MFamd64

 Simplify the sf_buf implementation.  In short, make it a veneer
 over the direct virtual-to-physical mapping.

2 files changed, 16 insertions, 74 deletions

diff --git a/sys/alpha/alpha/vm_machdep.c b/sys/alpha/alpha/vm_machdep.c
index 25cf80e..5fa5c7f 100644
--- a/sys/alpha/alpha/vm_machdep.c
+++ b/sys/alpha/alpha/vm_machdep.c
@@ -101,20 +101,6 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/user.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;
-
 /*
  * Finish a fork operation, with process p2 nearly set up.
  * Copy and update the pcb, set up the stack so that the child
@@ -384,69 +370,24 @@ cpu_reset()
 }
 
 /*
- * 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;
-	int i;
-
-	mtx_init(&sf_freelist.sf_lock, "sf_bufs list lock", NULL, MTX_DEF);
-	SLIST_INIT(&sf_freelist.sf_head);
-	sf_bufs = malloc(nsfbufs * sizeof(struct sf_buf), M_TEMP,
-	    M_NOWAIT | M_ZERO);
-	for (i = 0; i < nsfbufs; i++)
-		SLIST_INSERT_HEAD(&sf_freelist.sf_head, &sf_bufs[i], free_list);
-	sf_buf_alloc_want = 0;
-}
-
-/*
- * Get an sf_buf from the freelist. Will block if none are available.
+ * Allocate an sf_buf for the given vm_page.  On this machine, however, there
+ * is no sf_buf object.  Instead, an opaque pointer to the given vm_page is
+ * returned.
  */
 struct sf_buf *
 sf_buf_alloc(struct vm_page *m, int pri)
 {
-	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++;
-		mbstat.sf_allocwait++;
-		error = msleep(&sf_freelist, &sf_freelist.sf_lock, PVM | pri,
-		    "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;
-		nsfbufsused++;
-		nsfbufspeak = imax(nsfbufspeak, nsfbufsused);
-	}
-	mtx_unlock(&sf_freelist.sf_lock);
-	return (sf);
+
+	return ((struct sf_buf *)m);
 }
 
 /*
- * Release resources back to the system.
+ * Free the sf_buf.  In fact, do nothing because there are no resources
+ * associated with the sf_buf.
  */
 void
 sf_buf_free(struct sf_buf *sf)
 {
-
-	mtx_lock(&sf_freelist.sf_lock);
-	SLIST_INSERT_HEAD(&sf_freelist.sf_head, sf, free_list);
-	nsfbufsused--;
-	if (sf_buf_alloc_want > 0)
-		wakeup_one(&sf_freelist);
-	mtx_unlock(&sf_freelist.sf_lock);
 }
 
 /*
diff --git a/sys/alpha/include/sf_buf.h b/sys/alpha/include/sf_buf.h
index 8c7d7a6..d000e30 100644
--- a/sys/alpha/include/sf_buf.h
+++ b/sys/alpha/include/sf_buf.h
@@ -29,29 +29,30 @@
 #ifndef _MACHINE_SF_BUF_H_
 #define _MACHINE_SF_BUF_H_
 
-#include <sys/queue.h>
-
 #include <vm/vm.h>
 #include <vm/vm_param.h>
 #include <vm/vm_page.h>
 
-struct sf_buf {
-	SLIST_ENTRY(sf_buf) free_list;	/* list of free buffer slots */
-	vm_page_t m;			/* currently mapped page */
-};
+/*
+ * On this machine, the only purpose for which sf_buf is used is to implement
+ * an opaque pointer required by the machine-independent parts of the kernel.
+ * That pointer references the vm_page that is "mapped" by the sf_buf.  The
+ * actual mapping is provided by the direct virtual-to-physical mapping.  
+ */
+struct sf_buf;
 
 static __inline vm_offset_t
 sf_buf_kva(struct sf_buf *sf)
 {
 
-	return (ALPHA_PHYS_TO_K0SEG(sf->m->phys_addr));
+	return (ALPHA_PHYS_TO_K0SEG(VM_PAGE_TO_PHYS((vm_page_t)sf)));
 }
 
 static __inline vm_page_t
 sf_buf_page(struct sf_buf *sf)
 {
 
-	return (sf->m);
+	return ((vm_page_t)sf);
 }
 
 #endif /* !_MACHINE_SF_BUF_H_ */