On Thu, 2008-09-04 at 14:18 -0700, Stephen Hemminger wrote:
> Reduce snmpd memory usage.
>
> The route table can grow very large and existing code is a major
> performance problem since it wastes half of its memory and copies
> each time.
>
> 1. Grow expanding table by 1.5 rather 2x per step
You need to make sure that the table grows at all.
Additionally, at the moment the table never shrinks, I think that is a
obvious potential improvment for memory usage.
> Perhaps the increment should just be PAGESIZE
This is interesting - the effect is that it changes the insert from O(n)
to O(n*n) but for small tables I think it would be a gain anyway and you
do avoid the problem of the big growth.
> 2. Use realloc rather than copying, this allows for possible
> inplace growth and smart allocation.
This I think sounds like an excellent idea and it do lessen some of the
+PAGESIZE cost.
> --- a/snmplib/container_binary_array.c 2008-09-04 11:47:25.000000000
> -0700
> +++ b/snmplib/container_binary_array.c 2008-09-04 12:26:14.000000000
> -0700
> @@ -357,19 +357,15 @@ netsnmp_binary_array_insert(netsnmp_cont
> /*
> * Table is full, so extend it to double the size
> */
> - new_max = 2 * t->max_size;
> + new_max = t->max_size + t->max_size / 2;
> if (new_max == 0)
> new_max = 10; /* Start with 10 entries */
>
> - new_data = (void *) calloc(new_max, t->data_size);
> + new_data = realloc(t->data, new_max * t->data_size);
> if (new_data == NULL)
> return -1;
>
> - if (t->data) {
> - memcpy(new_data, t->data, t->max_size * t->data_size);
> - SNMP_FREE(t->data);
> - }
> - t->data = (void**)new_data;
> + t->data = new_data;
> t->max_size = new_max;
> }
>
>
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