Add new ktrace records for the start and end of VM faults. This gives

a pair of records similar to syscall entry and return that a user can
use to determine how long page faults take.  The new ktrace records are
enabled via the 'p' trace type, and are enabled in the default set of
trace points.

Reviewed by:	kib
MFC after:	2 weeks

3 files changed, 80 insertions, 2 deletions

diff --git a/sys/kern/kern_ktrace.c b/sys/kern/kern_ktrace.c
index 2c6e36c..363b8b8 100644
--- a/sys/kern/kern_ktrace.c
+++ b/sys/kern/kern_ktrace.c
@@ -101,6 +101,8 @@ struct ktr_request {
 		struct	ktr_genio ktr_genio;
 		struct	ktr_psig ktr_psig;
 		struct	ktr_csw ktr_csw;
+		struct	ktr_fault ktr_fault;
+		struct	ktr_faultend ktr_faultend;
 	} ktr_data;
 	STAILQ_ENTRY(ktr_request) ktr_list;
 };
@@ -119,6 +121,8 @@ static int data_lengths[] = {
 	sizeof(struct ktr_proc_ctor),		/* KTR_PROCCTOR */
 	0,					/* KTR_PROCDTOR */
 	sizeof(struct ktr_cap_fail),		/* KTR_CAPFAIL */
+	sizeof(struct ktr_fault),		/* KTR_FAULT */
+	sizeof(struct ktr_faultend),		/* KTR_FAULTEND */
 };
 
 static STAILQ_HEAD(, ktr_request) ktr_free;
@@ -791,6 +795,42 @@ ktrcapfail(type, needed, held)
 	ktr_enqueuerequest(td, req);
 	ktrace_exit(td);
 }
+
+void
+ktrfault(vaddr, type)
+	vm_offset_t vaddr;
+	int type;
+{
+	struct thread *td = curthread;
+	struct ktr_request *req;
+	struct ktr_fault *kf;
+
+	req = ktr_getrequest(KTR_FAULT);
+	if (req == NULL)
+		return;
+	kf = &req->ktr_data.ktr_fault;
+	kf->vaddr = vaddr;
+	kf->type = type;
+	ktr_enqueuerequest(td, req);
+	ktrace_exit(td);
+}
+
+void
+ktrfaultend(result)
+	int result;
+{
+	struct thread *td = curthread;
+	struct ktr_request *req;
+	struct ktr_faultend *kf;
+
+	req = ktr_getrequest(KTR_FAULTEND);
+	if (req == NULL)
+		return;
+	kf = &req->ktr_data.ktr_faultend;
+	kf->result = result;
+	ktr_enqueuerequest(td, req);
+	ktrace_exit(td);
+}
 #endif /* KTRACE */
 
 /* Interface and common routines */
diff --git a/sys/sys/ktrace.h b/sys/sys/ktrace.h
index d537c1b..68008e2 100644
--- a/sys/sys/ktrace.h
+++ b/sys/sys/ktrace.h
@@ -194,6 +194,23 @@ struct ktr_cap_fail {
 };
 
 /*
+ * KTR_FAULT - page fault record
+ */
+#define KTR_FAULT	13
+struct ktr_fault {
+	vm_offset_t vaddr;
+	int type;
+};
+
+/*
+ * KTR_FAULTEND - end of page fault record
+ */
+#define KTR_FAULTEND	14
+struct ktr_faultend {
+	int result;
+};
+
+/*
  * KTR_DROP - If this bit is set in ktr_type, then at least one event
  * between the previous record and this record was dropped.
  */
@@ -215,6 +232,8 @@ struct ktr_cap_fail {
 #define KTRFAC_PROCCTOR	(1<<KTR_PROCCTOR)
 #define KTRFAC_PROCDTOR	(1<<KTR_PROCDTOR)
 #define KTRFAC_CAPFAIL	(1<<KTR_CAPFAIL)
+#define KTRFAC_FAULT	(1<<KTR_FAULT)
+#define KTRFAC_FAULTEND	(1<<KTR_FAULTEND)
 
 /*
  * trace flags (also in p_traceflags)
@@ -227,6 +246,8 @@ struct ktr_cap_fail {
 void	ktrnamei(char *);
 void	ktrcsw(int, int);
 void	ktrpsig(int, sig_t, sigset_t *, int);
+void	ktrfault(vm_offset_t, int);
+void	ktrfaultend(int);
 void	ktrgenio(int, enum uio_rw, struct uio *, int);
 void	ktrsyscall(int, int narg, register_t args[]);
 void	ktrsysctl(int *name, u_int namelen);
diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index 8477c35..b1a0d0c 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -74,6 +74,7 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include "opt_ktrace.h"
 #include "opt_vm.h"
 
 #include <sys/param.h>
@@ -86,6 +87,9 @@ __FBSDID("$FreeBSD$");
 #include <sys/sysctl.h>
 #include <sys/vmmeter.h>
 #include <sys/vnode.h>
+#ifdef KTRACE
+#include <sys/ktrace.h>
+#endif
 
 #include <vm/vm.h>
 #include <vm/vm_param.h>
@@ -208,10 +212,23 @@ int
 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
     int fault_flags)
 {
+	struct thread *td;
+	int result;
 
-	if ((curthread->td_pflags & TDP_NOFAULTING) != 0)
+	td = curthread;
+	if ((td->td_pflags & TDP_NOFAULTING) != 0)
 		return (KERN_PROTECTION_FAILURE);
-	return (vm_fault_hold(map, vaddr, fault_type, fault_flags, NULL));
+#ifdef KTRACE
+	if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
+		ktrfault(vaddr, fault_type);
+#endif
+	result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
+	    NULL);
+#ifdef KTRACE
+	if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
+		ktrfaultend(result);
+#endif
+	return (result);
 }
 
 int