Re: [PATCH] xen, xen-sparse: modify spinlocks to use directed yield

[Ryan Harper <ryanh@us.ibm.com>]

* Ryan Harper <ryanh@us.ibm.com> [2005-05-20 11:55]:
> The following patch creates a new hypercall, do_confer() which allows a

Here is a debug patch I've been using to go along with it. Comment out
the printks in the do_confer() routine if you are measuring performance.

--
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253   T/L: 678-9253
ryanh@us.ibm.com


diffstat output:
 common/keyhandler.c |   30 ++++++++++++++++++++++++++++++
 common/schedule.c   |   19 ++++++++++++++++---
 include/xen/sched.h |    3 +++
 3 files changed, 49 insertions(+), 3 deletions(-)

Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
---
diff -urN confer/xen/common/keyhandler.c debug/xen/common/keyhandler.c
--- confer/xen/common/keyhandler.c	2005-05-19 22:20:27.000000000 -0500
+++ debug/xen/common/keyhandler.c	2005-05-20 10:39:03.565845280 -0500
@@ -11,6 +11,7 @@
 #include <xen/sched.h>
 #include <xen/softirq.h>
 #include <asm/debugger.h>
+#include <public/xen.h>
 
 #define KEY_MAX 256
 #define STR_MAX  64
@@ -138,6 +139,33 @@
     read_unlock(&domlist_lock);
 }
 
+static void do_dump_confer(unsigned char key)
+{
+    struct domain *d;
+    struct exec_domain *ed;
+    s_time_t       now = NOW();
+
+    printk("'%c' pressed -> dumping confer stats (now=0x%X:%08X)\n", key,
+           (u32)(now>>32), (u32)now);
+
+    read_lock(&domlist_lock);
+    for_each_domain ( d )
+    {
+        for_each_exec_domain ( d, ed )
+        {
+            printk("Xen: DOM %d, VCPU %d, CPU %d,"
+                   " confers %d, confer_out %d,"
+                   " confer_in %d, yield_count %d\n",
+                   d->domain_id, ed->vcpu_id, ed->processor,
+                   ed->confercnt, ed->confer_out, 
+                   ed->confer_in, ed->vcpu_info->yield_count
+                  );
+        }
+
+    }
+    read_unlock(&domlist_lock);
+}
+
 extern void dump_runq(unsigned char key);
 extern void print_sched_histo(unsigned char key);
 extern void reset_sched_histo(unsigned char key);
@@ -183,6 +211,8 @@
     register_keyhandler(
         'q', do_task_queues, "dump task queues + guest state");
     register_keyhandler(
+        'c', do_dump_confer, "dump confer stats");
+    register_keyhandler(
         'r', dump_runq,      "dump run queues");
     register_irq_keyhandler(
         'R', halt_machine,   "reboot machine"); 
diff -urN confer/xen/common/schedule.c debug/xen/common/schedule.c
--- confer/xen/common/schedule.c	2005-05-20 10:37:58.367756896 -0500
+++ debug/xen/common/schedule.c	2005-05-20 10:39:03.575843760 -0500
@@ -228,7 +228,11 @@
         if ( test_bit(_VCPUF_conferring, &current->vcpu_flags) ) {
             clear_bit(_VCPUF_conferring, &current->vcpu_flags);
             set_bit(_VCPUF_conferred, &current->vcpu_flags);
+            /* increment confer counters */
+            current->confer_out++;
+            ed->confer_in++;
         }
+
         SCHED_OP(wake, ed);
 #ifdef WAKE_HISTO
         ed->wokenup = NOW();
@@ -283,6 +287,9 @@
 {
     struct domain *d = current->domain;
    
+    /* count hcalls */
+    current->confercnt++;
+
     /* Validate CONFER prereqs:
     * - vcpu is within bounds
     * - vcpu is a valid in this domain
@@ -299,16 +306,22 @@
     if (d->exec_domain[vcpu] == NULL)
         return 0;
 
-    if (!test_bit(_VCPUF_canconfer, &current->vcpu_flags))
+    if (!test_bit(_VCPUF_canconfer, &current->vcpu_flags)) {
+        printk("confer: canconfer not set, %d->vcpu-flags = 0x%08lx\n", current->vcpu_id, current->vcpu_flags);
         return 0;
+    }
 
     /* even counts indicate a running vcpu, odd is preempted/conferred */
     /* don't confer if holder is currently running */
-    if ((d->exec_domain[vcpu]->vcpu_info->yield_count & 1) == 0)
+    if ((d->exec_domain[vcpu]->vcpu_info->yield_count & 1) == 0) {
+        printk("confer: vcpu %d already running\n", vcpu);
         return 0;
+    }
 
-    if (d->exec_domain[vcpu]->vcpu_info->yield_count != yield_count)
+    if (d->exec_domain[vcpu]->vcpu_info->yield_count != yield_count) {
+        printk("confer: yield_count mismatch\n");
         return 0;
+    }
 
     /*
      * set current's state to conferring, wake target
diff -urN confer/xen/include/xen/sched.h debug/xen/include/xen/sched.h
--- confer/xen/include/xen/sched.h	2005-05-20 10:37:58.378755224 -0500
+++ debug/xen/include/xen/sched.h	2005-05-20 10:39:03.577843456 -0500
@@ -87,6 +87,9 @@
     atomic_t         pausecnt;
 
     cpumap_t         cpumap;        /* which cpus this domain can run on */
+    u32              confer_out;    /* inc when conferring to another vcpu */
+    u32              confer_in;     /* inc when conferred from another vcpu */
+    u32              confercnt;     /* # of do_confer hcalls */
 
     struct arch_exec_domain arch;
 };