server: server loop will exhaust data inputs before sleeping

By exhausting data on input, the performance will be more
consistent + the code more clearly distinguishes between
polling and processing. A test showed gdb packet load
performance go from ~1550kByte/s to 1650kBytes/s + being
more stable.

Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>

diff --git a/src/server/server.c b/src/server/server.c
index 75a6bed08be6dcb48532c4b7b10561e9031a5877..f762704dd3412f6c6761aeca0c14518311093626 100644 (file)
--- a/src/server/server.c
+++ b/src/server/server.c
@@ -292,9 +292,10 @@ int server_loop(struct command_context *command_context)
 {
        struct service *service;
 
+       bool poll = true;
+
        /* used in select() */
        fd_set read_fds;
-       struct timeval tv;
        int fd_max;
 
        /* used in accept() */
@@ -305,10 +306,6 @@ int server_loop(struct command_context *command_context)
                LOG_ERROR("couldn't set SIGPIPE to SIG_IGN");
 #endif
 
-       /* do regular tasks after at most 10ms */
-       tv.tv_sec = 0;
-       tv.tv_usec = 10000;
-
        while (!shutdown_openocd)
        {
                /* monitor sockets for activity */
@@ -351,12 +348,24 @@ int server_loop(struct command_context *command_context)
 #endif
 #endif
 
-               openocd_sleep_prelude();
-               kept_alive();
-
-               /* Only while we're sleeping we'll let others run */
-               retval = socket_select(fd_max + 1, &read_fds, NULL, NULL, &tv);
-               openocd_sleep_postlude();
+               struct timeval tv;
+               tv.tv_sec = 0;
+               if (poll)
+               {
+                       /* we're just polling this iteration, this is faster on embedded
+                        * hosts */
+                       tv.tv_usec = 0;
+                       retval = socket_select(fd_max + 1, &read_fds, NULL, NULL, &tv);
+               } else
+               {
+                       /* Every 100ms */
+                       tv.tv_usec = 100000;
+                       /* Only while we're sleeping we'll let others run */
+                       openocd_sleep_prelude();
+                       kept_alive();
+                       retval = socket_select(fd_max + 1, &read_fds, NULL, NULL, &tv);
+                       openocd_sleep_postlude();
+               }
 
                if (retval == -1)
                {
@@ -385,15 +394,20 @@ int server_loop(struct command_context *command_context)
 #endif
                }
 
-               target_call_timer_callbacks();
-               process_jim_events(command_context);
-
                if (retval == 0)
                {
-                       /* do regular tasks after at most 100ms */
-                       tv.tv_sec = 0;
-                       tv.tv_usec = 10000;
+                       /* We only execute these callbacks when there was nothing to do or we timed out */
+                       target_call_timer_callbacks();
+                       process_jim_events(command_context);
+
                        FD_ZERO(&read_fds); /* eCos leaves read_fds unchanged in this case!  */
+
+                       /* We timed out/there was nothing to do, timeout rather than poll next time */
+                       poll = false;
+               } else
+               {
+                       /* There was something to do, next time we'll just poll */
+                       poll = true;
                }
 
                for (service = services; service; service = service->next)