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, 0 insertions, 99 deletions

diff --git a/sys/kern/uipc_syscalls.c b/sys/kern/uipc_syscalls.c
index c9dff02..2d08b7e 100644
--- a/sys/kern/uipc_syscalls.c
+++ b/sys/kern/uipc_syscalls.c
@@ -77,9 +77,6 @@ __FBSDID("$FreeBSD$");
 #include <vm/vm_kern.h>
 #include <vm/vm_extern.h>
 
-static void sf_buf_init(void *arg);
-SYSINIT(sock_sf, SI_SUB_MBUF, SI_ORDER_ANY, sf_buf_init, NULL)
-
 static int sendit(struct thread *td, int s, struct msghdr *mp, int flags);
 static int recvit(struct thread *td, int s, struct msghdr *mp, void *namelenp);
   
@@ -91,17 +88,6 @@ static int getpeername1(struct thread *td, struct getpeername_args *uap,
 			int compat);
 
 /*
- * 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;
-
-/*
  * System call interface to the socket abstraction.
  */
 #if defined(COMPAT_43) || defined(COMPAT_SUNOS)
@@ -1632,91 +1618,6 @@ getsockaddr(namp, uaddr, len)
 }
 
 /*
- * 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);
-}
-
-/*
  * sendfile(2)
  *
  * MPSAFE