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From: Bruce Richardson <bruce.richardson@intel.com>
To: dev@dpdk.org
Subject: [dpdk-dev] [PATCH] distributor: add comments to make code more readable
Date: Thu,  6 Nov 2014 13:55:32 +0000	[thread overview]
Message-ID: <1415282132-11056-1-git-send-email-bruce.richardson@intel.com> (raw)
In-Reply-To: <9190772.1rnKUO3oNV@xps13>

From: "Bruce Richardson" <bruce.richardson@intel.com>

Add in some additional comments around more complex areas of the code
so as to make the code easier to read and understand.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
 lib/librte_distributor/rte_distributor.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/lib/librte_distributor/rte_distributor.c b/lib/librte_distributor/rte_distributor.c
index 585ff88..656ee5c 100644
--- a/lib/librte_distributor/rte_distributor.c
+++ b/lib/librte_distributor/rte_distributor.c
@@ -92,6 +92,7 @@ struct rte_distributor {
 	unsigned num_workers;                 /**< Number of workers polling */
 
 	uint32_t in_flight_tags[RTE_MAX_LCORE];
+		/**< Tracks the tag being processed per core, 0 == no pkt */
 	struct rte_distributor_backlog backlog[RTE_MAX_LCORE];
 
 	union rte_distributor_buffer bufs[RTE_MAX_LCORE];
@@ -282,10 +283,22 @@ rte_distributor_process(struct rte_distributor *d,
 			next_mb = mbufs[next_idx++];
 			next_value = (((int64_t)(uintptr_t)next_mb)
 					<< RTE_DISTRIB_FLAG_BITS);
+			/*
+			 * Set the low bit on the tag, so we can guarantee that
+			 * we never store a tag value of zero. That means we can
+			 * use the zero-value to indicate that no packet is
+			 * being processed by a worker.
+			 */
 			new_tag = (next_mb->hash.rss | 1);
 
 			uint32_t match = 0;
 			unsigned i;
+			/*
+			 * to scan for a match use "xor" and "not" to get a 0/1
+			 * value, then use shifting to merge to single "match"
+			 * variable, where a one-bit indicates a match for the
+			 * worker given by the bit-position
+			 */
 			for (i = 0; i < d->num_workers; i++)
 				match |= (!(d->in_flight_tags[i] ^ new_tag)
 					<< i);
-- 
2.1.1

  parent reply	other threads:[~2014-11-06 13:46 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-05 13:30 [dpdk-dev] [PATCH] Add user defined tag calculation callback to librte_distributor Qinglai Xiao
2014-11-05 14:27 ` Bruce Richardson
2014-11-05 15:11   ` jigsaw
2014-11-05 16:36     ` Bruce Richardson
2014-11-05 17:24       ` jigsaw
2014-11-06  9:22         ` Bruce Richardson
2014-11-06 10:14           ` jigsaw
2014-11-06 10:36           ` Thomas Monjalon
2014-11-06 12:36             ` [dpdk-dev] 答复: [PATCH] Add user defined tag calculation callback tolibrte_distributor Qinglai Xiao
2014-11-06 13:59               ` Bruce Richardson
2014-11-06 18:01                 ` jigsaw
2014-11-06 19:52                   ` jigsaw
2014-11-07  9:45                     ` Bruce Richardson
2014-11-07 12:38                       ` jigsaw
2014-11-07 13:53                         ` Bruce Richardson
2014-11-07 14:31                           ` jigsaw
     [not found]                             ` <20141107144410.GC12092@bricha3-MOBL3>
2014-11-07 14:52                               ` jigsaw
2014-11-07 15:04                                 ` Bruce Richardson
2014-11-07 15:18                                   ` jigsaw
2014-11-06 13:55             ` Bruce Richardson [this message]
2014-11-07 14:08               ` [dpdk-dev] [PATCH] distributor: add comments to make code more readable Thomas Monjalon
2014-11-07 14:31                 ` jigsaw
2014-11-06 13:57             ` [dpdk-dev] [PATCH] Add user defined tag calculation callback to librte_distributor Bruce Richardson
2014-11-05 15:13   ` Ananyev, Konstantin
2014-11-05 15:24     ` jigsaw

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