On 18/05/15 14:14, Ananyev, Konstantin wrote: > > >> -----Original Message----- >> From: Zoltan Kiss [mailto:zoltan.kiss at linaro.org] >> Sent: Monday, May 18, 2015 1:50 PM >> To: Ananyev, Konstantin; dev at dpdk.org >> Subject: Re: [dpdk-dev] [PATCH] mempool: limit cache_size >> >> >> >> On 18/05/15 13:41, Ananyev, Konstantin wrote: >>> >>> >>>> -----Original Message----- >>>> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Zoltan Kiss >>>> Sent: Monday, May 18, 2015 1:28 PM >>>> To: dev at dpdk.org >>>> Subject: Re: [dpdk-dev] [PATCH] mempool: limit cache_size >>>> >>>> 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 at linaro.org> >>>>> --- >>>>> 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; >>>>> } >>> >>> Why just no 'cache_size > n' then? >> >> The commit message says: "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." > > Ah yes, you right - your condition is more restrictive, which is better. > Though here you implicitly convert cache_size and n to floats and compare 2 > floats : > (uint32_t) cache_size * CACHE_FLUSHTHRESH_MULTIPLIER > n) > Shouldn't it be: > (uint32_t)(cache_size * CACHE_FLUSHTHRESH_MULTIPLIER) > n) > So we do conversion back to uint32_t compare to unsigned integers instead? > Same as below: > mp->cache_flushthresh = (uint32_t) > (cache_size * CACHE_FLUSHTHRESH_MULTIPLIER);
To bring it further: how about ditching the whole cache_flushthresh member of the mempool structure, and use this: #define CACHE_FLUSHTHRESH(mp) (uint32_t)((mp)->cache_size * 1.5) Furthermore, do we want to expose the flush threshold multiplier through the config file? > ? > > In fact, as we use it more than once, it probably makes sense to create a > macro for it, > something like: > #define CALC_CACHE_FLUSHTHRESH(c) ((uint32_t)((c) * > CACHE_FLUSHTHRESH_MULTIPLIER) > > Or even > > #define CALC_CACHE_FLUSHTHRESH(c) ((typeof (c))((c) * > CACHE_FLUSHTHRESH_MULTIPLIER) > > > Konstantin > >> >>> Konstantin >>> >>>>> 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 >>>>>
