diff --git a/share/man/man5/core.5 b/share/man/man5/core.5
--- a/share/man/man5/core.5
+++ b/share/man/man5/core.5
@@ -28,7 +28,7 @@
 .\"     @(#)core.5	8.3 (Berkeley) 12/11/93
 .\" $FreeBSD$
 .\"
-.Dd August 2, 2020
+.Dd October 5, 2021
 .Dt CORE 5
 .Os
 .Sh NAME
@@ -52,9 +52,21 @@
 .Xr savecore 8 . )
 .Pp
 The maximum size of a core file is limited by
-.Xr setrlimit 2 .
+.Xr setrlimit 2 limit
+.Dv RLIMIT_CORE .
 Files which would be larger than the limit are not created.
 .Pp
+With the limit large enough, processes that mapped a very large,
+and perhaps sparcely populated, virtual memory regions, could take
+a very long time to create core dumps.
+Signals cannot interrupt the write of the core dump, except
+.Dv SIGKILL .
+The later behavior can be disabled by setting
+.Xr sysctl 8
+variable
+.Va kern.core_dump_intr
+to zero.
+.Pp
 The name of the file is controlled via the
 .Xr sysctl 8
 variable
diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -151,6 +151,11 @@
 SYSCTL_INT(_security_bsd, OID_AUTO, map_at_zero, CTLFLAG_RWTUN, &map_at_zero, 0,
     "Permit processes to map an object at virtual address 0.");
 
+static int core_dump_intr = 1;
+SYSCTL_INT(_kern, OID_AUTO, core_dump_intr, CTLFLAG_RW,
+    &core_dump_intr, 0,
+    "Core dumping interruptible with SIGKILL");
+
 static int
 sysctl_kern_ps_strings(SYSCTL_HANDLER_ARGS)
 {
@@ -1926,7 +1931,7 @@
 	struct mount *mp;
 	size_t resid, runlen;
 	int error;
-	bool success;
+	bool interrupted, success;
 
 	KASSERT((uintptr_t)base % PAGE_SIZE == 0,
 	    ("%s: user address %p is not page-aligned", __func__, base));
@@ -1935,7 +1940,8 @@
 		return (compress_chunk(cp, base, tmpbuf, len));
 
 	map = &cp->td->td_proc->p_vmspace->vm_map;
-	for (; len > 0; base += runlen, offset += runlen, len -= runlen) {
+	for (interrupted = false; len > 0;
+	    base += runlen, offset += runlen, len -= runlen) {
 		/*
 		 * Attempt to page in all virtual pages in the range.  If a
 		 * virtual page is not backed by the pager, it is represented as
@@ -1943,6 +1949,12 @@
 		 * anonymous memory or truncated files, for example.
 		 */
 		for (runlen = 0; runlen < len; runlen += PAGE_SIZE) {
+			if (core_dump_intr && curproc_is_killed_9()) {
+				error = EINTR;
+				success = false;
+				interrupted = true;
+				break;
+			}
 			error = vm_fault(map, (uintptr_t)base + runlen,
 			    VM_PROT_READ, VM_FAULT_NOFILL, NULL);
 			if (runlen == 0)
@@ -1951,6 +1963,8 @@
 				break;
 		}
 
+		if (interrupted)
+			break;
 		if (success) {
 			error = core_write(cp, base, runlen, offset,
 			    UIO_USERSPACE, &resid);
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -214,7 +214,6 @@
 #define	SIGPROP_TTYSTOP		0x08	/* ditto, from tty */
 #define	SIGPROP_IGNORE		0x10	/* ignore by default */
 #define	SIGPROP_CONT		0x20	/* continue if suspended */
-#define	SIGPROP_CANTMASK	0x40	/* non-maskable, catchable */
 
 static int sigproptbl[NSIG] = {
 	[SIGHUP] =	SIGPROP_KILL,
@@ -3277,6 +3276,29 @@
 	return (ret);
 }
 
+bool
+curproc_is_killed_9(void)
+{
+	struct thread *td;
+	struct proc *p;
+	struct sigacts *ps;
+	bool res;
+
+	td = curthread;
+	if ((td->td_flags & TDF_NEEDSIGCHK) == 0)
+		return (false);
+
+	p = td->td_proc;
+	PROC_LOCK(p);
+	ps = p->p_sigacts;
+	mtx_lock(&ps->ps_mtx);
+	res = SIGISMEMBER(td->td_sigqueue.sq_signals, SIGKILL) ||
+	    SIGISMEMBER(p->p_sigqueue.sq_signals, SIGKILL);
+	mtx_unlock(&ps->ps_mtx);
+	PROC_UNLOCK(p);
+	return (res);
+}
+
 void
 proc_wkilled(struct proc *p)
 {
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -1162,7 +1162,7 @@
 extern	void (*cpu_idle_hook)(sbintime_t);	/* Hook to machdep CPU idler. */
 void	cpu_switch(struct thread *, struct thread *, struct mtx *);
 void	cpu_throw(struct thread *, struct thread *) __dead2;
-void	unsleep(struct thread *);
+bool	curproc_is_killed_9(void);
 void	userret(struct thread *, struct trapframe *);
 
 void	cpu_exit(struct thread *);