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Final commit to remove vnode->v_lastr. vm_fault now handles read

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clustering issues (replacing code that used to be in
    ufs/ufs/ufs_readwrite.c).  vm_fault also now uses the new VM page counter
    inlines.

    This completes the changeover from vnode->v_lastr to vm_entry_t->v_lastr
    for VM, and fp->f_nextread and fp->f_seqcount (which have been in the
    tree for a while).  Determination of the I/O strategy (sequential, random,
    and so forth) is now handled on a descriptor-by-descriptor basis for
    base I/O calls, and on a memory-region-by-memory-region and
    process-by-process basis for VM faults.

Reviewed by:	David Greenman <dg@root.com>, Alan Cox <alc@cs.rice.edu>
This commit is contained in:
Matthew Dillon 1999-09-21 00:36:16 +00:00
parent 67ddfcaf69
commit 40360b1bbb
4 changed files with 43 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
sys/kern/vfs_export.c
View File

@ -566,7 +566,6 @@ getnewvnode(tag, mp, vops, vpp)
}
#endif
vp->v_flag = 0;
vp->v_lastr = 0;
vp->v_lastw = 0;
vp->v_lasta = 0;
vp->v_cstart = 0;

1
sys/kern/vfs_subr.c
View File

@ -566,7 +566,6 @@ getnewvnode(tag, mp, vops, vpp)
}
#endif
vp->v_flag = 0;
vp->v_lastr = 0;
vp->v_lastw = 0;
vp->v_lasta = 0;
vp->v_cstart = 0;

1
sys/sys/vnode.h
View File

@ -87,7 +87,6 @@ struct vnode {
int v_usecount; /* reference count of users */
int v_writecount; /* reference count of writers */
int v_holdcnt; /* page & buffer references */
daddr_t v_lastr; /* last read (read-ahead) */
u_long v_id; /* capability identifier */
struct mount *v_mount; /* ptr to vfs we are in */
vop_t **v_op; /* vnode operations vector */

79
sys/vm/vm_fault.c
View File

@ -153,6 +153,16 @@ _unlock_things(struct faultstate *fs, int dealloc)
#define unlock_things(fs) _unlock_things(fs, 0)
#define unlock_and_deallocate(fs) _unlock_things(fs, 1)
/*
* TRYPAGER - used by vm_fault to calculate whether the pager for the
* current object *might* contain the page.
*
* default objects are zero-fill, there is no real pager.
*/
#define TRYPAGER (fs.object->type != OBJT_DEFAULT && \
(((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired))
/*
* vm_fault:
*
@ -188,12 +198,12 @@ vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags)
hardfault = 0;
RetryFault:;
fs.map = map;
/*
* Find the backing store object and offset into it to begin the
* search.
*/
fs.map = map;
if ((result = vm_map_lookup(&fs.map, vaddr,
fault_type, &fs.entry, &fs.first_object,
&fs.first_pindex, &prot, &wired)) != KERN_SUCCESS) {
@ -308,21 +318,7 @@ RetryFault:;
vm_page_unqueue_nowakeup(fs.m);
splx(s);
/*
* This code is designed to prevent thrashing in a
* low-memory situation by assuming that pages placed
* in the cache are generally inactive, so if a cached
* page is requested and we are low on memory, we try
* to wait for the low-memory condition to be resolved.
*
* This code cannot handle a major memory starvation
* situation where pages are forced into the cache and
* may cause 'good' programs to stall. As of 22Jan99
* the problem is still under discussion and not
* resolved.
*/
if (((queue - fs.m->pc) == PQ_CACHE) &&
(cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_min) {
if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) {
vm_page_activate(fs.m);
unlock_and_deallocate(&fs);
VM_WAIT;
@ -346,14 +342,11 @@ RetryFault:;
}
/*
* Page is not resident, If this is the search termination,
* allocate a new page.
* Page is not resident, If this is the search termination
* or the pager might contain the page, allocate a new page.
*/
if (((fs.object->type != OBJT_DEFAULT) &&
(((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired))
|| (fs.object == fs.first_object)) {
if (TRYPAGER || fs.object == fs.first_object) {
if (fs.pindex >= fs.object->size) {
unlock_and_deallocate(&fs);
return (KERN_PROTECTION_FAILURE);
@ -362,9 +355,11 @@ RetryFault:;
/*
* Allocate a new page for this object/offset pair.
*/
fs.m = vm_page_alloc(fs.object, fs.pindex,
(fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO);
fs.m = NULL;
if (!vm_page_count_severe()) {
fs.m = vm_page_alloc(fs.object, fs.pindex,
(fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO);
}
if (fs.m == NULL) {
unlock_and_deallocate(&fs);
VM_WAIT;
@ -374,14 +369,16 @@ RetryFault:;
readrest:
/*
* Have page, but it may not be entirely valid ( or valid at
* all ). If this object is not the default, try to fault-in
* the page as well as activate additional pages when
* appropriate, and page-in additional pages when appropriate.
* We have found a valid page or we have allocated a new page.
* The page thus may not be valid or may not be entirely
* valid.
*
* Attempt to fault-in the page if there is a chance that the
* pager has it, and potentially fault in additional pages
* at the same time.
*/
if (fs.object->type != OBJT_DEFAULT &&
(((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) {
if (TRYPAGER) {
int rv;
int reqpage;
int ahead, behind;
@ -401,14 +398,17 @@ RetryFault:;
}
if ((fs.first_object->type != OBJT_DEVICE) &&
(behavior == MAP_ENTRY_BEHAV_SEQUENTIAL)) {
(behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
(behavior != MAP_ENTRY_BEHAV_RANDOM &&
fs.pindex >= fs.entry->lastr &&
fs.pindex < fs.entry->lastr + VM_FAULT_READ))
) {
vm_pindex_t firstpindex, tmppindex;
if (fs.first_pindex <
2*(VM_FAULT_READ_BEHIND + VM_FAULT_READ_AHEAD + 1))
if (fs.first_pindex < 2 * VM_FAULT_READ)
firstpindex = 0;
else
firstpindex = fs.first_pindex -
2*(VM_FAULT_READ_BEHIND + VM_FAULT_READ_AHEAD + 1);
firstpindex = fs.first_pindex - 2 * VM_FAULT_READ;
/*
* note: partially valid pages cannot be
@ -459,6 +459,12 @@ RetryFault:;
faultcount = vm_fault_additional_pages(
fs.m, behind, ahead, marray, &reqpage);
/*
* update lastr imperfectly (we do not know how much
* getpages will actually read), but good enough.
*/
fs.entry->lastr = fs.pindex + faultcount - behind;
/*
* Call the pager to retrieve the data, if any, after
* releasing the lock on the map. We hold a ref on
@ -531,6 +537,7 @@ RetryFault:;
*/
}
}
/*
* We get here if the object has default pager (or unwiring)
* or the pager doesn't have the page.