OPTIM: proxy: move atomically access fields out of the read-only ones

Perf top showed that h1_snd_buf() was having great difficulties accessing
the proxy's server_id_hdr_name field in the middle of the headers loop.
Moving the assignment out of the loop to a local variable moved the
problem there as well:

       |      if (!(h1m->flags & H1_MF_RESP) && isttest(h1c->px->server_id_hdr_n
  0.10 |20b0:   mov        -0x120(%rbp),%rdi
  1.33 |        mov        0x60(%rdi),%r10
  0.01 |        test       %eax,%eax
  0.18 |        jne        2118
 12.87 |        mov        0x350(%r10),%rdi
  0.01 |        test       %rdi,%rdi
  0.05 |        je         2118
       |        mov        0x358(%r10),%r11

It turns out that there are several atomically accessed fields in its
vicinity, causing the cache line to bounce all the time. Let's collect
the few frequently changed fields and place them together at the end
of the structure, and plug the 32-bit hole with another isolated field.
Doing so also reduced a little bit the cost of decrementing be->be_conn
in process_stream(), and overall the HTTP/1 performance increased by
about 1% both on ARM and x86_64.

diff --git a/include/haproxy/proxy-t.h b/include/haproxy/proxy-t.h
index 055141d0ff0f05904033b0b86d199af50c744d08..f02946552d9ded8f1b5c72983b3d2d0659527d4b 100644 (file)
--- a/include/haproxy/proxy-t.h
+++ b/include/haproxy/proxy-t.h
@@ -356,7 +356,8 @@ struct proxy {
        struct server *srv, *defsrv;            /* known servers; default server configuration */
        struct lbprm lbprm;                     /* load-balancing parameters */
        int srv_act, srv_bck;                   /* # of servers eligible for LB (UP|!checked) AND (enabled+weight!=0) */
-       int served;                             /* # of active sessions currently being served */
+       int load_server_state_from_file;        /* location of the file containing server state.
+                                                * flag PR_SRV_STATE_FILE_* */
        int  cookie_len;                        /* strlen(cookie_name), computed only once */
        struct server *ready_srv;               /* a server being ready to serve requests */
        char *cookie_domain;                    /* domain used to insert the cookie */
@@ -401,9 +402,6 @@ struct proxy {
        char *id;                               /* proxy id (name), indexed by <conf.name_node> below */
        char *desc;                             /* proxy description */
        struct proxy_per_tgroup *per_tgrp;      /* array of per-tgroup stuff such as queues */
-       unsigned int queueslength;              /* Sum of the length of each queue */
-       int totpend;                            /* total number of pending connections on this instance (for stats) */
-       unsigned int feconn, beconn;            /* # of active frontend and backends streams */
        unsigned int fe_sps_lim;                /* limit on new sessions per second on the frontend */
        unsigned int fullconn;                  /* #conns on backend above which servers are used at full load */
        struct ist server_id_hdr_name;                   /* the header to use to send the server id (name) */
@@ -495,8 +493,6 @@ struct proxy {
                struct email_alertq *queues;    /* per-mailer alerts queues */
        } email_alert;
 
-       int load_server_state_from_file;        /* location of the file containing server state.
-                                                * flag PR_SRV_STATE_FILE_* */
        char *server_state_file_name;           /* used when load_server_state_from_file is set to
                                                 * PR_SRV_STATE_FILE_LOCAL. Give a specific file name for
                                                 * this backend. If not specified or void, then the backend
@@ -508,6 +504,12 @@ struct proxy {
 
        EXTRA_COUNTERS(extra_counters_fe);
        EXTRA_COUNTERS(extra_counters_be);
+
+       THREAD_ALIGN(64);
+       unsigned int queueslength;              /* Sum of the length of each queue */
+       int served;                             /* # of active sessions currently being served */
+       int totpend;                            /* total number of pending connections on this instance (for stats) */
+       unsigned int feconn, beconn;            /* # of active frontend and backends streams */
 };
 
 struct switching_rule {