mach-defpager: replace the magic typecast with a hash table

Previously, the mach-defpager used a "magic typecast" for object
lookups.  It renamed the port to the address of the associated object,
and upon receiving a message it would cast the port name back to a
pointer.

While this might seem like an optimization, it actually makes the port
handling in the kernel less efficient.  Ports with small continuous
names are stored in an array, while other ports get spilled in a splay
tree.

Replace the linked list of default_port_t objects with a hash table.
Do not rename the ports, rather use the hash table to lookup objects
associated with ports.

* mach-defpager/default_pager.c (struct pager_port): Replace queue
with hash table, remove count, move type declaration to priv.h.
(pager_port_list_init): Adjust accordingly.
(pager_port_list_insert): Likewise.
(pager_port_list_delete): Likewise.
(destroy_paging_partition): Replace queue_iterate with HURD_IHASH_ITERATE.
(S_default_pager_objects): Likewise.
(S_default_pager_object_pages): Likewise.
(seqnos_memory_object_create): Do not rename the port but store it in
the hash table.
(S_default_pager_object_create): Likewise.
* mach-defpager/priv.h (struct dstruct): Add fast-removal pointer.
(pnameof): Remove obsolete macro definition.
(dnameof): Likewise.
* mach-defpager/mig-decls.h (begin_using_default_pager): Replace the
magic typecast with a hash table lookup.
* mach-defpager/Makefile (HURDLIBS): Add ihash.

1 files changed, 26 insertions, 58 deletions

diff --git a/mach-defpager/default_pager.c b/mach-defpager/default_pager.c
index eb444a6b..f514ea6b 100644
--- a/mach-defpager/default_pager.c
+++ b/mach-defpager/default_pager.c
@@ -38,10 +38,13 @@
 #include <mach/default_pager_types.h>
 
 #include <pthread.h>
+#include <stddef.h>
 
 #include <device/device_types.h>
 #include <device/device.h>
 
+#include <hurd/ihash.h>
+
 #include "queue.h"
 #include "wiring.h"
 #include "kalloc.h"
@@ -1781,25 +1784,14 @@ default_has_page(ds, offset)
 #define	dstruct_unlock(ds)
 #endif	/* PARALLEL */
 
-/*
- * List of all pagers.  A specific pager is
- * found directly via its port, this list is
- * only used for monitoring purposes by the
- * default_pager_object* calls
- */
-struct pager_port {
-	queue_head_t	queue;
-	pthread_mutex_t	lock;
-	int		count;	/* saves code */
-	queue_head_t	leak_queue;
-} all_pagers;
+struct pager_port all_pagers;
 
 #define pager_port_list_init()					\
 {								\
 	pthread_mutex_init(&all_pagers.lock, NULL);		\
-	queue_init(&all_pagers.queue);				\
+	hurd_ihash_init (&all_pagers.htable,			\
+			 offsetof (struct dstruct, htable_locp)); \
 	queue_init(&all_pagers.leak_queue);			\
-	all_pagers.count = 0;					\
 }
 
 void pager_port_list_insert(port, ds)
@@ -1807,8 +1799,9 @@ void pager_port_list_insert(port, ds)
 	default_pager_t	ds;
 {
 	pthread_mutex_lock(&all_pagers.lock);
-	queue_enter(&all_pagers.queue, ds, default_pager_t, links);
-	all_pagers.count++;
+	hurd_ihash_add (&all_pagers.htable,
+			(hurd_ihash_key_t) port,
+			(hurd_ihash_value_t) ds);
 	pthread_mutex_unlock(&all_pagers.lock);
 }
 
@@ -1816,8 +1809,8 @@ void pager_port_list_delete(ds)
 	default_pager_t ds;
 {
 	pthread_mutex_lock(&all_pagers.lock);
-	queue_remove(&all_pagers.queue, ds, default_pager_t, links);
-	all_pagers.count--;
+	hurd_ihash_locp_remove (&all_pagers.htable,
+				ds->htable_locp);
 	pthread_mutex_unlock(&all_pagers.lock);
 }
 
@@ -1864,7 +1857,8 @@ dprintf("Partition x%x (id x%x) for %s, all_ok %d\n", part, id, name, all_ok);
 	pthread_mutex_lock(&part->p_lock);
 
 	pthread_mutex_lock(&all_pagers.lock);
-	queue_iterate(&all_pagers.queue, entry, default_pager_t, links) {
+	HURD_IHASH_ITERATE (&all_pagers.htable, val) {
+		entry = (default_pager_t) val;
 
 		dstruct_lock(entry);
 
@@ -2238,7 +2232,6 @@ seqnos_memory_object_create(old_pager, seqno, new_pager, new_size,
 	vm_size_t	new_page_size;
 {
 	default_pager_t	ds;
-	kern_return_t			kr;
 
 	assert(old_pager == default_pager_default_port);
 	assert(MACH_PORT_VALID(new_pager_request));
@@ -2246,24 +2239,6 @@ seqnos_memory_object_create(old_pager, seqno, new_pager, new_size,
 	assert(new_page_size == vm_page_size);
 
 	ds = pager_port_alloc(new_size);
-rename_it:
-	kr = mach_port_rename(	default_pager_self,
-				new_pager, (mach_port_t)pnameof(ds));
-	if (kr != KERN_SUCCESS) {
-		default_pager_t	ds1;
-
-		if (kr != KERN_NAME_EXISTS)
-			panic("%s m_o_create", my_name);
-		ds1 = (default_pager_t) kalloc(sizeof *ds1);
-		*ds1 = *ds;
-		pthread_mutex_lock(&all_pagers.lock);
-		queue_enter(&all_pagers.leak_queue, ds, default_pager_t, links);
-		pthread_mutex_unlock(&all_pagers.lock);
-		ds = ds1;
-		goto rename_it;
-	}
-
-	new_pager = (mach_port_t) pnameof(ds);
 
 	/*
 	 *	Set up associations between these ports
@@ -3195,23 +3170,14 @@ S_default_pager_object_create (mach_port_t pager,
 		return KERN_INVALID_ARGUMENT;
 
 	ds = pager_port_alloc(size);
-rename_it:
-	port = (mach_port_t) pnameof(ds);
-	result = mach_port_allocate_name(default_pager_self,
-				    MACH_PORT_RIGHT_RECEIVE, port);
-	if (result != KERN_SUCCESS) {
-		default_pager_t	ds1;
-
-		if (result != KERN_NAME_EXISTS) return (result);
-
-		ds1 = (default_pager_t) kalloc(sizeof *ds1);
-		*ds1 = *ds;
-		pthread_mutex_lock(&all_pagers.lock);
-		queue_enter(&all_pagers.leak_queue, ds, default_pager_t, links);
-		pthread_mutex_unlock(&all_pagers.lock);
-		ds = ds1;
-		goto rename_it;
-	}
+	result = mach_port_allocate (default_pager_self,
+				     MACH_PORT_RIGHT_RECEIVE,
+				     &port);
+	if (result != KERN_SUCCESS)
+	  {
+	    kfree ((char *) ds, sizeof *ds);
+	    return result;
+	  }
 
 	/*
 	 *	Set up associations between these ports
@@ -3285,7 +3251,7 @@ S_default_pager_objects (mach_port_t pager,
 	/*
 	 * We will send no more than this many
 	 */
-	actual = all_pagers.count;
+	actual = all_pagers.htable.nr_items;
 	pthread_mutex_unlock(&all_pagers.lock);
 
 	if (opotential < actual) {
@@ -3327,7 +3293,8 @@ S_default_pager_objects (mach_port_t pager,
 	pthread_mutex_lock(&all_pagers.lock);
 
 	num_pagers = 0;
-	queue_iterate(&all_pagers.queue, entry, default_pager_t, links) {
+	HURD_IHASH_ITERATE (&all_pagers.htable, val) {
+		entry = (default_pager_t) val;
 
 		mach_port_t		port;
 		vm_size_t		size;
@@ -3505,7 +3472,8 @@ S_default_pager_object_pages (mach_port_t pager,
 		default_pager_t		entry;
 
 		pthread_mutex_lock(&all_pagers.lock);
-		queue_iterate(&all_pagers.queue, entry, default_pager_t, links) {
+		HURD_IHASH_ITERATE (&all_pagers.htable, val) {
+			entry = (default_pager_t) val;
 			dstruct_lock(entry);
 			if (entry->pager_name == object) {
 				pthread_mutex_unlock(&all_pagers.lock);