- scheduler: attempted performance enhancement.

Old: each scheduler process holds a semaphore
        while scanning the shared-mem job array.
        On machines with many CPUs
        there seems to be contention for this semaphore,
        causing slow scheduler response and possibly connection failures.
    New: Don't hold the semaphore while scanning array.
        Instead, if find a job that passes quick_check(),
        acquire the semaphore and recheck that the job is present in array
        and passes quick_check().
- client: show messages if app_config.xml has unrecognized tags

checkin_notes

@@ -7645,3 +7645,21 @@ David  12 Dec 2012
     - client: show Intel GPU memory size as integer
     lib/
         coproc.cpp
+
+David  12 Dec 2012
+    - scheduler: attempted performance enhancement.
+        Old: each scheduler process holds a semaphore
+            while scanning the shared-mem job array.
+            On machines with many CPUs
+            there seems to be contention for this semaphore,
+            causing slow scheduler response and possibly connection failures.
+        New: Don't hold the semaphore while scanning array.
+            Instead, if find a job that passes quick_check(),
+            acquire the semaphore and recheck that the job is present in array
+            and passes quick_check().
+    - client: show messages if app_config.xml has unrecognized tags
+
+    sched/
+        sched_array.cpp
+    client/
+        app_config.cpp,h

client/app_config.cpp

@@ -27,7 +27,7 @@
 
 bool have_max_concurrent = false;
 
-int APP_CONFIG::parse(XML_PARSER& xp) {
+int APP_CONFIG::parse(XML_PARSER& xp, PROJECT* p) {
     memset(this, 0, sizeof(APP_CONFIG));
 
     while (!xp.get_tag()) {
@@ -45,32 +45,46 @@ int APP_CONFIG::parse(XML_PARSER& xp) {
             }
             continue;
         }
+        if (log_flags.unparsed_xml) {
+            msg_printf(p, MSG_INFO,
+                "Unparsed line in app_info.xml: %s",
+                xp.parsed_tag
+            );
+        }
+        xp.skip_unexpected(log_flags.unparsed_xml, "APP_CONFIG::parse");
     }
     return ERR_XML_PARSE;
 }
 
-int APP_CONFIGS::parse(XML_PARSER& xp) {
+int APP_CONFIGS::parse(XML_PARSER& xp, PROJECT* p) {
     app_configs.clear();
     if (!xp.parse_start("app_config")) return ERR_XML_PARSE;
     while (!xp.get_tag()) {
         if (xp.match_tag("/app_config")) return 0;
         if (xp.match_tag("app")) {
             APP_CONFIG ac;
-            int retval = ac.parse(xp);
+            int retval = ac.parse(xp, p);
             if (!retval) {
                 app_configs.push_back(ac);
             }
             continue;
         }
+        if (log_flags.unparsed_xml) {
+            msg_printf(p, MSG_INFO,
+                "Unparsed line in app_info.xml: %s",
+                xp.parsed_tag
+            );
+        }
+        xp.skip_unexpected(log_flags.unparsed_xml, "APP_CONFIGS::parse");
     }
     return ERR_XML_PARSE;
 }
 
-int APP_CONFIGS::parse_file(FILE* f) {
+int APP_CONFIGS::parse_file(FILE* f, PROJECT* p) {
     MIOFILE mf;
     XML_PARSER xp(&mf);
     mf.init_file(f);
-    int retval = parse(xp);
+    int retval = parse(xp, p);
     return retval;
 }
 
@@ -115,7 +129,7 @@ void check_app_config() {
         msg_printf(p, MSG_INFO,
             "Found %s", APP_CONFIG_FILE_NAME
         );
-        int retval = p->app_configs.parse_file(f);
+        int retval = p->app_configs.parse_file(f, p);
         if (!retval) {
             p->app_configs.config_app_versions(p);
         }

client/app_config.h

@@ -33,14 +33,14 @@ struct APP_CONFIG {
     double gpu_gpu_usage;
     double gpu_cpu_usage;
 
-    int parse(XML_PARSER&);
+    int parse(XML_PARSER&, PROJECT*);
 };
 
 struct APP_CONFIGS {
     std::vector<APP_CONFIG> app_configs;
 
-    int parse(XML_PARSER&);
-    int parse_file(FILE*);
+    int parse(XML_PARSER&, PROJECT*);
+    int parse_file(FILE*, PROJECT*);
     void config_app_versions(PROJECT*);
 };
 

sched/sched_array.cpp

@@ -378,7 +378,12 @@ static bool scan_work_array() {
     bool no_more_needed = false;
     SCHED_DB_RESULT result;
 
-    lock_sema();
+    // To minimize the amount of time we lock the array,
+    // we initially scan without holding the lock.
+    // If we find a job that passes quick_check(),
+    // we acquire the lock and then check the job again.
+    //
+    bool sema_locked = false;
 
     rnd_off = rand() % ssp->max_wu_results;
     for (j=0; j<ssp->max_wu_results; j++) {
@@ -392,6 +397,7 @@ static bool scan_work_array() {
             );
         }
 
+recheck:
         if (wu_result.state != WR_STATE_PRESENT && wu_result.state != g_pid) {
             continue;
         }
@@ -424,6 +430,12 @@ static bool scan_work_array() {
             continue;
         }
 
+        if (!sema_locked) {
+            lock_sema();
+            sema_locked = true;
+            goto recheck;
+        }
+
         // mark wu_result as checked out and release semaphore.
         // from here on in this loop, don't continue on failure;
         // instead, goto dont_send (so that we reacquire semaphore)
@@ -434,6 +446,7 @@ static bool scan_work_array() {
 
         wu_result.state = g_pid;
         unlock_sema();
+        sema_locked = false;
 
         switch (slow_check(wu_result, app, bavp)) {
         case 1:
@@ -476,13 +489,14 @@ static bool scan_work_array() {
             }
             break;
         }
-        lock_sema();
         if (!work_needed(false)) {
             no_more_needed = true;
             break;
         }
     }
+    if (sema_locked) {
         unlock_sema();
+    }
     return no_more_needed;
 }