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Implement kern.maxvnodes. adjusting kern.maxvnodes now actually has a

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real effect.

Optimize vfs_msync().  Avoid having to continually drop and re-obtain
mutexes when scanning the vnode list.  Improves looping case by 500%.

Optimize ffs_sync().  Avoid having to continually drop and re-obtain
mutexes when scanning the vnode list.  This makes a couple of assumptions,
which I believe are ok, in regards to vnode stability when the mount list
mutex is held.  Improves looping case by 500%.

(more optimization work is needed on top of these fixes)

MFC after:	1 week
This commit is contained in:
Matthew Dillon 2001-10-26 00:08:05 +00:00
parent 5a5f6965ba
commit 245df27cee
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=85517
7 changed files with 145 additions and 57 deletions
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112
sys/kern/vfs_subr.c
View File

@ -518,6 +518,49 @@ vattr_null(vap)
vap->va_vaflags = 0;
}
/*
* This routine is called when we have too many vnodes. It attempts
* to free <count> vnodes and will potentially free vnodes that still
* have VM backing store (VM backing store is typically the cause
* of a vnode blowout so we want to do this). Therefore, this operation
* is not considered cheap.
*
* A number of conditions may prevent a vnode from being reclaimed.
* the buffer cache may have references on the vnode, a directory
* vnode may still have references due to the namei cache representing
* underlying files, or the vnode may be in active use. It is not
* desireable to reuse such vnodes. These conditions may cause the
* number of vnodes to reach some minimum value regardless of what
* you set kern.maxvnodes to. Do not set kernl.maxvnodes too low.
*/
static void
vlrureclaim(struct mount *mp, int count)
{
struct vnode *vp;
mtx_lock(&mntvnode_mtx);
while (count && (vp = TAILQ_FIRST(&mp->mnt_nvnodelist)) != NULL) {
TAILQ_REMOVE(&mp->mnt_nvnodelist, vp, v_nmntvnodes);
TAILQ_INSERT_TAIL(&mp->mnt_nvnodelist, vp, v_nmntvnodes);
if (vp->v_type != VNON &&
vp->v_type != VBAD &&
VMIGHTFREE(vp) && /* critical path opt */
mtx_trylock(&vp->v_interlock)
) {
mtx_unlock(&mntvnode_mtx);
if (VMIGHTFREE(vp)) {
vgonel(vp, curthread);
} else {
mtx_unlock(&vp->v_interlock);
}
mtx_lock(&mntvnode_mtx);
}
--count;
}
mtx_unlock(&mntvnode_mtx);
}
/*
* Routines having to do with the management of the vnode table.
*/
@ -532,25 +575,33 @@ getnewvnode(tag, mp, vops, vpp)
vop_t **vops;
struct vnode **vpp;
{
int s, count;
int s;
struct thread *td = curthread; /* XXX */
struct vnode *vp = NULL;
struct mount *vnmp;
vm_object_t object;
s = splbio();
/*
* We take the least recently used vnode from the freelist
* if we can get it and it has no cached pages, and no
* namecache entries are relative to it.
* Otherwise we allocate a new vnode
* Try to reuse vnodes if we hit the max. This situation only
* occurs in certain large-memory (2G+) situations. For the
* algorithm to be stable we have to try to reuse at least 2.
* No hysteresis should be necessary.
*/
if (numvnodes - freevnodes > desiredvnodes)
vlrureclaim(mp, 2);
/*
* Attempt to reuse a vnode already on the free list, allocating
* a new vnode if we can't find one or if we have not reached a
* good minimum for good LRU performance.
*/
s = splbio();
mtx_lock(&vnode_free_list_mtx);
if (freevnodes < wantfreevnodes) {
vp = NULL;
} else if (numvnodes >= minvnodes) {
if (freevnodes >= wantfreevnodes && numvnodes >= minvnodes) {
int count;
for (count = 0; count < freevnodes; count++) {
vp = TAILQ_FIRST(&vnode_free_list);
if (vp == NULL || vp->v_usecount)
@ -2408,22 +2459,20 @@ vfs_msync(struct mount *mp, int flags)
{
struct vnode *vp, *nvp;
struct vm_object *obj;
int anyio, tries;
int tries;
GIANT_REQUIRED;
tries = 5;
loop:
anyio = 0;
mtx_lock(&mntvnode_mtx);
loop:
for (vp = TAILQ_FIRST(&mp->mnt_nvnodelist); vp != NULL; vp = nvp) {
nvp = TAILQ_NEXT(vp, v_nmntvnodes);
if (vp->v_mount != mp) {
mtx_unlock(&mntvnode_mtx);
goto loop;
if (--tries > 0)
goto loop;
break;
}
nvp = TAILQ_NEXT(vp, v_nmntvnodes);
if (vp->v_flag & VXLOCK) /* XXX: what if MNT_WAIT? */
continue;
@ -2431,36 +2480,27 @@ vfs_msync(struct mount *mp, int flags)
if (vp->v_flag & VNOSYNC) /* unlinked, skip it */
continue;
if (flags != MNT_WAIT) {
if (VOP_GETVOBJECT(vp, &obj) != 0 ||
(obj->flags & OBJ_MIGHTBEDIRTY) == 0)
continue;
if (VOP_ISLOCKED(vp, NULL))
continue;
}
mtx_unlock(&mntvnode_mtx);
mtx_lock(&vp->v_interlock);
if (VOP_GETVOBJECT(vp, &obj) == 0 &&
(obj->flags & OBJ_MIGHTBEDIRTY)) {
if ((vp->v_flag & VOBJDIRTY) &&
(flags == MNT_WAIT || VOP_ISLOCKED(vp, NULL) == 0)) {
mtx_unlock(&mntvnode_mtx);
if (!vget(vp,
LK_INTERLOCK | LK_EXCLUSIVE | LK_RETRY | LK_NOOBJ, curthread)) {
LK_EXCLUSIVE | LK_RETRY | LK_NOOBJ, curthread)) {
if (VOP_GETVOBJECT(vp, &obj) == 0) {
vm_object_page_clean(obj, 0, 0,
flags == MNT_WAIT ?
OBJPC_SYNC : OBJPC_NOSYNC);
anyio = 1;
}
vput(vp);
}
} else {
mtx_unlock(&vp->v_interlock);
mtx_lock(&mntvnode_mtx);
if (TAILQ_NEXT(vp, v_nmntvnodes) != nvp) {
if (--tries > 0)
goto loop;
break;
}
}
mtx_lock(&mntvnode_mtx);
}
mtx_unlock(&mntvnode_mtx);
if (anyio && (--tries > 0))
goto loop;
}
/*

5
sys/sys/vnode.h
View File

@ -175,6 +175,7 @@ struct vnode {
/* open for business 0x100000 */
#define VONWORKLST 0x200000 /* On syncer work-list */
#define VMOUNT 0x400000 /* Mount in progress */
#define VOBJDIRTY 0x800000 /* object might be dirty */
/*
* Vnode attributes. A field value of VNOVAL represents a field whose value
@ -311,6 +312,10 @@ extern void (*lease_updatetime) __P((int deltat));
(!(vp)->v_object || \
!((vp)->v_object->ref_count || (vp)->v_object->resident_page_count)))
#define VMIGHTFREE(vp) \
(!((vp)->v_flag & (VFREE|VDOOMED)) && \
!(vp)->v_holdcnt && !(vp)->v_usecount)
#define VSHOULDBUSY(vp) \
(((vp)->v_flag & VFREE) && \
((vp)->v_holdcnt || (vp)->v_usecount))

38
sys/ufs/ffs/ffs_vfsops.c
View File

@ -1001,10 +1001,10 @@ ffs_sync(mp, waitfor, cred, td)
* Write back each (modified) inode.
*/
wait = 0;
lockreq = LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK;
lockreq = LK_EXCLUSIVE | LK_NOWAIT;
if (waitfor == MNT_WAIT) {
wait = 1;
lockreq = LK_EXCLUSIVE | LK_INTERLOCK;
lockreq = LK_EXCLUSIVE;
}
mtx_lock(&mntvnode_mtx);
loop:
@ -1015,34 +1015,40 @@ ffs_sync(mp, waitfor, cred, td)
*/
if (vp->v_mount != mp)
goto loop;
nvp = TAILQ_NEXT(vp, v_nmntvnodes);
mtx_unlock(&mntvnode_mtx);
mtx_lock(&vp->v_interlock);
/*
* Depend on the mntvnode_slock to keep things stable enough
* for a quick test. Since there might be hundreds of
* thousands of vnodes, we cannot afford even a subroutine
* call unless there's a good chance that we have work to do.
*/
nvp = TAILQ_NEXT(vp, v_nmntvnodes);
ip = VTOI(vp);
if (vp->v_type == VNON || ((ip->i_flag &
(IN_ACCESS | IN_CHANGE | IN_MODIFIED | IN_UPDATE)) == 0 &&
TAILQ_EMPTY(&vp->v_dirtyblkhd))) {
mtx_unlock(&vp->v_interlock);
mtx_lock(&mntvnode_mtx);
(IN_ACCESS | IN_CHANGE | IN_MODIFIED | IN_UPDATE)) == 0 &&
TAILQ_EMPTY(&vp->v_dirtyblkhd))) {
continue;
}
if (vp->v_type != VCHR) {
mtx_unlock(&mntvnode_mtx);
if ((error = vget(vp, lockreq, td)) != 0) {
mtx_lock(&mntvnode_mtx);
if (error == ENOENT)
goto loop;
continue;
} else {
if ((error = VOP_FSYNC(vp, cred, waitfor, td)) != 0)
allerror = error;
VOP_UNLOCK(vp, 0, td);
vrele(vp);
mtx_lock(&mntvnode_mtx);
}
if ((error = VOP_FSYNC(vp, cred, waitfor, td)) != 0)
allerror = error;
VOP_UNLOCK(vp, 0, td);
vrele(vp);
} else {
mtx_unlock(&vp->v_interlock);
mtx_unlock(&mntvnode_mtx);
UFS_UPDATE(vp, wait);
mtx_lock(&mntvnode_mtx);
}
mtx_lock(&mntvnode_mtx);
if (TAILQ_NEXT(vp, v_nmntvnodes) != nvp)
goto loop;
}
mtx_unlock(&mntvnode_mtx);
/*

3
sys/vm/vm_fault.c
View File

@ -806,8 +806,7 @@ RetryFault:;
if (prot & VM_PROT_WRITE) {
vm_page_flag_set(fs.m, PG_WRITEABLE);
vm_object_set_flag(fs.m->object,
OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
vm_object_set_writeable_dirty(fs.m->object);
/*
* If the fault is a write, we know that this page is being

41
sys/vm/vm_object.c
View File

@ -321,8 +321,11 @@ vm_object_reference(vm_object_t object)
if (object == NULL)
return;
#if 0
/* object can be re-referenced during final cleaning */
KASSERT(!(object->flags & OBJ_DEAD),
("vm_object_reference: attempting to reference dead obj"));
#endif
object->ref_count++;
if (object->type == OBJT_VNODE) {
@ -454,8 +457,13 @@ vm_object_deallocate(vm_object_t object)
temp->generation++;
object->backing_object = NULL;
}
vm_object_terminate(object);
/* unlocks and deallocates object */
/*
* Don't double-terminate, we could be in a termination
* recursion due to the terminate having to sync data
* to disk.
*/
if ((object->flags & OBJ_DEAD) == 0)
vm_object_terminate(object);
object = temp;
}
}
@ -627,7 +635,17 @@ vm_object_page_clean(vm_object_t object, vm_pindex_t start, vm_pindex_t end, int
}
if (clearobjflags && (tstart == 0) && (tend == object->size)) {
struct vnode *vp;
vm_object_clear_flag(object, OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
if (object->type == OBJT_VNODE &&
(vp = (struct vnode *)object->handle) != NULL) {
if (vp->v_flag & VOBJDIRTY) {
mtx_lock(&vp->v_interlock);
vp->v_flag &= ~VOBJDIRTY;
mtx_unlock(&vp->v_interlock);
}
}
}
rescan:
@ -1357,6 +1375,8 @@ vm_object_collapse(vm_object_t object)
* and no object references within it, all that is
* necessary is to dispose of it.
*/
KASSERT(backing_object->ref_count == 1, ("backing_object %p was somehow re-referenced during collapse!", backing_object));
KASSERT(TAILQ_FIRST(&backing_object->memq) == NULL, ("backing_object %p somehow has left over pages during collapse!", backing_object));
TAILQ_REMOVE(
&vm_object_list,
@ -1684,6 +1704,23 @@ vm_object_in_map(vm_object_t object)
return 0;
}
void
vm_object_set_writeable_dirty(vm_object_t object)
{
struct vnode *vp;
vm_object_set_flag(object, OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
if (object->type == OBJT_VNODE &&
(vp = (struct vnode *)object->handle) != NULL) {
if ((vp->v_flag & VOBJDIRTY) == 0) {
mtx_lock(&vp->v_interlock);
vp->v_flag |= VOBJDIRTY;
mtx_unlock(&vp->v_interlock);
}
}
}
DB_SHOW_COMMAND(vmochk, vm_object_check)
{
vm_object_t object;

1
sys/vm/vm_object.h
View File

@ -184,6 +184,7 @@ void vm_object_collapse (vm_object_t);
void vm_object_deallocate (vm_object_t);
void vm_object_terminate (vm_object_t);
void vm_object_vndeallocate (vm_object_t);
void vm_object_set_writeable_dirty (vm_object_t);
void vm_object_init (void);
void vm_object_page_clean (vm_object_t, vm_pindex_t, vm_pindex_t, boolean_t);
void vm_object_page_remove (vm_object_t, vm_pindex_t, vm_pindex_t, boolean_t);

2
sys/vm/vm_page.c
View File

@ -609,7 +609,7 @@ vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
* update the object's OBJ_WRITEABLE and OBJ_MIGHTBEDIRTY flags.
*/
if (m->flags & PG_WRITEABLE)
vm_object_set_flag(object, OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
vm_object_set_writeable_dirty(object);
}
/*