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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.
This commit is contained in:
rmind 2009-10-05 23:47:04 +00:00
parent c3a98b4c87
commit 5503429772
1 changed files with 29 additions and 42 deletions
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71
sys/kern/sysv_shm.c
View File

@ -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 @@ shmexit(struct vmspace *vm)
{
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 @@ shmexit(struct vmspace *vm)
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));
}