sys/vm: Add TSLOG to some functions

The functions pbuf_init, kva_alloc, and keg_alloc_slab are significant
contributors to the kernel boot time when FreeBSD boots inside the
Firecracker VMM.  Instrument them so they show up on flamecharts.

sys/vm/uma_core.c

@@ -1762,6 +1762,8 @@ keg_alloc_slab(uma_keg_t keg, uma_zone_t zone, int domain, int flags,
 	uint8_t sflags;
 	int i;
 
+	TSENTER();
+
 	KASSERT(domain >= 0 && domain < vm_ndomains,
 	    ("keg_alloc_slab: domain %d out of range", domain));
 
@@ -1858,6 +1860,7 @@ keg_alloc_slab(uma_keg_t keg, uma_zone_t zone, int domain, int flags,
 	dom->ud_pages += keg->uk_ppera;
 	dom->ud_free_items += keg->uk_ipers;
 
+	TSEXIT();
 	return (slab);
 
 fail:

sys/vm/vm_kern.c

@@ -148,9 +148,11 @@ kva_alloc(vm_size_t size)
 {
 	vm_offset_t addr;
 
+	TSENTER();
 	size = round_page(size);
 	if (vmem_alloc(kernel_arena, size, M_BESTFIT | M_NOWAIT, &addr))
 		return (0);
+	TSEXIT();
 
 	return (addr);
 }

sys/vm/vm_pager.c

@@ -495,6 +495,8 @@ pbuf_init(void *mem, int size, int flags)
 {
 	struct buf *bp = mem;
 
+	TSENTER();
+
 	bp->b_kvabase = (void *)kva_alloc(ptoa(PBUF_PAGES));
 	if (bp->b_kvabase == NULL)
 		return (ENOMEM);
@@ -504,6 +506,8 @@ pbuf_init(void *mem, int size, int flags)
 	bp->b_rcred = bp->b_wcred = NOCRED;
 	bp->b_xflags = 0;
 
+	TSEXIT();
+
 	return (0);
 }