Re: [PATCH 1/2] mbuf: fix performance/cache resource issue with 128-byte cache line targets

-----Original Message-----
From: Jerin Jacob [mailto:jerin.jacob@caviumnetworks.com]
Sent: Sunday, December 06, 2015 3:59 PM
To: dev@dpdk.org
Cc: thomas.monjalon@6wind.com; Richardson, Bruce; olivier.matz@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 <redacted>
---
 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