CLEANUP: global: reorder some fields to respect cache lines

Some entries are atomically updated by various threads, such as the
global counters, and they're mixed with others which are read all the
time like the mode. This explains why "perf" was seeing a huge access
cost on global.mode in process_stream()! Let's reorder them so that
the static config stuff is at the beginning and the live stuff is at
the end.

diff --git a/include/haproxy/global-t.h b/include/haproxy/global-t.h
index c19d069f0a67ce157f89ae223e32e5a13b6e7b98..21de8c3d45e25b1f90960d939d142136dd7fd0e8 100644 (file)
--- a/include/haproxy/global-t.h
+++ b/include/haproxy/global-t.h
@@ -91,6 +91,7 @@ struct global {
        int external_check;
        int nbproc;
        int nbthread;
+       int mode;
        unsigned int hard_stop_after;   /* maximum time allowed to perform a soft-stop */
        int maxconn, hardmaxconn;
        int maxsslconn;
@@ -100,21 +101,6 @@ struct global {
        int ssl_used_backend;       /* non-zero if SSL is used in a backend */
        int ssl_used_async_engines; /* number of used async engines */
        unsigned int ssl_server_verify; /* default verify mode on servers side */
-       struct freq_ctr conn_per_sec;
-       struct freq_ctr sess_per_sec;
-       struct freq_ctr ssl_per_sec;
-       struct freq_ctr ssl_fe_keys_per_sec;
-       struct freq_ctr ssl_be_keys_per_sec;
-       struct freq_ctr comp_bps_in;    /* bytes per second, before http compression */
-       struct freq_ctr comp_bps_out;   /* bytes per second, after http compression */
-       struct freq_ctr out_32bps;      /* #of 32-byte blocks emitted per second */
-       unsigned long long out_bytes;   /* total #of bytes emitted */
-       unsigned long long spliced_out_bytes; /* total #of bytes emitted though a kernel pipe */
-       int cps_lim, cps_max;
-       int sps_lim, sps_max;
-       int ssl_lim, ssl_max;
-       int ssl_fe_keys_max, ssl_be_keys_max;
-       unsigned int shctx_lookups, shctx_misses;
        int comp_rate_lim;           /* HTTP compression rate limit */
        int maxpipes;           /* max # of pipes */
        int maxsock;            /* max # of sockets */
@@ -122,9 +108,7 @@ struct global {
        int rlimit_memmax_all;  /* default all-process memory limit in megs ; 0=unset */
        int rlimit_memmax;      /* default per-process memory limit in megs ; 0=unset */
        long maxzlibmem;        /* max RAM for zlib in bytes */
-       int mode;
-       unsigned int req_count; /* request counter (HTTP or TCP session) for logs and unique_id */
-       int last_checks;
+
        int spread_checks;
        int max_spread_checks;
        int max_syslog_len;
@@ -173,7 +157,6 @@ struct global {
                } ux;
        } unix_bind;
        struct proxy *stats_fe;     /* the frontend holding the stats settings */
-       struct vars   vars;         /* list of variables for the process scope. */
 #ifdef USE_CPU_AFFINITY
        struct {
                unsigned long proc[MAX_PROCS];      /* list of CPU masks for the 32/64 first processes */
@@ -181,6 +164,33 @@ struct global {
                unsigned long thread[MAX_THREADS];  /* list of CPU masks for the 32/64 first threads of the 1st process */
        } cpu_map;
 #endif
+       /* The info above is config stuff, it doesn't change during the process' life */
+       /* A number of the elements below are updated by all threads in real time and
+        * suffer high contention, so we need to put them in their own cache lines, if
+        * possible grouped by changes.
+        */
+       ALWAYS_ALIGN(64);
+       struct freq_ctr conn_per_sec;
+       struct freq_ctr sess_per_sec;
+       struct freq_ctr ssl_per_sec;
+       struct freq_ctr ssl_fe_keys_per_sec;
+       struct freq_ctr ssl_be_keys_per_sec;
+       struct freq_ctr comp_bps_in;    /* bytes per second, before http compression */
+       struct freq_ctr comp_bps_out;   /* bytes per second, after http compression */
+       struct freq_ctr out_32bps;      /* #of 32-byte blocks emitted per second */
+       unsigned long long out_bytes;   /* total #of bytes emitted */
+       unsigned long long spliced_out_bytes; /* total #of bytes emitted though a kernel pipe */
+       int cps_lim, cps_max;
+       int sps_lim, sps_max;
+       int ssl_lim, ssl_max;
+       int ssl_fe_keys_max, ssl_be_keys_max;
+       unsigned int shctx_lookups, shctx_misses;
+       unsigned int req_count; /* request counter (HTTP or TCP session) for logs and unique_id */
+       int last_checks;
+       struct vars   vars;         /* list of variables for the process scope. */
+
+       /* leave this at the end to make sure we don't share this cache line by accident */
+       ALWAYS_ALIGN(64);
 };
 
 #endif /* _HAPROXY_GLOBAL_T_H */