[Qemu-devel] [PATCH 1/2] colo: compare the packet based on the tcp sequence number

[Mao Zhongyi]

    The primary and secondary guest has the same TCP stream, but the
    the packet sizes are different due to the different fragmentation.

    In the current impletation, compare the packet with the size of
    payload, but packets of the same size and payload are very few,
    so it triggers checkopint frequently, which leads to a very low
    performance of the tcp packet comparison. In addtion, the method
    of comparing the size of packet is not correct in itself.

    like that:
    We send this payload:
    ------------------------------
    | header |1|2|3|4|5|6|7|8|9|0|
    ------------------------------

    primary:
    ppkt1:
    ----------------
    | header |1|2|3|
    ----------------
    ppkt2:
    ------------------------
    | header |4|5|6|7|8|9|0|
    ------------------------

    secondary:
    spkt1:
    ------------------------------
    | header |1|2|3|4|5|6|7|8|9|0|
    ------------------------------

    In the original method, ppkt1 and ppkt2 are diffrent in size and
    spkt1, so they can't compare and trigger the checkpoint.

    I have tested FTP get 200M and 1G file many times, I found that
    the performance was less than 1% of the native.

    Now I reconstructed the comparison of TCP packets based on the
    TCP sequence number. first of all, ppkt1 and spkt1 have the same
    starting sequence number, so they can compare, even though their
    length is different. And then ppkt1 with a smaller payload length
    is used as the comparison length, if the payload is same, send
    out the ppkt1 and record the offset(the length of ppkt1 payload)
    in spkt1. The next comparison, ppkt2 and spkt1 can be compared
    from the recorded position of spkt1.

    like that:
    ----------------
    | header |1|2|3| ppkt1
    ---------|-----|
             |     |
    ---------v-----v--------------
    | header |1|2|3|4|5|6|7|8|9|0| spkt1
    ---------------|\------------|
                   | \offset     |
          ---------v-------------v
          | header |4|5|6|7|8|9|0| ppkt2
          ------------------------

    In this way, the performance can reach native 20% in my multiple
    tests.

Cc: Zhang Chen <address@hidden>
Cc: Li Zhijian <address@hidden>
Cc: Jason Wang <address@hidden>

Reported-by: Zhang Chen <address@hidden>
Signed-off-by: Mao Zhongyi <address@hidden>
Signed-off-by: Li Zhijian <address@hidden>
---
 net/colo-compare.c | 300 +++++++++++++++++++++++++++++++++--------------------
 net/colo.c         |   8 ++
 net/colo.h         |  14 +++
 3 files changed, 211 insertions(+), 111 deletions(-)

diff --git a/net/colo-compare.c b/net/colo-compare.c
index 1ce195f..0752e9f 100644
--- a/net/colo-compare.c
+++ b/net/colo-compare.c
@@ -38,6 +38,9 @@
 #define COMPARE_READ_LEN_MAX NET_BUFSIZE
 #define MAX_QUEUE_SIZE 1024
 
+#define COLO_COMPARE_FREE_PRIMARY     0x01
+#define COLO_COMPARE_FREE_SECONDARY   0x02
+
 /* TODO: Should be configurable */
 #define REGULAR_PACKET_CHECK_MS 3000
 
@@ -112,14 +115,31 @@ static gint seq_sorter(Packet *a, Packet *b, gpointer 
data)
     return ntohl(atcp->th_seq) - ntohl(btcp->th_seq);
 }
 
+static void fill_pkt_seq(void *data, uint32_t *max_ack)
+{
+    Packet *pkt = data;
+    struct tcphdr *tcphd;
+
+    tcphd = (struct tcphdr *)pkt->transport_header;
+
+    pkt->tcp_seq = ntohl(tcphd->th_seq);
+    pkt->tcp_ack = ntohl(tcphd->th_ack);
+    *max_ack = *max_ack > pkt->tcp_ack ? *max_ack : pkt->tcp_ack;
+    pkt->hdsize = pkt->transport_header - (uint8_t *)pkt->data
+                  + (tcphd->th_off << 2) - pkt->vnet_hdr_len;
+    pkt->pdsize = pkt->size - pkt->hdsize;
+    pkt->seq_end = pkt->tcp_seq + pkt->pdsize;
+}
+
 /*
  * Return 1 on success, if return 0 means the
  * packet will be dropped
  */
-static int colo_insert_packet(GQueue *queue, Packet *pkt)
+static int colo_insert_packet(GQueue *queue, Packet *pkt, uint32_t *max_ack)
 {
     if (g_queue_get_length(queue) <= MAX_QUEUE_SIZE) {
         if (pkt->ip->ip_p == IPPROTO_TCP) {
+            fill_pkt_seq(pkt, max_ack);
             g_queue_insert_sorted(queue,
                                   pkt,
                                   (GCompareDataFunc)seq_sorter,
@@ -169,12 +189,12 @@ static int packet_enqueue(CompareState *s, int mode, 
Connection **con)
     }
 
     if (mode == PRIMARY_IN) {
-        if (!colo_insert_packet(&conn->primary_list, pkt)) {
+        if (!colo_insert_packet(&conn->primary_list, pkt, &conn->pack)) {
             error_report("colo compare primary queue size too big,"
                          "drop packet");
         }
     } else {
-        if (!colo_insert_packet(&conn->secondary_list, pkt)) {
+        if (!colo_insert_packet(&conn->secondary_list, pkt, &conn->sack)) {
             error_report("colo compare secondary queue size too big,"
                          "drop packet");
         }
@@ -184,6 +204,167 @@ static int packet_enqueue(CompareState *s, int mode, 
Connection **con)
     return 0;
 }
 
+static inline bool after(uint32_t seq1, uint32_t seq2)
+{
+        return (int32_t)(seq1 - seq2) > 0;
+}
+
+static void colo_release_primary_pkt(CompareState *s, Packet *pkt)
+{
+    int ret;
+    ret = compare_chr_send(s,
+                           pkt->data,
+                           pkt->size,
+                           pkt->vnet_hdr_len);
+    if (ret < 0) {
+        error_report("colo send primary packet failed");
+    }
+    trace_colo_compare_main("packet same and release packet");
+    packet_destroy(pkt, NULL);
+}
+
+static bool colo_compare_payload(Packet *ppkt, Packet *spkt,
+                                 uint16_t poff, uint16_t soff,
+                                 uint16_t len)
+{
+    if (memcmp(ppkt->data + poff, spkt->data + soff, len)) {
+        trace_colo_compare_main("the payload is not same");
+        return false;
+    }
+    return true;
+}
+
+/*
+ * return true means that the payload is consist and
+ * need to make the next comparison, false means do
+ * the checkpoint
+ */
+static bool colo_mark_tcp_pkt(Packet *ppkt, Packet *spkt,
+                              int8_t *mark, uint32_t max_ack)
+{
+    *mark = 0;
+
+    if (ppkt->tcp_seq == spkt->tcp_seq && ppkt->seq_end == spkt->seq_end) {
+        if (colo_compare_payload(ppkt, spkt, ppkt->hdsize, spkt->hdsize,
+                                 ppkt->hdsize)) {
+            *mark = COLO_COMPARE_FREE_SECONDARY | COLO_COMPARE_FREE_PRIMARY;
+            return true;
+        }
+    }
+
+    /* one part of secondary packet payload still need to be compared */
+    if (!after(ppkt->seq_end, spkt->seq_end)) {
+        if (colo_compare_payload(ppkt, spkt, ppkt->hdsize + ppkt->offset,
+                                 spkt->hdsize + spkt->offset,
+                                 ppkt->pdsize - ppkt->offset)) {
+            if (!after(ppkt->tcp_ack, max_ack)) {
+                *mark = COLO_COMPARE_FREE_PRIMARY;
+                spkt->offset += ppkt->pdsize - ppkt->offset;
+                return true;
+            } else {
+                /* secondary guest hasn't ack the data, don't send
+                 * out this packet
+                 */
+                return false;
+            }
+        }
+    } else {
+        /* primary packet is longer than secondary packet, compare
+         * the same part and mark the primary packet offset
+         */
+        if (colo_compare_payload(ppkt, spkt, ppkt->hdsize + ppkt->offset,
+                                 spkt->hdsize + spkt->offset,
+                                 spkt->pdsize - spkt->offset)) {
+            *mark = COLO_COMPARE_FREE_SECONDARY;
+            ppkt->offset += spkt->pdsize - spkt->offset;
+            return true;
+        }
+    }
+
+    return false;
+}
+
+static void colo_compare_tcp(CompareState *s, Connection *conn)
+{
+    Packet *ppkt = NULL, *spkt = NULL;
+    int8_t mark;
+    uint32_t max_ack = conn->pack > conn->sack ? conn->sack : conn->pack;
+
+pri:
+    if (g_queue_is_empty(&conn->primary_list)) {
+        return;
+    }
+    ppkt = g_queue_pop_head(&conn->primary_list);
+sec:
+    if (g_queue_is_empty(&conn->secondary_list)) {
+        g_queue_push_head(&conn->primary_list, ppkt);
+        return;
+    }
+    spkt = g_queue_pop_head(&conn->secondary_list);
+
+    if (ppkt->tcp_seq == ppkt->seq_end) {
+        colo_release_primary_pkt(s, ppkt);
+        ppkt = NULL;
+    }
+
+    if (ppkt && conn->compare_seq && !after(ppkt->seq_end, conn->compare_seq)) 
{
+        trace_colo_compare_main("pri: pkt has compared & posted, destroy");
+        packet_destroy(ppkt, NULL);
+        ppkt = NULL;
+    }
+
+    if (spkt->tcp_seq == spkt->seq_end) {
+        packet_destroy(spkt, NULL);
+        if (!ppkt) {
+            goto pri;
+        } else {
+            goto sec;
+        }
+    } else {
+        if (conn->compare_seq && !after(spkt->seq_end, conn->compare_seq)) {
+            trace_colo_compare_main("sec: pkt has compared & posted, destroy");
+            packet_destroy(spkt, NULL);
+            if (!ppkt) {
+                goto pri;
+            } else {
+                goto sec;
+            }
+        }
+        if (!ppkt) {
+            g_queue_push_head(&conn->secondary_list, spkt);
+            goto pri;
+        }
+    }
+
+    if (colo_mark_tcp_pkt(ppkt, spkt, &mark, max_ack)) {
+        if (mark == COLO_COMPARE_FREE_PRIMARY) {
+            conn->compare_seq = ppkt->seq_end;
+            colo_release_primary_pkt(s, ppkt);
+            g_queue_push_head(&conn->secondary_list, spkt);
+            goto pri;
+        }
+        if (mark == COLO_COMPARE_FREE_SECONDARY) {
+            conn->compare_seq = spkt->seq_end;
+            packet_destroy(spkt, NULL);
+            goto sec;
+        }
+        if (mark == (COLO_COMPARE_FREE_PRIMARY | COLO_COMPARE_FREE_SECONDARY)) 
{
+            conn->compare_seq = ppkt->seq_end;
+            colo_release_primary_pkt(s, ppkt);
+            packet_destroy(spkt, NULL);
+            goto pri;
+        }
+    } else {
+        g_queue_push_head(&conn->primary_list, ppkt);
+        g_queue_push_head(&conn->secondary_list, spkt);
+
+        /*
+         * colo_compare_inconsistent_notify();
+         * TODO: notice to checkpoint();
+         */
+    }
+}
+
 /*
  * The IP packets sent by primary and secondary
  * will be compared in here
@@ -224,110 +405,6 @@ static int colo_packet_compare_common(Packet *ppkt,
 
 /*
  * Called from the compare thread on the primary
- * for compare tcp packet
- * compare_tcp copied from Dr. David Alan Gilbert's branch
- */
-static int colo_packet_compare_tcp(Packet *spkt, Packet *ppkt)
-{
-    struct tcphdr *ptcp, *stcp;
-    int res;
-
-    trace_colo_compare_main("compare tcp");
-
-    ptcp = (struct tcphdr *)ppkt->transport_header;
-    stcp = (struct tcphdr *)spkt->transport_header;
-
-    /*
-     * The 'identification' field in the IP header is *very* random
-     * it almost never matches.  Fudge this by ignoring differences in
-     * unfragmented packets; they'll normally sort themselves out if different
-     * anyway, and it should recover at the TCP level.
-     * An alternative would be to get both the primary and secondary to rewrite
-     * somehow; but that would need some sync traffic to sync the state
-     */
-    if (ntohs(ppkt->ip->ip_off) & IP_DF) {
-        spkt->ip->ip_id = ppkt->ip->ip_id;
-        /* and the sum will be different if the IDs were different */
-        spkt->ip->ip_sum = ppkt->ip->ip_sum;
-    }
-
-    /*
-     * Check tcp header length for tcp option field.
-     * th_off > 5 means this tcp packet have options field.
-     * The tcp options maybe always different.
-     * for example:
-     * From RFC 7323.
-     * TCP Timestamps option (TSopt):
-     * Kind: 8
-     *
-     * Length: 10 bytes
-     *
-     *    +-------+-------+---------------------+---------------------+
-     *    |Kind=8 |  10   |   TS Value (TSval)  |TS Echo Reply (TSecr)|
-     *    +-------+-------+---------------------+---------------------+
-     *       1       1              4                     4
-     *
-     * In this case the primary guest's timestamp always different with
-     * the secondary guest's timestamp. COLO just focus on payload,
-     * so we just need skip this field.
-     */
-    if (ptcp->th_off > 5) {
-        ptrdiff_t ptcp_offset, stcp_offset;
-
-        ptcp_offset = ppkt->transport_header - (uint8_t *)ppkt->data
-                      + (ptcp->th_off * 4) - ppkt->vnet_hdr_len;
-        stcp_offset = spkt->transport_header - (uint8_t *)spkt->data
-                      + (stcp->th_off * 4) - spkt->vnet_hdr_len;
-
-        /*
-         * When network is busy, some tcp options(like sack) will unpredictable
-         * occur in primary side or secondary side. it will make packet size
-         * not same, but the two packet's payload is identical. colo just
-         * care about packet payload, so we skip the option field.
-         */
-        res = colo_packet_compare_common(ppkt, spkt, ptcp_offset, stcp_offset);
-    } else if (ptcp->th_sum == stcp->th_sum) {
-        res = colo_packet_compare_common(ppkt, spkt, ETH_HLEN, ETH_HLEN);
-    } else {
-        res = -1;
-    }
-
-    if (res != 0 &&
-        trace_event_get_state_backends(TRACE_COLO_COMPARE_MISCOMPARE)) {
-        char pri_ip_src[20], pri_ip_dst[20], sec_ip_src[20], sec_ip_dst[20];
-
-        strcpy(pri_ip_src, inet_ntoa(ppkt->ip->ip_src));
-        strcpy(pri_ip_dst, inet_ntoa(ppkt->ip->ip_dst));
-        strcpy(sec_ip_src, inet_ntoa(spkt->ip->ip_src));
-        strcpy(sec_ip_dst, inet_ntoa(spkt->ip->ip_dst));
-
-        trace_colo_compare_ip_info(ppkt->size, pri_ip_src,
-                                   pri_ip_dst, spkt->size,
-                                   sec_ip_src, sec_ip_dst);
-
-        trace_colo_compare_tcp_info("pri tcp packet",
-                                    ntohl(ptcp->th_seq),
-                                    ntohl(ptcp->th_ack),
-                                    res, ptcp->th_flags,
-                                    ppkt->size);
-
-        trace_colo_compare_tcp_info("sec tcp packet",
-                                    ntohl(stcp->th_seq),
-                                    ntohl(stcp->th_ack),
-                                    res, stcp->th_flags,
-                                    spkt->size);
-
-        qemu_hexdump((char *)ppkt->data, stderr,
-                     "colo-compare ppkt", ppkt->size);
-        qemu_hexdump((char *)spkt->data, stderr,
-                     "colo-compare spkt", spkt->size);
-    }
-
-    return res;
-}
-
-/*
- * Called from the compare thread on the primary
  * for compare udp packet
  */
 static int colo_packet_compare_udp(Packet *spkt, Packet *ppkt)
@@ -492,14 +569,15 @@ static void colo_compare_connection(void *opaque, void 
*user_data)
     GList *result = NULL;
     int ret;
 
+    if (conn->ip_proto == IPPROTO_TCP) {
+        colo_compare_tcp(s, conn);
+        return;
+    }
+
     while (!g_queue_is_empty(&conn->primary_list) &&
            !g_queue_is_empty(&conn->secondary_list)) {
         pkt = g_queue_pop_head(&conn->primary_list);
         switch (conn->ip_proto) {
-        case IPPROTO_TCP:
-            result = g_queue_find_custom(&conn->secondary_list,
-                     pkt, (GCompareFunc)colo_packet_compare_tcp);
-            break;
         case IPPROTO_UDP:
             result = g_queue_find_custom(&conn->secondary_list,
                      pkt, (GCompareFunc)colo_packet_compare_udp);
diff --git a/net/colo.c b/net/colo.c
index a39d600..1743522 100644
--- a/net/colo.c
+++ b/net/colo.c
@@ -138,6 +138,8 @@ Connection *connection_new(ConnectionKey *key)
     conn->processing = false;
     conn->offset = 0;
     conn->syn_flag = 0;
+    conn->pack = 0;
+    conn->sack = 0;
     g_queue_init(&conn->primary_list);
     g_queue_init(&conn->secondary_list);
 
@@ -163,6 +165,12 @@ Packet *packet_new(const void *data, int size, int 
vnet_hdr_len)
     pkt->size = size;
     pkt->creation_ms = qemu_clock_get_ms(QEMU_CLOCK_HOST);
     pkt->vnet_hdr_len = vnet_hdr_len;
+    pkt->tcp_seq = 0;
+    pkt->tcp_ack = 0;
+    pkt->seq_end = 0;
+    pkt->hdsize = 0;
+    pkt->pdsize = 0;
+    pkt->offset = 0;
 
     return pkt;
 }
diff --git a/net/colo.h b/net/colo.h
index 0658e86..97bc41e 100644
--- a/net/colo.h
+++ b/net/colo.h
@@ -45,6 +45,14 @@ typedef struct Packet {
     int64_t creation_ms;
     /* Get vnet_hdr_len from filter */
     uint32_t vnet_hdr_len;
+    uint32_t tcp_seq; /* sequence number */
+    uint32_t tcp_ack; /* acknowledgement number */
+    /* the sequence number of the last byte of the packet */
+    uint32_t seq_end;
+    uint8_t hdsize;  /* the header length */
+    uint16_t pdsize; /* the payload length */
+    /* record the payload offset(the length that has been compared) */
+    uint16_t offset;
 } Packet;
 
 typedef struct ConnectionKey {
@@ -64,6 +72,12 @@ typedef struct Connection {
     /* flag to enqueue unprocessed_connections */
     bool processing;
     uint8_t ip_proto;
+    /* record the sequence number that has been compared */
+    uint32_t compare_seq;
+    /* the maximum of acknowledgement number in primary_list queue */
+    uint32_t pack;
+    /* the maximum of acknowledgement number in secondary_list queue */
+    uint32_t sack;
     /* offset = secondary_seq - primary_seq */
     tcp_seq  offset;
     /*
-- 
2.9.4