Changeset 7ebf768

Timestamp:

02/14/18 15:51:27 (3 years ago)

Author:

Shane Alcock <salcock@…>

Branches:

cachetimestamps, develop, etsilive, master, rc-4.0.3, rc-4.0.4, ringdecrementfix, ringperformance

Children:

3004d6c

Parents:

6445c52

Message:

Avoid multiple byteswaps of the same variable in format_dag.

In particular, we can cache the timestamp of the next packet
in a socket buffer rather than re-read it from the buffer every
time we call select_next_packet() -- maybe not such a big issue
when you have two sockets per thread, but very wasteful when you
have 8 sockets per thread.

Keep a local copy of rlen in host byte order when preparing a
packet, so we don't have to repeatedly swap it. Compiler
optimization might make this improvement irrelevant, though?

File:

• lib/format_ndag.c (modified) (8 diffs)

lib/format_ndag.c

@@ -87 +87 @@
         int nextwriteind;
         int savedsize[ENCAP_BUFFERS];
+        uint64_t nextts;
         uint32_t startidle;
         uint64_t recordcount;
@@ -587 +588 @@
         uint16_t ndag_reccount = 0;
         int nr;
+        uint16_t rlen;
 
         if ((flags & TRACE_PREP_OWN_BUFFER) == TRACE_PREP_OWN_BUFFER) {
@@ -629 +631 @@
         if ((ndag_reccount & 0x8000) != 0) {
                 /* Record was truncated -- update rlen appropriately */
-                erfptr->rlen = htons(ssock->savedsize[nr] -
-                                (ssock->nextread - ssock->saved[nr]));
-        }
-        ssock->nextread += ntohs(erfptr->rlen);
+                rlen = ssock->savedsize[nr] -
+                                (ssock->nextread - ssock->saved[nr]);
+                erfptr->rlen = htons(rlen);
+        } else {
+                rlen = ntohs(erfptr->rlen);
+        }
+        ssock->nextread += rlen;
+        ssock->nextts = 0;
 
         assert(ssock->nextread - ssock->saved[nr] <= ssock->savedsize[nr]);
@@ -652 +658 @@
 
         packet->order = erf_get_erf_timestamp(packet);
-        packet->error = packet->payload ? ntohs(erfptr->rlen) :
-                        erf_get_framing_length(packet);
-        return ntohs(erfptr->rlen);
+        packet->error = rlen;
+        return rlen;
 }
 
@@ -734 +739 @@
         ssock->bufwaiting = 0;
         ssock->startidle = 0;
+        ssock->nextts = 0;
 
         for (i = 0; i < ENCAP_BUFFERS; i++) {
@@ -876 +882 @@
 
         assert(ssock->bufavail >= 0);
-
-        if (ssock->nextwriteind >= ENCAP_BUFFERS) {
+        if (ssock->nextwriteind >= ENCAP_BUFFERS) {
                 ssock->nextwriteind = 0;
         }
@@ -1112 +1117 @@
         dag_record_t *daghdr;
 
+        /* If we only have one source, then no need to do any
+         * timestamp parsing or byteswapping.
+         */
+        if (rt->sourcecount == 1) {
+                if (readable_data(&(rt->sources[0]))) {
+                        return &(rt->sources[0]);
+                }
+                return NULL;
+        }       
+
+
         for (i = 0; i < rt->sourcecount; i ++) {
                 if (!readable_data(&(rt->sources[i]))) {
@@ -1117 +1133 @@
                 }
 
-                daghdr = (dag_record_t *)(rt->sources[i].nextread);
-                currentts = bswap_le_to_host64(daghdr->ts);
+                if (rt->sources[i].nextts == 0) {
+                        daghdr = (dag_record_t *)(rt->sources[i].nextread);
+                        currentts = bswap_le_to_host64(daghdr->ts);
+                        rt->sources[i].nextts = currentts;
+                } else {
+                        currentts = rt->sources[i].nextts;
+                }
 
                 if (earliest == 0 || earliest > currentts) {