sketchy and imature as it
> doesn't check for errors, but certainly better than before.

Thanks. Acked-by: Pavel Machek <pavel@ucw.cz>
									Pavel


> Signed-off-by: Christian Thaeter <ct@pipapo.org>
> ---
> 
> diff --git a/Documentation/hwmon/hpfall.c b/Documentation/hwmon/hpfall.c
> index bbea1cc..f3cde67 100644
> --- a/Documentation/hwmon/hpfall.c
> +++ b/Documentation/hwmon/hpfall.c
> @@ -16,6 +16,8 @@
>  #include <stdint.h>
>  #include <errno.h>
>  #include <signal.h>
> +#include <sys/mman.h>
> +#include <sched.h>
> 
>  void write_int(char *path, int i)
>  {
> @@ -63,6 +65,7 @@ void ignore_me(void)
>  int main(int argc, char* argv[])
>  {
>         int fd, ret;
> +       struct sched_param param;
> 
>         fd = open("/dev/freefall", O_RDONLY);
>         if (fd < 0) {
> @@ -70,7 +73,12 @@ int main(int argc, char* argv[])
>                 return EXIT_FAILURE;
>         }
> 
> -	signal(SIGALRM, ignore_me);
> +       daemon(0,0);
> +       param.sched_priority = sched_get_priority_max(SCHED_FIFO);
> +       sched_setscheduler(0, SCHED_FIFO, &param);
> +       mlockall(MCL_CURRENT|MCL_FUTURE);
> +
> +       signal(SIGALRM, ignore_me);
> 
>         for (;;) {
>  	       unsigned char count;

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH] hpfall.c improvements, thoughts

[Éric Piel]

Op 25-03-09 22:27, Christian Thaeter schreef:
> Some conversation I had with Pavel,
> 
> imo the example code should be at least barely useable as in not causing
> harm like I sketched in (1.). Maybe someone else picks that up and
> improves it later on. Patch at the end, quite sketchy and imature as it
> doesn't check for errors, but certainly better than before.
> 
Hello Christian,
Would you mind resending the patch with a changelog, so that Andrew can
merge it?

Thanks,
Eric

> 
> Signed-off-by: Christian Thaeter <ct@pipapo.org>
Acked-by: Éric Piel <eric.piel@tremplin-utc.net>

> ---
> 
> diff --git a/Documentation/hwmon/hpfall.c b/Documentation/hwmon/hpfall.c
> index bbea1cc..f3cde67 100644
> --- a/Documentation/hwmon/hpfall.c
> +++ b/Documentation/hwmon/hpfall.c
> @@ -16,6 +16,8 @@
>  #include <stdint.h>
>  #include <errno.h>
>  #include <signal.h>
> +#include <sys/mman.h>
> +#include <sched.h>
> 
>  void write_int(char *path, int i)
>  {
> @@ -63,6 +65,7 @@ void ignore_me(void)
>  int main(int argc, char* argv[])
>  {
>         int fd, ret;
> +       struct sched_param param;
> 
>         fd = open("/dev/freefall", O_RDONLY);
>         if (fd < 0) {
> @@ -70,7 +73,12 @@ int main(int argc, char* argv[])
>                 return EXIT_FAILURE;
>         }
> 
> -	signal(SIGALRM, ignore_me);
> +       daemon(0,0);
> +       param.sched_priority = sched_get_priority_max(SCHED_FIFO);
> +       sched_setscheduler(0, SCHED_FIFO, &param);
> +       mlockall(MCL_CURRENT|MCL_FUTURE);
> +
> +       signal(SIGALRM, ignore_me);
> 
>         for (;;) {
>  	       unsigned char count;