Migrate the sf_buf allocator that is used by sendfile(2) and zero-copy

sockets into machine-dependent files.  The rationale for this
migration is illustrated by the modified amd64 allocator.  It uses the
amd64's direct map to avoid emphemeral mappings in the kernel's
address space.  On an SMP, the emphemeral mappings result in an IPI
for TLB shootdown for each transmitted page.  Yuck.

Maintainers of other 64-bit platforms with direct maps should be able
to use the amd64 allocator as a reference implementation.

1 files changed, 104 insertions, 0 deletions

diff --git a/sys/sparc64/sparc64/vm_machdep.c b/sys/sparc64/sparc64/vm_machdep.c
index 983e733..2abca7a 100644
--- a/sys/sparc64/sparc64/vm_machdep.c
+++ b/sys/sparc64/sparc64/vm_machdep.c
@@ -52,7 +52,11 @@
 #include <sys/proc.h>
 #include <sys/bio.h>
 #include <sys/buf.h>
+#include <sys/kernel.h>
 #include <sys/linker_set.h>
+#include <sys/mbuf.h>
+#include <sys/mutex.h>
+#include <sys/socketvar.h>
 #include <sys/sysctl.h>
 #include <sys/unistd.h>
 #include <sys/user.h>
@@ -63,6 +67,7 @@
 #include <vm/vm.h>
 #include <vm/vm_extern.h>
 #include <vm/pmap.h>
+#include <vm/vm_kern.h>
 #include <vm/vm_map.h>
 #include <vm/vm_page.h>
 #include <vm/vm_pageout.h>
@@ -81,6 +86,20 @@
 #include <machine/tlb.h>
 #include <machine/tstate.h>
 
+static void	sf_buf_init(void *arg);
+SYSINIT(sock_sf, SI_SUB_MBUF, SI_ORDER_ANY, sf_buf_init, NULL)
+
+/*
+ * Expanded sf_freelist head. Really an SLIST_HEAD() in disguise, with the
+ * sf_freelist head with the sf_lock mutex.
+ */
+static struct {
+	SLIST_HEAD(, sf_buf) sf_head;
+	struct mtx sf_lock;
+} sf_freelist;
+
+static u_int	sf_buf_alloc_want;
+
 PMAP_STATS_VAR(uma_nsmall_alloc);
 PMAP_STATS_VAR(uma_nsmall_alloc_oc);
 PMAP_STATS_VAR(uma_nsmall_free);
@@ -330,6 +349,91 @@ is_physical_memory(vm_paddr_t addr)
 	return (0);
 }
 
+/*
+ * Allocate a pool of sf_bufs (sendfile(2) or "super-fast" if you prefer. :-))
+ */
+static void
+sf_buf_init(void *arg)
+{
+	struct sf_buf *sf_bufs;
+	vm_offset_t sf_base;
+	int i;
+
+	mtx_init(&sf_freelist.sf_lock, "sf_bufs list lock", NULL, MTX_DEF);
+	mtx_lock(&sf_freelist.sf_lock);
+	SLIST_INIT(&sf_freelist.sf_head);
+	sf_base = kmem_alloc_nofault(kernel_map, nsfbufs * PAGE_SIZE);
+	sf_bufs = malloc(nsfbufs * sizeof(struct sf_buf), M_TEMP,
+	    M_NOWAIT | M_ZERO);
+	for (i = 0; i < nsfbufs; i++) {
+		sf_bufs[i].kva = sf_base + i * PAGE_SIZE;
+		SLIST_INSERT_HEAD(&sf_freelist.sf_head, &sf_bufs[i], free_list);
+	}
+	sf_buf_alloc_want = 0;
+	mtx_unlock(&sf_freelist.sf_lock);
+}
+
+/*
+ * Get an sf_buf from the freelist. Will block if none are available.
+ */
+struct sf_buf *
+sf_buf_alloc(struct vm_page *m)
+{
+	struct sf_buf *sf;
+	int error;
+
+	mtx_lock(&sf_freelist.sf_lock);
+	while ((sf = SLIST_FIRST(&sf_freelist.sf_head)) == NULL) {
+		sf_buf_alloc_want++;
+		error = msleep(&sf_freelist, &sf_freelist.sf_lock, PVM|PCATCH,
+		    "sfbufa", 0);
+		sf_buf_alloc_want--;
+
+		/*
+		 * If we got a signal, don't risk going back to sleep. 
+		 */
+		if (error)
+			break;
+	}
+	if (sf != NULL) {
+		SLIST_REMOVE_HEAD(&sf_freelist.sf_head, free_list);
+		sf->m = m;
+		pmap_qenter(sf->kva, &sf->m, 1);
+	}
+	mtx_unlock(&sf_freelist.sf_lock);
+	return (sf);
+}
+
+/*
+ * Detatch mapped page and release resources back to the system.
+ */
+void
+sf_buf_free(void *addr, void *args)
+{
+	struct sf_buf *sf;
+	struct vm_page *m;
+
+	sf = args;
+	pmap_qremove((vm_offset_t)addr, 1);
+	m = sf->m;
+	vm_page_lock_queues();
+	vm_page_unwire(m, 0);
+	/*
+	 * Check for the object going away on us. This can
+	 * happen since we don't hold a reference to it.
+	 * If so, we're responsible for freeing the page.
+	 */
+	if (m->wire_count == 0 && m->object == NULL)
+		vm_page_free(m);
+	vm_page_unlock_queues();
+	sf->m = NULL;
+	mtx_lock(&sf_freelist.sf_lock);
+	SLIST_INSERT_HEAD(&sf_freelist.sf_head, sf, free_list);
+	if (sf_buf_alloc_want > 0)
+		wakeup_one(&sf_freelist);
+	mtx_unlock(&sf_freelist.sf_lock);
+}
+
 void
 swi_vm(void *v)
 {