examples/l3fwd: improve grouping by destination port
authorKonstantin Ananyev <konstantin.ananyev@intel.com>
Tue, 22 Jul 2014 16:04:47 +0000 (17:04 +0100)
committerThomas Monjalon <thomas.monjalon@6wind.com>
Fri, 1 Aug 2014 16:25:05 +0000 (18:25 +0200)
Latest changes introduced a small degradation for the corner case
when each input packet is destined to the different port.
For the test-case when 1 core manages 4 ports and packet stream looks like:
IPV4_DSTPORT0, IPV4_DSTPORT1, IPV4_DSTPORT3, IPV4_DSTPORT4, IPV4_DSTPORT0, ...
non-optimised code path outperforms optimised one by 2-3%.
These changes supposed to close that gap.
From my testing: now for the case described above optimised code path
produces same numbers as non-optimised one.
For other test-cases numbers remain about the same.

Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
examples/l3fwd/main.c

index 73a039e..bef409a 100755 (executable)
@@ -1271,6 +1271,168 @@ processx4_step3(struct rte_mbuf *pkt[FWDSTEP], uint16_t dst_port[FWDSTEP])
                &dst_port[3], pkt[3]->ol_flags);
 }
 
+/*
+ * We group consecutive packets with the same destionation port into one burst.
+ * To avoid extra latency this is done together with some other packet
+ * processing, but after we made a final decision about packet's destination.
+ * To do this we maintain:
+ * pnum - array of number of consecutive packets with the same dest port for
+ * each packet in the input burst.
+ * lp - pointer to the last updated element in the pnum.
+ * dlp - dest port value lp corresponds to.
+ */
+
+#define        GRPSZ   (1 << FWDSTEP)
+#define        GRPMSK  (GRPSZ - 1)
+
+#define GROUP_PORT_STEP(dlp, dcp, lp, pn, idx) do { \
+       if (likely((dlp) == (dcp)[(idx)])) {         \
+               (lp)[0]++;                           \
+       } else {                                     \
+               (dlp) = (dcp)[idx];                  \
+               (lp) = (pn) + (idx);                 \
+               (lp)[0] = 1;                         \
+       }                                            \
+} while (0)
+
+/*
+ * Group consecutive packets with the same destination port in bursts of 4.
+ * Suppose we have array of destionation ports:
+ * dst_port[] = {a, b, c, d,, e, ... }
+ * dp1 should contain: <a, b, c, d>, dp2: <b, c, d, e>.
+ * We doing 4 comparisions at once and the result is 4 bit mask.
+ * This mask is used as an index into prebuild array of pnum values.
+ */
+static inline uint16_t *
+port_groupx4(uint16_t pn[FWDSTEP + 1], uint16_t *lp, __m128i dp1, __m128i dp2)
+{
+       static const struct {
+               uint64_t pnum; /* prebuild 4 values for pnum[]. */
+               int32_t  idx;  /* index for new last updated elemnet. */
+               uint16_t lpv;  /* add value to the last updated element. */
+       } gptbl[GRPSZ] = {
+       {
+               /* 0: a != b, b != c, c != d, d != e */
+               .pnum = UINT64_C(0x0001000100010001),
+               .idx = 4,
+               .lpv = 0,
+       },
+       {
+               /* 1: a == b, b != c, c != d, d != e */
+               .pnum = UINT64_C(0x0001000100010002),
+               .idx = 4,
+               .lpv = 1,
+       },
+       {
+               /* 2: a != b, b == c, c != d, d != e */
+               .pnum = UINT64_C(0x0001000100020001),
+               .idx = 4,
+               .lpv = 0,
+       },
+       {
+               /* 3: a == b, b == c, c != d, d != e */
+               .pnum = UINT64_C(0x0001000100020003),
+               .idx = 4,
+               .lpv = 2,
+       },
+       {
+               /* 4: a != b, b != c, c == d, d != e */
+               .pnum = UINT64_C(0x0001000200010001),
+               .idx = 4,
+               .lpv = 0,
+       },
+       {
+               /* 5: a == b, b != c, c == d, d != e */
+               .pnum = UINT64_C(0x0001000200010002),
+               .idx = 4,
+               .lpv = 1,
+       },
+       {
+               /* 6: a != b, b == c, c == d, d != e */
+               .pnum = UINT64_C(0x0001000200030001),
+               .idx = 4,
+               .lpv = 0,
+       },
+       {
+               /* 7: a == b, b == c, c == d, d != e */
+               .pnum = UINT64_C(0x0001000200030004),
+               .idx = 4,
+               .lpv = 3,
+       },
+       {
+               /* 8: a != b, b != c, c != d, d == e */
+               .pnum = UINT64_C(0x0002000100010001),
+               .idx = 3,
+               .lpv = 0,
+       },
+       {
+               /* 9: a == b, b != c, c != d, d == e */
+               .pnum = UINT64_C(0x0002000100010002),
+               .idx = 3,
+               .lpv = 1,
+       },
+       {
+               /* 0xa: a != b, b == c, c != d, d == e */
+               .pnum = UINT64_C(0x0002000100020001),
+               .idx = 3,
+               .lpv = 0,
+       },
+       {
+               /* 0xb: a == b, b == c, c != d, d == e */
+               .pnum = UINT64_C(0x0002000100020003),
+               .idx = 3,
+               .lpv = 2,
+       },
+       {
+               /* 0xc: a != b, b != c, c == d, d == e */
+               .pnum = UINT64_C(0x0002000300010001),
+               .idx = 2,
+               .lpv = 0,
+       },
+       {
+               /* 0xd: a == b, b != c, c == d, d == e */
+               .pnum = UINT64_C(0x0002000300010002),
+               .idx = 2,
+               .lpv = 1,
+       },
+       {
+               /* 0xe: a != b, b == c, c == d, d == e */
+               .pnum = UINT64_C(0x0002000300040001),
+               .idx = 1,
+               .lpv = 0,
+       },
+       {
+               /* 0xf: a == b, b == c, c == d, d == e */
+               .pnum = UINT64_C(0x0002000300040005),
+               .idx = 0,
+               .lpv = 4,
+       },
+       };
+
+       union {
+               uint16_t u16[FWDSTEP + 1];
+               uint64_t u64;
+       } *pnum = (void *)pn;
+
+       int32_t v;
+
+       dp1 = _mm_cmpeq_epi16(dp1, dp2);
+       dp1 = _mm_unpacklo_epi16(dp1, dp1);
+       v = _mm_movemask_ps((__m128)dp1);
+
+       /* update last port counter. */
+       lp[0] += gptbl[v].lpv;
+
+       /* if dest port value has changed. */
+       if (v != GRPMSK) {
+               lp = pnum->u16 + gptbl[v].idx;
+               lp[0] = 1;
+               pnum->u64 = gptbl[v].pnum;
+       }
+
+       return lp;
+}
+
 #endif /* APP_LOOKUP_METHOD */
 
 /* main processing loop */
@@ -1289,9 +1451,12 @@ main_loop(__attribute__((unused)) void *dummy)
 #if ((APP_LOOKUP_METHOD == APP_LOOKUP_LPM) && \
        (ENABLE_MULTI_BUFFER_OPTIMIZE == 1))
        int32_t k;
+       uint16_t dlp;
+       uint16_t *lp;
        uint16_t dst_port[MAX_PKT_BURST];
        __m128i dip[MAX_PKT_BURST / FWDSTEP];
        uint32_t flag[MAX_PKT_BURST / FWDSTEP];
+       uint16_t pnum[MAX_PKT_BURST + 1];
 #endif
 
        prev_tsc = 0;
@@ -1402,9 +1567,61 @@ main_loop(__attribute__((unused)) void *dummy)
                                        &pkts_burst[j], &dst_port[j]);
                        }
 
+                       /*
+                        * Finish packet processing and group consecutive
+                        * packets with the same destination port.
+                        */
                        k = RTE_ALIGN_FLOOR(nb_rx, FWDSTEP);
-                       for (j = 0; j != k; j += FWDSTEP) {
-                               processx4_step3(&pkts_burst[j], &dst_port[j]);
+                       if (k != 0) {
+                               __m128i dp1, dp2;
+
+                               lp = pnum;
+                               lp[0] = 1;
+
+                               processx4_step3(pkts_burst, dst_port);
+
+                               /* dp1: <d[0], d[1], d[2], d[3], ... > */
+                               dp1 = _mm_loadu_si128((__m128i *)dst_port);
+
+                               for (j = FWDSTEP; j != k; j += FWDSTEP) {
+                                       processx4_step3(&pkts_burst[j],
+                                               &dst_port[j]);
+
+                                       /*
+                                        * dp2:
+                                        * <d[j-3], d[j-2], d[j-1], d[j], ... >
+                                        */
+                                       dp2 = _mm_loadu_si128((__m128i *)
+                                               &dst_port[j - FWDSTEP + 1]);
+                                       lp  = port_groupx4(&pnum[j - FWDSTEP],
+                                               lp, dp1, dp2);
+
+                                       /*
+                                        * dp1:
+                                        * <d[j], d[j+1], d[j+2], d[j+3], ... >
+                                        */
+                                       dp1 = _mm_srli_si128(dp2,
+                                               (FWDSTEP - 1) *
+                                               sizeof(dst_port[0]));
+                               }
+
+                               /*
+                                * dp2: <d[j-3], d[j-2], d[j-1], d[j-1], ... >
+                                */
+                               dp2 = _mm_shufflelo_epi16(dp1, 0xf9);
+                               lp  = port_groupx4(&pnum[j - FWDSTEP], lp,
+                                       dp1, dp2);
+
+                               /*
+                                * remove values added by the last repeated
+                                * dst port.
+                                */
+                               lp[0]--;
+                               dlp = dst_port[j - 1];
+                       } else {
+                               /* set dlp and lp to the never used values. */
+                               dlp = BAD_PORT - 1;
+                               lp = pnum + MAX_PKT_BURST;
                        }
 
                        /* Process up to last 3 packets one by one. */
@@ -1412,39 +1629,41 @@ main_loop(__attribute__((unused)) void *dummy)
                        case 3:
                                process_packet(qconf, pkts_burst[j],
                                        dst_port + j, portid);
+                               GROUP_PORT_STEP(dlp, dst_port, lp, pnum, j);
                                j++;
                        case 2:
                                process_packet(qconf, pkts_burst[j],
                                        dst_port + j, portid);
+                               GROUP_PORT_STEP(dlp, dst_port, lp, pnum, j);
                                j++;
                        case 1:
                                process_packet(qconf, pkts_burst[j],
                                        dst_port + j, portid);
+                               GROUP_PORT_STEP(dlp, dst_port, lp, pnum, j);
                                j++;
                        }
 
                        /*
                         * Send packets out, through destination port.
-                        * Try to group packets with the same destination port.
+                        * Consecuteve pacekts with the same destination port
+                        * are already grouped together.
                         * If destination port for the packet equals BAD_PORT,
                         * then free the packet without sending it out.
                         */
-                       for (j = 0; j < nb_rx; j = k) {
-
-                               uint16_t cn, pn = dst_port[j];
+                       for (j = 0; j < nb_rx; j += k) {
 
-                               k = j;
-                               do {
-                                       cn = dst_port[k];
-                               } while (cn != BAD_PORT && pn == cn &&
-                                               ++k < nb_rx);
+                               int32_t m;
+                               uint16_t pn;
 
-                               send_packetsx4(qconf, pn, pkts_burst + j,
-                                       k - j);
+                               pn = dst_port[j];
+                               k = pnum[j];
 
-                               if (cn == BAD_PORT) {
-                                       rte_pktmbuf_free(pkts_burst[k]);
-                                       k += 1;
+                               if (likely(pn != BAD_PORT)) {
+                                       send_packetsx4(qconf, pn,
+                                               pkts_burst + j, k);
+                               } else {
+                                       for (m = j; m != j + k; m++)
+                                               rte_pktmbuf_free(pkts_burst[m]);
                                }
                        }