kernel - Record token & mplock collisions in thread->td_wmesg

* Record token & mplock collisions which the lwkt thread schedule spins
  on in the thread wmesg, which will show up in ps, top, etc.

  This makes it a lot more obvious when a thread is stalling on a token
  or the mplock and is generally superior to the old per-cpu collision
  record.

diff --git a/sys/kern/lwkt_thread.c b/sys/kern/lwkt_thread.c
index 6d32a6b..49f5ced 100644 (file)
--- a/sys/kern/lwkt_thread.c
+++ b/sys/kern/lwkt_thread.c
@@ -498,8 +498,6 @@ lwkt_switch(void)
     int mpheld;
 #endif
     int didaccumulate;
-    const char *lmsg;  /* diagnostic - 'systat -pv 1' */
-    const void *laddr;
 
     /*
      * Switching from within a 'fast' (non thread switched) interrupt or IPI
@@ -672,9 +670,10 @@ lwkt_switch(void)
        if (ntd->td_fairq_accum >= 0 &&
 #ifdef SMP
            (ntd->td_mpcount + ntd->td_xpcount == 0 ||
-            mpheld || cpu_try_mplock()) &&
+            mpheld || cpu_try_mplock_msg(&ntd->td_wmesg)) &&
 #endif
-           (!TD_TOKS_HELD(ntd) || lwkt_getalltokens(ntd, &lmsg, &laddr))
+           (!TD_TOKS_HELD(ntd) ||
+            lwkt_getalltokens(ntd))
        ) {
 #ifdef SMP
            clr_cpu_contention_mask(gd);
@@ -682,18 +681,11 @@ lwkt_switch(void)
            goto havethread;
        }
 
-       lmsg = NULL;
-       laddr = NULL;
-
 #ifdef SMP
        if (ntd->td_fairq_accum >= 0)
                set_cpu_contention_mask(gd);
        /* Reload mpheld (it become stale after mplock/token ops) */
        mpheld = MP_LOCK_HELD(gd);
-       if (ntd->td_mpcount + ntd->td_xpcount && mpheld == 0) {
-           lmsg = "mplock";
-           laddr = ntd->td_mplock_stallpc;
-       }
 #endif
 
        /*
@@ -778,9 +770,6 @@ lwkt_switch(void)
                 */
                if (didaccumulate)
                        break;          /* try again from the top, almost */
-               if (lmsg)
-                   strlcpy(cpu_time.cp_msg, lmsg, sizeof(cpu_time.cp_msg));
-               cpu_time.cp_stallpc = (uintptr_t)laddr;
                goto haveidle;
            }
 
@@ -794,9 +783,9 @@ lwkt_switch(void)
                user_pri_sched) && ntd->td_fairq_accum >= 0 &&
 #ifdef SMP
                (ntd->td_mpcount + ntd->td_xpcount == 0 ||
-                mpheld || cpu_try_mplock()) &&
+                mpheld || cpu_try_mplock_msg(&ntd->td_wmesg)) &&
 #endif
-               (!TD_TOKS_HELD(ntd) || lwkt_getalltokens(ntd, &lmsg, &laddr))
+               (!TD_TOKS_HELD(ntd) || lwkt_getalltokens(ntd))
            ) {
 #ifdef SMP
                    clr_cpu_contention_mask(gd);
@@ -809,17 +798,12 @@ lwkt_switch(void)
             * resources (tokens and/or mplock).
             */
 #ifdef SMP
-           ntd->td_wmesg = lmsg;
            if (ntd->td_fairq_accum >= 0)
                    set_cpu_contention_mask(gd);
            /*
             * Reload mpheld (it become stale after mplock/token ops).
             */
            mpheld = MP_LOCK_HELD(gd);
-           if (ntd->td_mpcount + ntd->td_xpcount && mpheld == 0) {
-               lmsg = "mplock";
-               laddr = ntd->td_mplock_stallpc;
-           }
            if (ntd->td_pri >= TDPRI_KERN_LPSCHED && ntd->td_fairq_accum >= 0)
                nquserok = 0;
 #endif

diff --git a/sys/kern/lwkt_token.c b/sys/kern/lwkt_token.c
index 18a930a..5d6fdb8 100644 (file)
--- a/sys/kern/lwkt_token.c
+++ b/sys/kern/lwkt_token.c
@@ -226,7 +226,7 @@ _lwkt_tokref_init(lwkt_tokref_t ref, lwkt_token_t tok, thread_t td)
  * Called from a critical section.
  */
 int
-lwkt_getalltokens(thread_t td, const char **msgp, const void **addrp)
+lwkt_getalltokens(thread_t td)
 {
        lwkt_tokref_t scan;
        lwkt_tokref_t ref;
@@ -267,8 +267,7 @@ lwkt_getalltokens(thread_t td, const char **msgp, const void **addrp)
                         * Otherwise we failed to acquire all the tokens.
                         * Undo and return.
                         */
-                       *msgp = tok->t_desc;
-                       *addrp = scan->tr_stallpc;
+                       td->td_wmesg = tok->t_desc;
                        atomic_add_long(&tok->t_collisions, 1);
                        lwkt_relalltokens(td);
                        return(FALSE);

diff --git a/sys/sys/mplock2.h b/sys/sys/mplock2.h
index 1f25fd1..1108993 100644 (file)
--- a/sys/sys/mplock2.h
+++ b/sys/sys/mplock2.h
@@ -21,6 +21,7 @@
 #define get_mplock()           get_mplock_debug(__FILE__, __LINE__)
 #define try_mplock()           try_mplock_debug(__FILE__, __LINE__)
 #define cpu_try_mplock()       cpu_try_mplock_debug(__FILE__, __LINE__)
+#define cpu_try_mplock_msg(lmsg) cpu_try_mplock_msg_debug(lmsg, __FILE__, __LINE__)
 
 void _get_mplock_predisposed(const char *file, int line);
 void _get_mplock_contested(const char *file, int line);
@@ -151,6 +152,18 @@ cpu_try_mplock_debug(const char *file, int line)
        return(1);
 }
 
+static __inline
+int
+cpu_try_mplock_msg_debug(const char **lmsg, const char *file, int line)
+{
+       if (cpu_try_mplock_debug(file, line)) {
+               return(1);
+       } else {
+               *lmsg = "mplock";
+               return(0);
+       }
+}
+
 /*
  * A cpu wanted the MP lock but could not get it.  This function is also
  * called directly from the LWKT scheduler.

diff --git a/sys/sys/thread.h b/sys/sys/thread.h
index 0477040..84eea7a 100644 (file)
--- a/sys/sys/thread.h
+++ b/sys/sys/thread.h
@@ -444,7 +444,7 @@ extern void lwkt_gettoken_hard(lwkt_token_t);
 extern int  lwkt_trytoken(lwkt_token_t);
 extern void lwkt_reltoken(lwkt_token_t);
 extern void lwkt_reltoken_hard(lwkt_token_t);
-extern int  lwkt_getalltokens(thread_t, const char **, const void **);
+extern int  lwkt_getalltokens(thread_t);
 extern void lwkt_relalltokens(thread_t);
 extern void lwkt_drain_token_requests(void);
 extern void lwkt_token_init(lwkt_token_t, int, const char *);