[dpdk-dev] [PATCH] Fix for LRU corrupted returns
Neil Horman
nhorman at tuxdriver.com
Thu Sep 25 12:21:55 CEST 2014
On Thu, Sep 25, 2014 at 07:46:16AM +0000, Saha, Avik (AWS) wrote:
> This is a patch to a problem that I have faced (described in the thread) and this works for me.
>
> 1) Since the data_size_shl was getting its value from the key_size, the table data entries were being corrupted when the calculation to shift the number of bits was being made based on the key_size (according to the document the key_size and entry_size are independently configurable) - With this fix, we get the MSB that is set in entry_size (also removes the constraint of this having to be a power of 2 - not entirely sure if this was the reason the constraint was kept though)
> 2) The document does not say that the entry_size needs to be a power of 2 and this was failing silently when I was trying to bring my application up.
>
> diff --git a/DPDK/lib/librte_table/rte_table_hash_lru.c b/DPDK/lib/librte_table/rte_table_hash_lru.c
> index d1a4984..4ec9aa4 100644
> --- a/DPDK/lib/librte_table/rte_table_hash_lru.c
> +++ b/DPDK/lib/librte_table/rte_table_hash_lru.c
> @@ -153,8 +153,10 @@ rte_table_hash_lru_create(void *params, int socket_id, uint32_t entry_size)
> uint32_t i;
>
> /* Check input parameters */
> - if ((check_params_create(p) != 0) ||
> - (!rte_is_power_of_2(entry_size)) ||
> + // Commenting out the power of 2 check on the entry_size since the
> + // Programmers Guide does not call this out and we are going to handle
> + // the data_size_shl of the table later on (Line 197)
Please remove the reference to Line 197 here. Thats not going to remain
accurate for very long.
> + if ((check_params_create(p) != 0) ||
> ((sizeof(struct rte_table_hash) % CACHE_LINE_SIZE) != 0) ||
> (sizeof(struct bucket) != (CACHE_LINE_SIZE / 2))) {
> return NULL;
> @@ -192,7 +194,7 @@ rte_table_hash_lru_create(void *params, int socket_id, uint32_t entry_size)
> /* Internal */
> t->bucket_mask = t->n_buckets - 1;
> t->key_size_shl = __builtin_ctzl(p->key_size);
> - t->data_size_shl = __builtin_ctzl(p->key_size);
> + t->data_size_shl = 32 - (__builtin_clz(entry_size));
I presume the 32 value here is a cache line size? That should be replaced with
CACHE_LINE_SIZE...Though looking at it, that doesn't seem sufficient. Seems
like we need a eal abstraction to dynamically tell us what the cache line size
is (we can read it from /proc/cpuinfo in linux, not sure about bsd).
Neil
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