This is a set of changes which allow the tracebuffer functionality to

be enabled and disabled dynamically while the system is running. The
existing DOM0_TBUFCONTROL hypercall is used, and three new operations
have been added: enable, disable, and set_size. This is to address
concerns that use of the trace buffers impacts system performance.

The initial value of opt_tbuf_size is set to zero, so that trace
buffers remain disabled by default. They can be enabled as they used
to be, by adding tbuf_size= to the xen command line at boot time. They
can also be turned on and off any time when the system is running. The
size of the trace buffer allocation can also be changed dynamically
while the system is running. The trace buffers may be completely
deallocated by setting the size to zero. No change in buffer size can
be done while tracing is enabled;

Other Changes made:
 - Update the constants in tools/xentrace/formats to match those in 
public/trace.h
 - libxc functions for enable/disable, get/set size
Still left to do:
 - remove all ifdef's for trace buffers and the 'trace' build option
 - xm command to do enable/disable trace buffers and get/set size
 
Signed-off-by: Rob Gardner  <rob.gardner@hp.com>

7 files changed, 170 insertions, 15 deletions

diff --git a/tools/libxc/Makefile b/tools/libxc/Makefile
index 9c4b705641..b1d91d157d 100644
--- a/tools/libxc/Makefile
+++ b/tools/libxc/Makefile
@@ -23,6 +23,7 @@ SRCS       += xc_misc.c
 SRCS       += xc_physdev.c
 SRCS       += xc_private.c
 SRCS       += xc_sedf.c
+SRCS       += xc_tbuf.c
 BUILD_SRCS += xc_linux_build.c
 BUILD_SRCS += xc_load_bin.c
 BUILD_SRCS += xc_load_elf.c
diff --git a/tools/libxc/xc_tbuf.c b/tools/libxc/xc_tbuf.c
new file mode 100644
index 0000000000..b47cde2867
--- /dev/null
+++ b/tools/libxc/xc_tbuf.c
@@ -0,0 +1,51 @@
+/******************************************************************************
+ * xc_tbuf.c
+ * 
+ * API for manipulating and accessing trace buffer parameters
+ * 
+ * Copyright (c) 2005, Rob Gardner
+ */
+
+#include "xc_private.h"
+
+int xc_tbuf_enable(int xc_handle, int enable)
+{
+  dom0_op_t op;
+
+  op.cmd = DOM0_TBUFCONTROL;
+  op.interface_version = DOM0_INTERFACE_VERSION;
+  if (enable)
+    op.u.tbufcontrol.op  = DOM0_TBUF_ENABLE;
+  else
+    op.u.tbufcontrol.op  = DOM0_TBUF_DISABLE;
+  
+  return xc_dom0_op(xc_handle, &op);
+}
+
+int xc_tbuf_set_size(int xc_handle, uint32_t size)
+{
+  dom0_op_t op;
+
+  op.cmd = DOM0_TBUFCONTROL;
+  op.interface_version = DOM0_INTERFACE_VERSION;
+  op.u.tbufcontrol.op  = DOM0_TBUF_SET_SIZE;
+  op.u.tbufcontrol.size = size;
+  
+  return xc_dom0_op(xc_handle, &op);
+}
+  
+int xc_tbuf_get_size(int xc_handle, uint32_t *size)
+{
+  int rc;
+  dom0_op_t op;
+
+  op.cmd = DOM0_TBUFCONTROL;
+  op.interface_version = DOM0_INTERFACE_VERSION;
+  op.u.tbufcontrol.op  = DOM0_TBUF_GET_INFO;
+
+  rc = xc_dom0_op(xc_handle, &op);
+  if (rc == 0)
+    *size = op.u.tbufcontrol.size;
+  return rc;
+}
+
diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
index ffbe4fdfff..42ce3097be 100644
--- a/tools/libxc/xenctrl.h
+++ b/tools/libxc/xenctrl.h
@@ -149,7 +149,7 @@ int xc_domain_dumpcore(int xc_handle,
                        const char *corename);
 
 /*
- * This function sets the maximum number vcpus that a domian may create.
+ * This function sets the maximum number of vcpus that a domain may create.
  *
  * @parm xc_handle a handle to an open hypervisor interface.
  * @parm domid the domain id in which vcpus are to be created.
@@ -490,6 +490,47 @@ int xc_gnttab_dump_table(int        xc_handle,
 /* Get current total pages allocated to a domain. */
 long xc_get_tot_pages(int xc_handle, uint32_t domid);
 
+
+/*
+ * Trace Buffer Operations
+ */
+
+/**
+ * This function enables or disables tracing. Trace buffer memory must
+ * be already allocated by setting the size to a non-zero value, otherwise
+ * tracing cannot be enabled.
+ *
+ * @parm xc_handle a handle to an open hypervisor interface
+ * @parm enable the desired action, 1 for enable, 0 for disable
+ * @return 0 on success, -1 on failure.
+ */
+int xc_tbuf_enable(int xc_handle, int enable);
+
+/**
+ * This function sets the size of the trace buffers. Setting it to zero
+ * deallocates the memory used for trace buffers, and setting it to a
+ * non-zero value specifies the number of pages per cpu to allocate.
+ * To change the size of an existing allocation, you must first deallocate
+ * it then reallocate it. No change in size is allowed when tracing is
+ * enabled; A disable call must be made first.
+ *
+ * @parm xc_handle a handle to an open hypervisor interface
+ * @parm size the size in pages per cpu for the trace buffers
+ * @return 0 on success, -1 on failure.
+ */
+int xc_tbuf_set_size(int xc_handle, uint32_t size);
+
+/**
+ * This function retrieves the current size of the trace buffers. 
+ * Note that the size returned is in terms of bytes, not pages.
+
+ * @parm xc_handle a handle to an open hypervisor interface
+ * @parm size will contain the size in bytes for the trace buffers
+ * @return 0 on success, -1 on failure.
+ */
+int xc_tbuf_get_size(int xc_handle, uint32_t *size);
+
+
 /* Execute a privileged dom0 operation. */
 int xc_dom0_op(int xc_handle, dom0_op_t *op);
 
diff --git a/tools/xentrace/Makefile b/tools/xentrace/Makefile
index b6ae508d85..5c3a77be83 100644
--- a/tools/xentrace/Makefile
+++ b/tools/xentrace/Makefile
@@ -14,7 +14,7 @@ CFLAGS  += -I $(XEN_LIBXC)
 HDRS     = $(wildcard *.h)
 OBJS     = $(patsubst %.c,%.o,$(wildcard *.c))
 
-BIN      = xentrace
+BIN      = xentrace tbctl setsize
 SCRIPTS  = xentrace_format
 MAN1     = $(wildcard *.1)
 MAN8     = $(wildcard *.8)
diff --git a/tools/xentrace/formats b/tools/xentrace/formats
index 78954b9543..818eef1c60 100644
--- a/tools/xentrace/formats
+++ b/tools/xentrace/formats
@@ -1,16 +1,16 @@
-0x00020001	CPU%(cpu)d	%(tsc)d		sched_add_domain	[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
-0x00020002	CPU%(cpu)d	%(tsc)d		sched_rem_domain	[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
-0x00020003	CPU%(cpu)d	%(tsc)d		domain_sleep		[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
-0x00020004	CPU%(cpu)d	%(tsc)d		domain_wake		[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
-0x00020005	CPU%(cpu)d	%(tsc)d		do_yield		[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
-0x00020006	CPU%(cpu)d	%(tsc)d		do_block		[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
-0x00020007	CPU%(cpu)d	%(tsc)d		domain_shutdown		[ domid = 0x%(1)08x, edomid = 0x%(2)08x, reason = 0x%(3)08x ]
-0x00020008	CPU%(cpu)d	%(tsc)d		sched_ctl
-0x00020009	CPU%(cpu)d	%(tsc)d		sched_adjdom		[ domid = 0x%(1)08x ]
-0x0002000a	CPU%(cpu)d	%(tsc)d		__enter_scheduler	[ prev<domid:edomid> = 0x%(1)08x : 0x%(2)08x, next<domid:edomid> = 0x%(3)08x : 0x%(4)08x ]
-0x0002000B	CPU%(cpu)d	%(tsc)d		s_timer_fn
-0x0002000c	CPU%(cpu)d	%(tsc)d		t_timer_fn
-0x0002000d	CPU%(cpu)d	%(tsc)d		dom_timer_fn
+0x0002f001	CPU%(cpu)d	%(tsc)d		sched_add_domain	[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
+0x0002f002	CPU%(cpu)d	%(tsc)d		sched_rem_domain	[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
+0x0002f003	CPU%(cpu)d	%(tsc)d		domain_sleep		[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
+0x0002f004	CPU%(cpu)d	%(tsc)d		domain_wake		[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
+0x0002f005	CPU%(cpu)d	%(tsc)d		do_yield		[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
+0x0002f006	CPU%(cpu)d	%(tsc)d		do_block		[ domid = 0x%(1)08x, edomid = 0x%(2)08x ]
+0x0002f007	CPU%(cpu)d	%(tsc)d		domain_shutdown		[ domid = 0x%(1)08x, edomid = 0x%(2)08x, reason = 0x%(3)08x ]
+0x0002f008	CPU%(cpu)d	%(tsc)d		sched_ctl
+0x0002f009	CPU%(cpu)d	%(tsc)d		sched_adjdom		[ domid = 0x%(1)08x ]
+0x0002f00a	CPU%(cpu)d	%(tsc)d		__enter_scheduler	[ prev<domid:edomid> = 0x%(1)08x : 0x%(2)08x, next<domid:edomid> = 0x%(3)08x : 0x%(4)08x ]
+0x0002f00B	CPU%(cpu)d	%(tsc)d		s_timer_fn
+0x0002f00c	CPU%(cpu)d	%(tsc)d		t_timer_fn
+0x0002f00d	CPU%(cpu)d	%(tsc)d		dom_timer_fn
 
 0x00080001	CPU%(cpu)d      %(tsc)d		VMX_VMEXIT		[ domid = 0x%(1)08x, eip = 0x%(2)08x, reason = 0x%(3)08x ]
 0x00080002	CPU%(cpu)d      %(tsc)d		VMX_VECTOR		[ domid = 0x%(1)08x, eip = 0x%(2)08x, vector = 0x%(3)08x ]
diff --git a/tools/xentrace/setsize.c b/tools/xentrace/setsize.c
new file mode 100644
index 0000000000..0b5311ea57
--- /dev/null
+++ b/tools/xentrace/setsize.c
@@ -0,0 +1,36 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <xenctrl.h>
+
+int main(int argc, char * argv[])
+{
+  unsigned int size;
+  int xc_handle = xc_interface_open();
+  
+  if (xc_tbuf_get_size(xc_handle, &size) != 0) {
+    perror("Failure to get tbuf info from Xen. Guess size is 0.");
+    printf("This may mean that tracing is not compiled into xen.\n");
+    exit(1);
+  }
+  else
+    printf("Current tbuf size: 0x%x\n", size);
+  
+  if (argc < 2)
+    exit(0);
+
+  size = atoi(argv[1]);
+
+  if (xc_tbuf_set_size(xc_handle, size) != 0) {
+    perror("set_size Hypercall failure");
+    exit(1);
+  }
+  
+  if (xc_tbuf_get_size(xc_handle, &size) != 0)
+    perror("Failure to get tbuf info from Xen. Guess size is 0.");
+  else
+    printf("New tbuf size: 0x%x\n", size);
+  
+  xc_interface_close(xc_handle);
+  return 0;
+}
diff --git a/tools/xentrace/tbctl.c b/tools/xentrace/tbctl.c
new file mode 100644
index 0000000000..fd9dc3a9c8
--- /dev/null
+++ b/tools/xentrace/tbctl.c
@@ -0,0 +1,26 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <xenctrl.h>
+
+int main(int argc, char * argv[])
+{
+    int enable;
+    int xc_handle = xc_interface_open();
+    
+    if (argc < 2) {
+      printf("usage: %s [0|1]\n", argv[0]);
+      exit(1);
+    }
+    enable = atoi(argv[1]);
+
+    if (xc_tbuf_enable(xc_handle, enable) != 0) {
+        perror("Enable/Disable Hypercall failure");
+        exit(1);
+    }
+    else
+      printf("Tracing now %s\n", (enable ? "enabled" : "disabled"));
+
+    xc_interface_close(xc_handle);
+    return 0;
+}