Module Name: src
Committed By: rmind
Date: Mon Oct 5 23:47:04 UTC 2009
Modified Files:
src/sys/kern: sysv_shm.c
Log Message:
shmexit: simplify a lot by avoiding unnecessary memory allocations, since
it is a last reference, just re-lock and check mapping list again. Often
there wont be re-locks at all, moreover, shm_lock is not contended at all.
To generate a diff of this commit:
cvs rdiff -u -r1.116 -r1.117 src/sys/kern/sysv_shm.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/sysv_shm.c
diff -u src/sys/kern/sysv_shm.c:1.116 src/sys/kern/sysv_shm.c:1.117
--- src/sys/kern/sysv_shm.c:1.116 Fri Mar 6 20:31:54 2009
+++ src/sys/kern/sysv_shm.c Mon Oct 5 23:47:04 2009
@@ -1,4 +1,4 @@
-/* $NetBSD: sysv_shm.c,v 1.116 2009/03/06 20:31:54 joerg Exp $ */
+/* $NetBSD: sysv_shm.c,v 1.117 2009/10/05 23:47:04 rmind Exp $ */
/*-
* Copyright (c) 1999, 2007 The NetBSD Foundation, Inc.
@@ -61,7 +61,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sysv_shm.c,v 1.116 2009/03/06 20:31:54 joerg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sysv_shm.c,v 1.117 2009/10/05 23:47:04 rmind Exp $");
#define SYSVSHM
@@ -800,11 +800,6 @@
{
struct shmmap_state *shmmap_s;
struct shmmap_entry *shmmap_se;
- struct uvm_object **uobj;
- size_t *size;
- u_int i, n;
-
- SLIST_HEAD(, shmmap_entry) tmp_entries;
mutex_enter(&shm_lock);
shmmap_s = (struct shmmap_state *)vm->vm_shm;
@@ -812,62 +807,54 @@
mutex_exit(&shm_lock);
return;
}
-
vm->vm_shm = NULL;
if (--shmmap_s->nrefs > 0) {
SHMPRINTF(("shmexit: vm %p drop ref (%d entries), refs = %d\n",
vm, shmmap_s->nitems, shmmap_s->nrefs));
- SLIST_FOREACH(shmmap_se, &shmmap_s->entries, next)
+ SLIST_FOREACH(shmmap_se, &shmmap_s->entries, next) {
shmsegs[IPCID_TO_IX(shmmap_se->shmid)].shm_nattch--;
+ }
mutex_exit(&shm_lock);
return;
}
- KASSERT(shmmap_s->nrefs == 0);
- n = shmmap_s->nitems;
- SHMPRINTF(("shmexit: vm %p cleanup (%d entries)\n", vm, n));
- mutex_exit(&shm_lock);
- if (n == 0) {
+ SHMPRINTF(("shmexit: vm %p cleanup (%d entries)\n", vm, shmmap_s->nitems));
+ if (shmmap_s->nitems == 0) {
+ mutex_exit(&shm_lock);
kmem_free(shmmap_s, sizeof(struct shmmap_state));
return;
}
- /* Allocate the arrays */
- SLIST_INIT(&tmp_entries);
- uobj = kmem_zalloc(n * sizeof(void *), KM_SLEEP);
- size = kmem_zalloc(n * sizeof(size_t), KM_SLEEP);
-
- /* Delete the entry from shm map */
- i = 0;
- mutex_enter(&shm_lock);
- while (!SLIST_EMPTY(&shmmap_s->entries)) {
+ /*
+ * Delete the entry from shm map.
+ */
+ for (;;) {
struct shmid_ds *shmseg;
+ struct uvm_object *uobj;
+ size_t sz;
shmmap_se = SLIST_FIRST(&shmmap_s->entries);
+ KASSERT(shmmap_se != NULL);
+
shmseg = &shmsegs[IPCID_TO_IX(shmmap_se->shmid)];
- size[i] = (shmseg->shm_segsz + PGOFSET) & ~PGOFSET;
- uobj[i] = shm_delete_mapping(shmmap_s, shmmap_se);
- SLIST_INSERT_HEAD(&tmp_entries, shmmap_se, next);
- i++;
- }
- mutex_exit(&shm_lock);
+ sz = (shmseg->shm_segsz + PGOFSET) & ~PGOFSET;
+ /* shm_delete_mapping() removes from the list. */
+ uobj = shm_delete_mapping(shmmap_s, shmmap_se);
+ mutex_exit(&shm_lock);
- /* Unmap all segments, free the entries */
- i = 0;
- while (!SLIST_EMPTY(&tmp_entries)) {
- KASSERT(i < n);
- shmmap_se = SLIST_FIRST(&tmp_entries);
- SLIST_REMOVE(&tmp_entries, shmmap_se, shmmap_entry, next);
- uvm_deallocate(&vm->vm_map, shmmap_se->va, size[i]);
- if (uobj[i] != NULL)
- uao_detach(uobj[i]);
+ uvm_deallocate(&vm->vm_map, shmmap_se->va, sz);
+ if (uobj != NULL) {
+ uao_detach(uobj);
+ }
pool_put(&shmmap_entry_pool, shmmap_se);
- i++;
- }
- kmem_free(uobj, n * sizeof(void *));
- kmem_free(size, n * sizeof(size_t));
+ if (SLIST_EMPTY(&shmmap_s->entries)) {
+ break;
+ }
+ mutex_enter(&shm_lock);
+ KASSERT(!SLIST_EMPTY(&shmmap_s->entries));
+ }
kmem_free(shmmap_s, sizeof(struct shmmap_state));
}
