> From: David Gwynne <[email protected]>
> Date: Mon, 8 Aug 2016 23:14:13 +1000
>
> > On 8 Aug 2016, at 10:46 PM, Mark Kettenis <[email protected]> wrote:
> >
> >> Date: Mon, 8 Aug 2016 21:56:23 +1000
> >> From: David Gwynne <[email protected]>
> >>
> >> the current tracking of free static map entries is done as hand
> >> rolled list manipulations using pointers in an rb_entry. it's really
> >> confusing to read.
> >>
> >> since its simple list manipulations, this replaces the hand rolled
> >> code with an SLIST.
> >>
> >> ok?
> >
> > I like this. How does this change the way entries are recycled? The
> > new code will use the last entry that was freed. Was this the case
> > with the old code as well?
>
> the RB version put free items on the head (uvm.kentry_free) and removed them
> from there too. the SLIST ops are the same in that respect.
>
> i think the order that new entries from a fresh page are added in
> uvm_mapent_alloc is different, but that is not the hot path by any
> means.
I don't really worry about tat path anyway.
Thanks for the explanation; ok kettenis@
> >> Index: uvm.h
> >> ===================================================================
> >> RCS file: /cvs/src/sys/uvm/uvm.h,v
> >> retrieving revision 1.60
> >> diff -u -p -r1.60 uvm.h
> >> --- uvm.h 8 Oct 2015 15:58:38 -0000 1.60
> >> +++ uvm.h 8 Aug 2016 11:53:57 -0000
> >> @@ -69,7 +69,7 @@ struct uvm {
> >> struct mutex aiodoned_lock;
> >>
> >> /* static kernel map entry pool */
> >> - vm_map_entry_t kentry_free; /* free page pool */
> >> + SLIST_HEAD(, vm_map_entry) kentry_free; /* free page pool */
> >>
> >> /* aio_done is locked by uvm.aiodoned_lock. */
> >> TAILQ_HEAD(, buf) aio_done; /* done async i/o reqs */
> >> Index: uvm_map.c
> >> ===================================================================
> >> RCS file: /cvs/src/sys/uvm/uvm_map.c,v
> >> retrieving revision 1.219
> >> diff -u -p -r1.219 uvm_map.c
> >> --- uvm_map.c 30 Jul 2016 16:43:44 -0000 1.219
> >> +++ uvm_map.c 8 Aug 2016 11:53:57 -0000
> >> @@ -1669,25 +1669,23 @@ uvm_mapent_alloc(struct vm_map *map, int
> >>
> >> if (map->flags & VM_MAP_INTRSAFE || cold) {
> >> mtx_enter(&uvm_kmapent_mtx);
> >> - me = uvm.kentry_free;
> >> - if (me == NULL) {
> >> + if (SLIST_EMPTY(&uvm.kentry_free)) {
> >> ne = km_alloc(PAGE_SIZE, &kv_page, &kp_dirty,
> >> &kd_nowait);
> >> if (ne == NULL)
> >> panic("uvm_mapent_alloc: cannot allocate map "
> >> "entry");
> >> - for (i = 0;
> >> - i < PAGE_SIZE / sizeof(struct vm_map_entry) - 1;
> >> - i++)
> >> - RB_LEFT(&ne[i], daddrs.addr_entry) = &ne[i + 1];
> >> - RB_LEFT(&ne[i], daddrs.addr_entry) = NULL;
> >> - me = ne;
> >> + for (i = 0; i < PAGE_SIZE / sizeof(*ne); i++) {
> >> + SLIST_INSERT_HEAD(&uvm.kentry_free,
> >> + &ne[i], daddrs.addr_kentry);
> >> + }
> >> if (ratecheck(&uvm_kmapent_last_warn_time,
> >> &uvm_kmapent_warn_rate))
> >> printf("uvm_mapent_alloc: out of static "
> >> "map entries\n");
> >> }
> >> - uvm.kentry_free = RB_LEFT(me, daddrs.addr_entry);
> >> + me = SLIST_FIRST(&uvm.kentry_free);
> >> + SLIST_REMOVE_HEAD(&uvm.kentry_free, daddrs.addr_kentry);
> >> uvmexp.kmapent++;
> >> mtx_leave(&uvm_kmapent_mtx);
> >> me->flags = UVM_MAP_STATIC;
> >> @@ -1725,8 +1723,7 @@ uvm_mapent_free(struct vm_map_entry *me)
> >> {
> >> if (me->flags & UVM_MAP_STATIC) {
> >> mtx_enter(&uvm_kmapent_mtx);
> >> - RB_LEFT(me, daddrs.addr_entry) = uvm.kentry_free;
> >> - uvm.kentry_free = me;
> >> + SLIST_INSERT_HEAD(&uvm.kentry_free, me, daddrs.addr_kentry);
> >> uvmexp.kmapent--;
> >> mtx_leave(&uvm_kmapent_mtx);
> >> } else if (me->flags & UVM_MAP_KMEM) {
> >> @@ -2795,11 +2792,10 @@ uvm_map_init(void)
> >>
> >> /* now set up static pool of kernel map entries ... */
> >> mtx_init(&uvm_kmapent_mtx, IPL_VM);
> >> - uvm.kentry_free = NULL;
> >> + SLIST_INIT(&uvm.kentry_free);
> >> for (lcv = 0 ; lcv < MAX_KMAPENT ; lcv++) {
> >> - RB_LEFT(&kernel_map_entry[lcv], daddrs.addr_entry) =
> >> - uvm.kentry_free;
> >> - uvm.kentry_free = &kernel_map_entry[lcv];
> >> + SLIST_INSERT_HEAD(&uvm.kentry_free,
> >> + &kernel_map_entry[lcv], daddrs.addr_kentry);
> >> }
> >>
> >> /* initialize the map-related pools. */
> >> Index: uvm_map.h
> >> ===================================================================
> >> RCS file: /cvs/src/sys/uvm/uvm_map.h,v
> >> retrieving revision 1.55
> >> diff -u -p -r1.55 uvm_map.h
> >> --- uvm_map.h 9 Sep 2015 23:33:37 -0000 1.55
> >> +++ uvm_map.h 8 Aug 2016 11:53:57 -0000
> >> @@ -161,6 +161,7 @@ union vm_map_object {
> >> struct vm_map_entry {
> >> union {
> >> RB_ENTRY(vm_map_entry) addr_entry; /* address tree */
> >> + SLIST_ENTRY(vm_map_entry) addr_kentry;
> >> } daddrs;
> >>
> >> union {
> >>
> >>
>
>
>
