From: Andrew Rybchenko <arybchenko@solarflare.com>
To: Xiao Wang <xiao.w.wang@intel.com>, <olivier.matz@6wind.com>
Cc: <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] mempool: optimize copy in cache get
Date: Tue, 21 May 2019 12:34:55 +0300 [thread overview]
Message-ID: <98702cfa-66ed-e13f-a5ae-c85eb6d64c2f@solarflare.com> (raw)
In-Reply-To: <20190521090321.138062-1-xiao.w.wang@intel.com>
On 5/21/19 12:03 PM, Xiao Wang wrote:
> Use rte_memcpy to improve the pointer array copy. This optimization method
> has already been applied to __mempool_generic_put() [1], this patch applies
> it to __mempool_generic_get(). Slight performance gain can be observed in
> testpmd txonly test.
>
> [1] 863bfb47449 ("mempool: optimize copy in cache")
>
> Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
> ---
> lib/librte_mempool/rte_mempool.h | 7 +------
> 1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/lib/librte_mempool/rte_mempool.h b/lib/librte_mempool/rte_mempool.h
> index 8053f7a04..975da8d22 100644
> --- a/lib/librte_mempool/rte_mempool.h
> +++ b/lib/librte_mempool/rte_mempool.h
> @@ -1344,15 +1344,11 @@ __mempool_generic_get(struct rte_mempool *mp, void **obj_table,
> unsigned int n, struct rte_mempool_cache *cache)
> {
> int ret;
> - uint32_t index, len;
> - void **cache_objs;
>
> /* No cache provided or cannot be satisfied from cache */
> if (unlikely(cache == NULL || n >= cache->size))
> goto ring_dequeue;
>
> - cache_objs = cache->objs;
> -
> /* Can this be satisfied from the cache? */
> if (cache->len < n) {
> /* No. Backfill the cache first, and then fill from it */
> @@ -1375,8 +1371,7 @@ __mempool_generic_get(struct rte_mempool *mp, void **obj_table,
> }
>
> /* Now fill in the response ... */
> - for (index = 0, len = cache->len - 1; index < n; ++index, len--, obj_table++)
> - *obj_table = cache_objs[len];
> + rte_memcpy(obj_table, &cache->objs[cache->len - n], sizeof(void *) * n);
>
> cache->len -= n;
>
I think the idea of the loop above is to get objects in reverse order to
order
to reuse cache top objects (put last) first. It should improve cache hit
etc.
So, performance effect of the patch could be very different on various CPUs
(with different cache sizes) and various work-loads.
So, I doubt that it is a step in right direction.
Andrew.
next prev parent reply other threads:[~2019-05-21 9:35 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-21 9:03 Xiao Wang
2019-05-21 9:34 ` Andrew Rybchenko [this message]
2019-07-01 13:11 ` Olivier Matz
2019-07-01 14:21 ` Wang, Xiao W
2019-07-01 15:00 ` Olivier Matz
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