Re: [dpdk-dev] [PATCH] mempool: limit cache_size

[Bruce Richardson <bruce.richardson@intel.com>]

On Mon, May 18, 2015 at 01:27:45PM +0100, Zoltan Kiss wrote:
> Hi,
> 
> Any opinion on this patch?
> 
> Regards,
> 
> Zoltan
> 
> On 13/05/15 19:59, Zoltan Kiss wrote:
> >Otherwise cache_flushthresh can be bigger than n, and
> >a consumer can starve others by keeping every element
> >either in use or in the cache.
> >
> >Signed-off-by: Zoltan Kiss <zoltan.kiss@linaro.org>

Seems reasonable enough to me.

Acked-by: Bruce Richardson <bruce.richardson@intel.com>

> >---
> >  lib/librte_mempool/rte_mempool.c | 3 ++-
> >  lib/librte_mempool/rte_mempool.h | 2 +-
> >  2 files changed, 3 insertions(+), 2 deletions(-)
> >
> >diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
> >index cf7ed76..ca6cd9c 100644
> >--- a/lib/librte_mempool/rte_mempool.c
> >+++ b/lib/librte_mempool/rte_mempool.c
> >@@ -440,7 +440,8 @@ rte_mempool_xmem_create(const char *name, unsigned n, unsigned elt_size,
> >  	mempool_list = RTE_TAILQ_CAST(rte_mempool_tailq.head, rte_mempool_list);
> >
> >  	/* asked cache too big */
> >-	if (cache_size > RTE_MEMPOOL_CACHE_MAX_SIZE) {
> >+	if (cache_size > RTE_MEMPOOL_CACHE_MAX_SIZE ||
> >+	    (uint32_t) cache_size * CACHE_FLUSHTHRESH_MULTIPLIER > n) {
> >  		rte_errno = EINVAL;
> >  		return NULL;
> >  	}
> >diff --git a/lib/librte_mempool/rte_mempool.h b/lib/librte_mempool/rte_mempool.h
> >index 9001312..a4a9610 100644
> >--- a/lib/librte_mempool/rte_mempool.h
> >+++ b/lib/librte_mempool/rte_mempool.h
> >@@ -468,7 +468,7 @@ typedef void (rte_mempool_ctor_t)(struct rte_mempool *, void *);
> >   *   If cache_size is non-zero, the rte_mempool library will try to
> >   *   limit the accesses to the common lockless pool, by maintaining a
> >   *   per-lcore object cache. This argument must be lower or equal to
> >- *   CONFIG_RTE_MEMPOOL_CACHE_MAX_SIZE. It is advised to choose
> >+ *   CONFIG_RTE_MEMPOOL_CACHE_MAX_SIZE and n / 1.5. It is advised to choose
> >   *   cache_size to have "n modulo cache_size == 0": if this is
> >   *   not the case, some elements will always stay in the pool and will
> >   *   never be used. The access to the per-lcore table is of course
> >