Re: [PATCH] Fixed spam from kni_allocate_mbufs() when no mbufs are free. If mbufs exhausted, 'out of memory' message logged at EXTREMELY high rates. Now logs no more than once per 10 mins

[Stephen Hemminger <stephen-OTpzqLSitTUnbdJkjeBofR2eb7JE58TQ@public.gmane.org>]

On Wed, 17 Dec 2014 07:57:02 -0600
Jay Rolette <rolette-bIuJOMs36aleGPcbtGPokg@public.gmane.org> wrote:

> Signed-off-by: Jay Rolette <rolette-bIuJOMs36aleGPcbtGPokg@public.gmane.org>
> ---
>  lib/librte_kni/rte_kni.c | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_kni/rte_kni.c b/lib/librte_kni/rte_kni.c
> index fdb7509..f89319c 100644
> --- a/lib/librte_kni/rte_kni.c
> +++ b/lib/librte_kni/rte_kni.c
> @@ -40,6 +40,7 @@
>  #include <unistd.h>
>  #include <sys/ioctl.h>
>  
> +#include <rte_cycles.h>
>  #include <rte_spinlock.h>
>  #include <rte_string_fns.h>
>  #include <rte_ethdev.h>
> @@ -61,6 +62,9 @@
>  
>  #define KNI_MEM_CHECK(cond) do { if (cond) goto kni_fail; } while (0)
>  
> +// Configure how often we log "out of memory" messages (in seconds)
> +#define KNI_SPAM_SUPPRESSION_PERIOD 60*10
> +
>  /**
>   * KNI context
>   */
> @@ -592,6 +596,10 @@ kni_free_mbufs(struct rte_kni *kni)
>  static void
>  kni_allocate_mbufs(struct rte_kni *kni)
>  {
> +	static uint64_t no_mbufs = 0;
> +	static uint64_t spam_filter = 0;
> +	static uint64_t delayPeriod = 0;
> +
>  	int i, ret;
>  	struct rte_mbuf *pkts[MAX_MBUF_BURST_NUM];
>  
> @@ -620,7 +628,18 @@ kni_allocate_mbufs(struct rte_kni *kni)
>  		pkts[i] = rte_pktmbuf_alloc(kni->pktmbuf_pool);
>  		if (unlikely(pkts[i] == NULL)) {
>  			/* Out of memory */
> -			RTE_LOG(ERR, KNI, "Out of memory\n");
> +			no_mbufs++;
> +
> +			// Memory leak or need to tune? Regardless, if we get here once,
> +			// we will get here a *lot*. Don't spam the logs!
> +			now = rte_get_tsc_cycles();
> +			if (!delayPeriod)
> +			    delayPeriod = rte_get_tsc_hz() * KNI_SPAM_SUPPRESSION_PERIOD;
> +
> +			if (!spam_filter || (now - spam_filter) > delayPeriod) {
> +				RTE_LOG(ERR, KNI, "No mbufs available (%llu)\n", (unsigned long long)no_mbufs);
> +				spam_filter = now;
> +			}
>  			break;
>  		}
>  	}

I agree whole completely with the intent of this.
But just remove the log message completely. It doesn't
help at all, use a statistic instead.

If you want to do ratelimiting, then it is better to create
a common function (see net_ratelimit() in Linux kernel) to
have all code use the same method, rather than reinventing private
code to do it.

Minor style complaints:
  * don't use camelCase, it goes against the style of the rest of the code.
  * don't use C++ style comments.
  * always use rte_cycles() not TSC for things like this.


Please resubmit removing the log message and adding a statistic.