Re: [PATCH net-next] rhashtable: Allow other tasks to be scheduled in large lookup loops

[Eric Dumazet <eric.dumazet@gmail.com>]

On Fri, 2015-07-17 at 10:07 +0200, Thomas Graf wrote:
> Depending on system speed, the large lookup loop can take a considerable
> amount of time to complete causing watchdog warnings to appear. Allow
> other tasks to be scheduled after every batch of 1000 lookups.
> 
> Reported-by: Meelis Roos <mroos@linux.ee>
> Signed-off-by: Thomas Graf <tgraf@suug.ch>
> ---
>  lib/test_rhashtable.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
> index c90777e..5ed6211 100644
> --- a/lib/test_rhashtable.c
> +++ b/lib/test_rhashtable.c
> @@ -20,8 +20,10 @@
>  #include <linux/rcupdate.h>
>  #include <linux/rhashtable.h>
>  #include <linux/slab.h>
> +#include <linux/sched.h>
>  
>  #define MAX_ENTRIES	1000000
> +#define RELAX_CPU_AFTER	1000
>  #define TEST_INSERT_FAIL INT_MAX
>  
>  static int entries = 50000;
> @@ -61,7 +63,7 @@ static struct rhashtable_params test_rht_params = {
>  
>  static int __init test_rht_lookup(struct rhashtable *ht)
>  {
> -	unsigned int i;
> +	unsigned int i, relax_cnt = RELAX_CPU_AFTER;
>  
>  	for (i = 0; i < entries * 2; i++) {
>  		struct test_obj *obj;
> @@ -87,6 +89,11 @@ static int __init test_rht_lookup(struct rhashtable *ht)
>  				return -EINVAL;
>  			}
>  		}
> +
> +		if (!relax_cnt--) {
> +			schedule();
> +			relax_cnt = RELAX_CPU_AFTER;
> +		}
>  	}
>  
>  	return 0;

Please simply use cond_resched() without counting and magic value.