[dpdk-dev] [PATCH 1/2] mbuf: fix performance/cache resource issue with 128-byte cache line targets
Ananyev, Konstantin
konstantin.ananyev at intel.com
Mon Dec 7 16:21:33 CET 2015
Hi Jerin,
> -----Original Message-----
> From: Jerin Jacob [mailto:jerin.jacob at caviumnetworks.com]
> Sent: Sunday, December 06, 2015 3:59 PM
> To: dev at dpdk.org
> Cc: thomas.monjalon at 6wind.com; Richardson, Bruce; olivier.matz at 6wind.com; Dumitrescu, Cristian; Ananyev, Konstantin; Jerin
> Jacob
> Subject: [dpdk-dev] [PATCH 1/2] mbuf: fix performance/cache resource issue with 128-byte cache line targets
>
> No need to split mbuf structure to two cache lines for 128-byte cache line
> size targets as it can fit on a single 128-byte cache line.
>
> Signed-off-by: Jerin Jacob <jerin.jacob at caviumnetworks.com>
> ---
> app/test/test_mbuf.c | 4 ++++
> lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h | 4 ++++
> lib/librte_mbuf/rte_mbuf.h | 2 ++
> 3 files changed, 10 insertions(+)
>
> diff --git a/app/test/test_mbuf.c b/app/test/test_mbuf.c
> index b32bef6..5e21075 100644
> --- a/app/test/test_mbuf.c
> +++ b/app/test/test_mbuf.c
> @@ -930,7 +930,11 @@ test_failing_mbuf_sanity_check(void)
> static int
> test_mbuf(void)
> {
> +#if RTE_CACHE_LINE_SIZE == 64
> RTE_BUILD_BUG_ON(sizeof(struct rte_mbuf) != RTE_CACHE_LINE_SIZE * 2);
> +#elif RTE_CACHE_LINE_SIZE == 128
> + RTE_BUILD_BUG_ON(sizeof(struct rte_mbuf) != RTE_CACHE_LINE_SIZE);
> +#endif
>
> /* create pktmbuf pool if it does not exist */
> if (pktmbuf_pool == NULL) {
> diff --git a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h b/lib/librte_eal/linuxapp/eal/include/exec-
> env/rte_kni_common.h
> index bd1cc09..e724af7 100644
> --- a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
> +++ b/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
> @@ -121,8 +121,12 @@ struct rte_kni_mbuf {
> uint32_t pkt_len; /**< Total pkt len: sum of all segment data_len. */
> uint16_t data_len; /**< Amount of data in segment buffer. */
>
> +#if RTE_CACHE_LINE_SIZE == 64
> /* fields on second cache line */
> char pad3[8] __attribute__((__aligned__(RTE_CACHE_LINE_SIZE)));
> +#elif RTE_CACHE_LINE_SIZE == 128
> + char pad3[24];
> +#endif
> void *pool;
> void *next;
> };
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index f234ac9..0bf55e0 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -813,8 +813,10 @@ struct rte_mbuf {
>
> uint16_t vlan_tci_outer; /**< Outer VLAN Tag Control Identifier (CPU order) */
>
> +#if RTE_CACHE_LINE_SIZE == 64
> /* second cache line - fields only used in slow path or on TX */
> MARKER cacheline1 __rte_cache_aligned;
> +#endif
I suppose you'll need to keep same space reserved for first 64B even on systems with 128B cache-line.
Otherwise we can endup with different mbuf format for systems with 128B cache-line.
Another thing - now we have __rte_cache_aligned all over the places, and I don't know is to double
sizes of all these structures is a good idea.
Again, #if RTE_CACHE_LINE_SIZE == 64 ... all over the places looks a bit clumsy.
Wonder can we have __rte_cache_aligned/ RTE_CACHE_LINE_SIZE architecture specific,
but introduce RTE_CACHE_MIN_LINE_SIZE(==64)/ __rte_cache_min_aligned and used it for mbuf
(and might be other places).
Konstantin
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