> > +CC Beilei as i40e maintainer > > > From: Dharmik Thakkar [mailto:dharmik.thak...@arm.com] > > Sent: Thursday, 13 January 2022 06.37 > > > > Current mempool per core cache implementation stores pointers to mbufs > > On 64b architectures, each pointer consumes 8B This patch replaces it > > with index-based implementation, where in each buffer is addressed by > > (pool base address + index) It reduces the amount of memory/cache > > required for per core cache > > > > L3Fwd performance testing reveals minor improvements in the cache > > performance (L1 and L2 misses reduced by 0.60%) with no change in > > throughput > > > > Suggested-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com> > > Signed-off-by: Dharmik Thakkar <dharmik.thak...@arm.com> > > Reviewed-by: Ruifeng Wang <ruifeng.w...@arm.com> > > --- > > lib/mempool/rte_mempool.h | 150 +++++++++++++++++++++++++- > > lib/mempool/rte_mempool_ops_default.c | 7 ++ > > 2 files changed, 156 insertions(+), 1 deletion(-) > > > > diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h > > index 1e7a3c15273c..f2403fbc97a7 100644 > > --- a/lib/mempool/rte_mempool.h > > +++ b/lib/mempool/rte_mempool.h > > @@ -50,6 +50,10 @@ > > #include <rte_memcpy.h> > > #include <rte_common.h> > > > > +#ifdef RTE_MEMPOOL_INDEX_BASED_LCORE_CACHE > > +#include <rte_vect.h> > > +#endif > > + > > #include "rte_mempool_trace_fp.h" > > > > #ifdef __cplusplus > > @@ -239,6 +243,9 @@ struct rte_mempool { > > int32_t ops_index; > > > > struct rte_mempool_cache *local_cache; /**< Per-lcore local cache */ > > +#ifdef RTE_MEMPOOL_INDEX_BASED_LCORE_CACHE > > + void *pool_base_value; /**< Base value to calculate indices */ > > +#endif > > > > uint32_t populated_size; /**< Number of populated > > objects. */ > > struct rte_mempool_objhdr_list elt_list; /**< List of objects in > > pool */ @@ -1314,7 +1321,22 @@ rte_mempool_cache_flush(struct > > rte_mempool_cache *cache, > > if (cache == NULL || cache->len == 0) > > return; > > rte_mempool_trace_cache_flush(cache, mp); > > + > > +#ifdef RTE_MEMPOOL_INDEX_BASED_LCORE_CACHE > > + unsigned int i; > > + unsigned int cache_len = cache->len; > > + void *obj_table[RTE_MEMPOOL_CACHE_MAX_SIZE * 3]; > > + void *base_value = mp->pool_base_value; > > + uint32_t *cache_objs = (uint32_t *) cache->objs; > > Hi Dharmik and Honnappa, > > The essence of this patch is based on recasting the type of the objs field in > the > rte_mempool_cache structure from an array of pointers to an array of > uint32_t. > > However, this effectively breaks the ABI, because the rte_mempool_cache > structure is public and part of the API. The patch does not change the public structure, the new member is under compile time flag, not sure how it breaks the ABI.
> > Some drivers [1] even bypass the mempool API and access the > rte_mempool_cache structure directly, assuming that the objs array in the > cache is an array of pointers. So you cannot recast the fields in the > rte_mempool_cache structure the way this patch requires. IMO, those drivers are at fault. The mempool cache structure is public only because the APIs are inline. We should still maintain modularity and not use the members of structures belonging to another library directly. A similar effort involving rte_ring was not accepted sometime back [1] [1] http://inbox.dpdk.org/dev/dbapr08mb5814907968595ee56f5e20a798...@dbapr08mb5814.eurprd08.prod.outlook.com/ > > Although I do consider bypassing an API's accessor functions "spaghetti > code", this driver's behavior is formally acceptable as long as the > rte_mempool_cache structure is not marked as internal. > > I really liked your idea of using indexes instead of pointers, so I'm very > sorry to > shoot it down. :-( > > [1]: E.g. the Intel i40e PMD, > http://code.dpdk.org/dpdk/latest/source/drivers/net/i40e/i40e_rxtx_vec_avx > 512.c#L25 It is possible to throw an error when this feature is enabled in this file. Alternatively, this PMD could implement the code for index based mempool. > > -Morten
