[PATCH 0 of 3] xentrace updates

[PATCH 0 of 3] xentrace updates

[George Dunlap]

Some minor updates to xentrace.

[PATCH 1 of 3] xentrace: Skip to low cpu when throwing away portions of the circular buffer

[George Dunlap]

Skip to the next "low" cpu when throwing away portions of the circular
memory buffer.  This makes subsequent analysis easier.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>

diff -r 859a372efa66 -r 16ef34de0129 tools/xentrace/xentrace.c
--- a/tools/xentrace/xentrace.c	Tue Apr 13 13:40:58 2010 +0100
+++ b/tools/xentrace/xentrace.c	Tue Apr 13 17:24:07 2010 +0100
@@ -149,6 +149,7 @@
 {
     struct cpu_change_record *rec;
     long need_to_consume, free, freed;
+    int last_cpu = -1;
 
     if ( membuf.pending_size > 0 )
     {
@@ -193,11 +194,25 @@
 
         if ( need_to_consume > 0 )
         {
+            last_cpu = rec->data.cpu;
             MEMBUF_CONS_INCREMENT(freed);
             need_to_consume -= freed;
         }
     } while( need_to_consume > 0 );
 
+    /* For good tsc consistency, we need to start at a low-cpu buffer.  Keep
+     * skipping until the cpu goes down or stays the same. */
+    rec = (struct cpu_change_record *)MEMBUF_POINTER(membuf.cons);
+    while ( rec->data.cpu > last_cpu )
+    {
+        last_cpu = rec->data.cpu; 
+
+        freed = sizeof(*rec) + rec->data.window_size;
+        
+        MEMBUF_CONS_INCREMENT(freed);
+        rec = (struct cpu_change_record *)MEMBUF_POINTER(membuf.cons);
+    }
+
 start_window:
     /*
      * Start writing "pending" data.  Update prod once all this data is

[PATCH 2 of 3] xentrace: Add an option not to enable tracing

[George Dunlap]

Add an option that will set up the buffers and listen for updates,
but will not enable tracing.  This is useful if you have hacks
in Xen to enable tracing at key points (for example, debugging a shadow
bug).

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>

diff -r 16ef34de0129 -r ce0812566a4d tools/xentrace/xentrace.c
--- a/tools/xentrace/xentrace.c	Tue Apr 13 17:24:07 2010 +0100
+++ b/tools/xentrace/xentrace.c	Tue Apr 13 17:24:08 2010 +0100
@@ -58,7 +58,8 @@
     unsigned long timeout;
     unsigned long memory_buffer;
     uint8_t discard:1,
-        disable_tracing:1;
+        disable_tracing:1,
+        start_disabled:1;
 } settings_t;
 
 struct t_struct {
@@ -659,6 +660,10 @@
 
     /* setup access to trace buffers */
     get_tbufs(&tbufs_mfn, &tinfo_size);
+
+    if ( opts.start_disabled )
+        disable_tbufs();
+    
     tbufs = map_tbufs(tbufs_mfn, num, tinfo_size);
 
     size = tbufs->t_info->tbuf_size * XC_PAGE_SIZE;
@@ -791,6 +796,9 @@
 "                          it exits. Selecting this option will tell it to\n" \
 "                          keep tracing on.  Traces will be collected in\n" \
 "                          Xen's trace buffers until they become full.\n" \
+"  -X  --start-disabled    Setup trace buffers and listen, but don't enable\n" \
+"                          tracing. (Useful if tracing will be enabled by\n" \
+"                          else.)\n" \
 "  -T  --time-interval=s   Run xentrace for s seconds and quit.\n" \
 "  -?, --help              Show this message\n" \
 "  -V, --version           Print program version\n" \
@@ -914,12 +922,13 @@
         { "memory-buffer",  required_argument, 0, 'M' },
         { "discard-buffers", no_argument,      0, 'D' },
         { "dont-disable-tracing", no_argument, 0, 'x' },
+        { "start-disabled", no_argument,       0, 'X' },
         { "help",           no_argument,       0, '?' },
         { "version",        no_argument,       0, 'V' },
         { 0, 0, 0, 0 }
     };
 
-    while ( (option = getopt_long(argc, argv, "t:s:c:e:S:r:T:M:Dx?V",
+    while ( (option = getopt_long(argc, argv, "t:s:c:e:S:r:T:M:DxX?V",
                     long_options, NULL)) != -1) 
     {
         switch ( option )
@@ -957,6 +966,10 @@
             opts.disable_tracing = 0;
             break;
 
+        case 'X': /* Start disabled */
+            opts.start_disabled = 1;
+            break;
+
         case 'T':
             opts.timeout = argtol(optarg, 0);
             break;
@@ -993,6 +1006,7 @@
     opts.cpu_mask = 0;
     opts.disk_rsvd = 0;
     opts.disable_tracing = 1;
+    opts.start_disabled = 0;
     opts.timeout = 0;
 
     parse_args(argc, argv);

[PATCH 3 of 3] xentrace: Add missing help option

[George Dunlap]

Describe the --reserve-disk-space option in the xentrace help.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>

diff -r ce0812566a4d -r a0d521070853 tools/xentrace/xentrace.c
--- a/tools/xentrace/xentrace.c	Tue Apr 13 17:24:08 2010 +0100
+++ b/tools/xentrace/xentrace.c	Tue Apr 13 17:24:08 2010 +0100
@@ -804,6 +804,9 @@
 "  -V, --version           Print program version\n" \
 "  -M, --memory-buffer=b   Copy trace records to a circular memory buffer.\n" \
 "                          Dump to file on exit.\n" \
+"  -r  --reserve-disk-space=n Before writing trace records to disk, check to see\n" \
+"                          that after the write there will be at least n space\n" \
+"                          left on the disk.\n" \
 "\n" \
 "This tool is used to capture trace buffer data from Xen. The\n" \
 "data is output in a binary format, in the following order:\n" \

[PATCH 0 of 3] xentrace updates

[Olaf Hering]

Three more minor corrections to trace.c. The formula used the already
calculated offset of the array for multiplication, and the max number of pages
per cpu could wrap.

However, its not possible to allocate the MAX_ORDER (which is 9 on x86) for
each cpu (just for verification) on a box with 8 cpus. If booted with
tbuf_size=8192 alloc fails on the 4th cpu, at runtime already on the second.
What is the reason for that, which pool of pages is too small?

Olaf