Re: [PATCH] mbuf: cleanup rte_pktmbuf_lastseg(), fix atomic usage
From: Ananyev, Konstantin <hidden>
Date: 2017-11-15 11:08:21
Hi Hanon,
quoted hunk
-----Original Message----- From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Hanoh Haim Sent: Wednesday, November 15, 2017 8:36 AM To: dev@dpdk.org Cc: Hanoh Haim <redacted> Subject: [dpdk-dev] [PATCH] mbuf: cleanup rte_pktmbuf_lastseg(), fix atomic usage Signed-off-by: Hanoh Haim <redacted> --- lib/librte_mbuf/rte_mbuf.h | 27 +++++++++++++-------------- 1 file changed, 13 insertions(+), 14 deletions(-)diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h index 7e326bb..ab110f8 100644 --- a/lib/librte_mbuf/rte_mbuf.h +++ b/lib/librte_mbuf/rte_mbuf.h@@ -1159,6 +1159,15 @@ static inline void rte_pktmbuf_reset(struct rte_mbuf *m)__rte_mbuf_sanity_check(m, 1); } + +static __rte_always_inline void rte_pktmbuf_reset_before_free(struct rte_mbuf *m) +{ + if (m->next != NULL) { + m->next = NULL; + m->nb_segs = 1; + } +} + /** * Allocate a new mbuf from a mempool. *@@ -1323,8 +1332,7 @@ static inline void rte_pktmbuf_detach(struct rte_mbuf *m)m->ol_flags = 0; if (rte_mbuf_refcnt_update(md, -1) == 0) { - md->next = NULL; - md->nb_segs = 1; + rte_pktmbuf_reset_before_free(md); rte_mbuf_refcnt_set(md, 1); rte_mbuf_raw_free(md); }@@ -1354,25 +1362,16 @@ rte_pktmbuf_prefree_seg(struct rte_mbuf *m)if (RTE_MBUF_INDIRECT(m)) rte_pktmbuf_detach(m); - if (m->next != NULL) { - m->next = NULL; - m->nb_segs = 1; - } - + rte_pktmbuf_reset_before_free(m); return m; - } else if (rte_atomic16_add_return(&m->refcnt_atomic, -1) == 0) { - + } else if (rte_mbuf_refcnt_update(m, -1) == 0) {
That would cause extra read; cmp (and possible slowdown) for atomic refcnt. If that really need to be fixed - probably we need to introduce a new function that would do update without trying to read refctn first - rte_mbuf_refcnt_update_blind() or so. Konstantin
if (RTE_MBUF_INDIRECT(m))
rte_pktmbuf_detach(m);
- if (m->next != NULL) {
- m->next = NULL;
- m->nb_segs = 1;
- }
+ rte_pktmbuf_reset_before_free(m);
rte_mbuf_refcnt_set(m, 1);
-
return m;
}
return NULL;
--
2.9.3