MINOR: config: disable busy polling on old processes

in the context of seamless reload and busy polling, older processes will
create unecessary cpu conflicts; we can assume there is no need for busy
polling for old processes which are waiting to be terminated.

This patch is not a bug fix itself but might be a good stability
improvment when you are un the context of frequent seamless reloads with
a high "hard-stop-after" value; for that reasons I think this patch
should be backported in all 2.x versions.

Signed-off-by: William Dauchy <w.dauchy@criteo.com>

diff --git a/doc/configuration.txt b/doc/configuration.txt
index bfc8b9030e4fbe9741db50bb3ce14a67c4417927..9bc7d7150b4f0a1d3b73aab0dfb55413267b57a7 100644 (file)
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -1476,6 +1476,10 @@ busy-polling
   prefixing it with the "no" keyword. It is ignored by the "select" and
   "poll" pollers.
 
+  This option is automatically disabled on old processes in the context of
+  seamless reload; it avoids too much cpu conflicts when multiple processes
+  stay around for some time waiting for the end of their current connections.
+
 max-spread-checks <delay in milliseconds>
   By default, haproxy tries to spread the start of health checks across the
   smallest health check interval of all the servers in a farm. The principle is

diff --git a/src/proxy.c b/src/proxy.c
index a5570dafa0718580df43b9af59c96a1f6f0e55fd..9448d1a3e7cc221efc1b5890594b312a3ebffde1 100644 (file)
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -1116,6 +1116,8 @@ void soft_stop(void)
        struct task *task;
 
        stopping = 1;
+       /* disable busy polling to avoid cpu eating for the new process */
+       global.tune.options &= ~GTUNE_BUSY_POLLING;
        if (tick_isset(global.hard_stop_after)) {
                task = task_new(MAX_THREADS_MASK);
                if (task) {