> Date: Sun, 15 Jan 2017 15:06:50 +0100
> From: Stefan Kempf <sisnk...@gmail.com>
>
> When uvm pivots are enabled, allocations
> with an address hint provided by the user program are
> handled by the uaddr_hint selector.
>
> I'd like to remove the uaddr_hint selector. The uaddr_rnd selector
> already deals with hinted allocations correctly, so why not use
> it for hinted allocations in the pivot selector?
>
> This diff is a part of making pivots work.
> Getting rid of the hint selectors makes the code simpler.
> I'd to commit this part first, to make the actual pivot
> diffs smaller.
>
> ok?
No objection from me.
> Some more details:
>
> If you have multiple selectors per address space that manage
> overlapping address ranges, some selectors have priority
> over others. E.g. only the brk selector is allowed to make
> allocations within the brk area. The rnd selector
> gets all these checks right, but the hint selector does
> not, which causes panics when you use pivots and try to
> do a hinted allocation within the brk area.
>
> So better use the code which is known to work for hinted
> allocations. Once pivots are enabled, maybe the parts of the
> rnd allocator that deal with hinted allocations can be factored
> out into a common function.
>
> Index: uvm/uvm_addr.c
> ===================================================================
> RCS file: /cvs/src/sys/uvm/uvm_addr.c,v
> retrieving revision 1.22
> diff -u -p -r1.22 uvm_addr.c
> --- uvm/uvm_addr.c 16 Sep 2016 02:50:54 -0000 1.22
> +++ uvm/uvm_addr.c 14 Jan 2017 05:53:17 -0000
> @@ -46,17 +46,10 @@
>
> /* Pool with uvm_addr_state structures. */
> struct pool uaddr_pool;
> -struct pool uaddr_hint_pool;
> struct pool uaddr_bestfit_pool;
> struct pool uaddr_pivot_pool;
> struct pool uaddr_rnd_pool;
>
> -/* uvm_addr state for hint based selector. */
> -struct uaddr_hint_state {
> - struct uvm_addr_state uaddr;
> - vsize_t max_dist;
> -};
> -
> /* uvm_addr state for bestfit selector. */
> struct uaddr_bestfit_state {
> struct uvm_addr_state ubf_uaddr;
> @@ -118,7 +111,6 @@ void uaddr_kremove(struct vm_map *,
> void uaddr_kbootstrapdestroy(struct uvm_addr_state *);
>
> void uaddr_destroy(struct uvm_addr_state *);
> -void uaddr_hint_destroy(struct uvm_addr_state *);
> void uaddr_kbootstrap_destroy(struct uvm_addr_state *);
> void uaddr_rnd_destroy(struct uvm_addr_state *);
> void uaddr_bestfit_destroy(struct uvm_addr_state *);
> @@ -138,10 +130,6 @@ int uaddr_rnd_select(struct vm_map
> *,
> struct uvm_addr_state *, struct vm_map_entry **,
> vaddr_t *, vsize_t, vaddr_t, vaddr_t, vm_prot_t,
> vaddr_t);
> -int uaddr_hint_select(struct vm_map *,
> - struct uvm_addr_state*, struct vm_map_entry **,
> - vaddr_t *, vsize_t, vaddr_t, vaddr_t, vm_prot_t,
> - vaddr_t);
> int uaddr_bestfit_select(struct vm_map *,
> struct uvm_addr_state*, struct vm_map_entry **,
> vaddr_t *, vsize_t, vaddr_t, vaddr_t, vm_prot_t,
> @@ -290,8 +278,6 @@ uvm_addr_init(void)
> {
> pool_init(&uaddr_pool, sizeof(struct uvm_addr_state), 0,
> IPL_VM, PR_WAITOK, "uaddr", NULL);
> - pool_init(&uaddr_hint_pool, sizeof(struct uaddr_hint_state), 0,
> - IPL_VM, PR_WAITOK, "uaddrhint", NULL);
> pool_init(&uaddr_bestfit_pool, sizeof(struct uaddr_bestfit_state), 0,
> IPL_VM, PR_WAITOK, "uaddrbest", NULL);
> pool_init(&uaddr_pivot_pool, sizeof(struct uaddr_pivot_state), 0,
> @@ -740,116 +726,6 @@ uaddr_rnd_print(struct uvm_addr_state *u
> #endif
>
> /*
> - * An allocator that selects an address within distance of the hint.
> - *
> - * If no hint is given, the allocator refuses to allocate.
> - */
> -const struct uvm_addr_functions uaddr_hint_functions = {
> - .uaddr_select = &uaddr_hint_select,
> - .uaddr_destroy = &uaddr_hint_destroy,
> - .uaddr_name = "uaddr_hint"
> -};
> -
> -/*
> - * Create uaddr_hint state.
> - */
> -struct uvm_addr_state *
> -uaddr_hint_create(vaddr_t minaddr, vaddr_t maxaddr, vsize_t max_dist)
> -{
> - struct uaddr_hint_state *ua_hint;
> -
> - KASSERT(uaddr_hint_pool.pr_size == sizeof(*ua_hint));
> -
> - ua_hint = pool_get(&uaddr_hint_pool, PR_WAITOK);
> - ua_hint->uaddr.uaddr_minaddr = minaddr;
> - ua_hint->uaddr.uaddr_maxaddr = maxaddr;
> - ua_hint->uaddr.uaddr_functions = &uaddr_hint_functions;
> - ua_hint->max_dist = max_dist;
> - return &ua_hint->uaddr;
> -}
> -
> -/*
> - * Destroy uaddr_hint state.
> - */
> -void
> -uaddr_hint_destroy(struct uvm_addr_state *uaddr)
> -{
> - pool_put(&uaddr_hint_pool, uaddr);
> -}
> -
> -/*
> - * Hint selector.
> - *
> - * Attempts to find an address that is within max_dist of the hint.
> - */
> -int
> -uaddr_hint_select(struct vm_map *map, struct uvm_addr_state *uaddr_param,
> - struct vm_map_entry **entry_out, vaddr_t *addr_out,
> - vsize_t sz, vaddr_t align, vaddr_t offset,
> - vm_prot_t prot, vaddr_t hint)
> -{
> - struct uaddr_hint_state *uaddr =
> - (struct uaddr_hint_state *)uaddr_param;
> - vsize_t before_gap, after_gap;
> - vaddr_t low, high;
> - int dir;
> -
> - if (hint == 0)
> - return ENOMEM;
> -
> - /* Calculate upper and lower bound for selected address. */
> - high = hint + uaddr->max_dist;
> - if (high < hint) /* overflow */
> - high = map->max_offset;
> - high = MIN(high, uaddr->uaddr.uaddr_maxaddr);
> - if (high < sz)
> - return ENOMEM; /* Protect against underflow. */
> - high -= sz;
> -
> - /* Calculate lower bound for selected address. */
> - low = hint - uaddr->max_dist;
> - if (low > hint) /* underflow */
> - low = map->min_offset;
> - low = MAX(low, uaddr->uaddr.uaddr_minaddr);
> -
> - /* Search strategy setup. */
> - before_gap = PAGE_SIZE +
> - (arc4random_uniform(UADDR_HINT_MAXGAP) & ~(vaddr_t)PAGE_MASK);
> - after_gap = PAGE_SIZE +
> - (arc4random_uniform(UADDR_HINT_MAXGAP) & ~(vaddr_t)PAGE_MASK);
> - dir = (arc4random() & 0x01) ? 1 : -1;
> -
> - /*
> - * Try to search:
> - * - forward, with gap
> - * - backward, with gap
> - * - forward, without gap
> - * - backward, without gap
> - * (Where forward is in the direction specified by dir and
> - * backward is in the direction specified by -dir).
> - */
> - if (uvm_addr_linsearch(map, uaddr_param,
> - entry_out, addr_out, hint, sz, align, offset,
> - dir, low, high, before_gap, after_gap) == 0)
> - return 0;
> - if (uvm_addr_linsearch(map, uaddr_param,
> - entry_out, addr_out, hint, sz, align, offset,
> - -dir, low, high, before_gap, after_gap) == 0)
> - return 0;
> -
> - if (uvm_addr_linsearch(map, uaddr_param,
> - entry_out, addr_out, hint, sz, align, offset,
> - dir, low, high, 0, 0) == 0)
> - return 0;
> - if (uvm_addr_linsearch(map, uaddr_param,
> - entry_out, addr_out, hint, sz, align, offset,
> - -dir, low, high, 0, 0) == 0)
> - return 0;
> -
> - return ENOMEM;
> -}
> -
> -/*
> * Kernel allocation bootstrap logic.
> */
> const struct uvm_addr_functions uaddr_kernel_functions = {
> @@ -1242,9 +1118,16 @@ uaddr_pivot_select(struct vm_map *map, s
> vsize_t before_gap, after_gap;
> int err;
>
> - /* Hint must be handled by dedicated hint allocator. */
> - if (hint != 0)
> - return EINVAL;
> + /*
> + * When we have a hint, use the rnd allocator that finds the
> + * area that is closest to the hint, if there is such an area.
> + */
> + if (hint != 0) {
> + if (uaddr_rnd_select(map, uaddr_p, entry_out, addr_out,
> + sz, align, offset, prot, hint) == 0)
> + return 0;
> + return ENOMEM;
> + }
>
> /*
> * Select a random pivot and a random gap sizes around the allocation.
> Index: uvm/uvm_addr.h
> ===================================================================
> RCS file: /cvs/src/sys/uvm/uvm_addr.h,v
> retrieving revision 1.6
> diff -u -p -r1.6 uvm_addr.h
> --- uvm/uvm_addr.h 16 Sep 2016 01:51:40 -0000 1.6
> +++ uvm/uvm_addr.h 14 Jan 2017 05:53:17 -0000
> @@ -90,7 +90,6 @@ int uvm_addr_invoke(struct vm_map *,
> struct uvm_addr_state *uaddr_lin_create(vaddr_t, vaddr_t);
> #endif
> struct uvm_addr_state *uaddr_rnd_create(vaddr_t, vaddr_t);
> -struct uvm_addr_state *uaddr_hint_create(vaddr_t, vaddr_t, vsize_t);
> #ifndef SMALL_KERNEL
> struct uvm_addr_state *uaddr_bestfit_create(vaddr_t, vaddr_t);
> struct uvm_addr_state *uaddr_pivot_create(vaddr_t, vaddr_t);
> Index: uvm/uvm_map.c
> ===================================================================
> RCS file: /cvs/src/sys/uvm/uvm_map.c,v
> retrieving revision 1.226
> diff -u -p -r1.226 uvm_map.c
> --- uvm/uvm_map.c 7 Nov 2016 00:26:33 -0000 1.226
> +++ uvm/uvm_map.c 14 Jan 2017 05:53:18 -0000
> @@ -5291,9 +5291,6 @@ uvm_map_setup_md(struct vm_map *map)
> min = VMMAP_MIN_ADDR;
>
> #if 0 /* Cool stuff, not yet */
> - /* Hinted allocations. */
> - map->uaddr_any[1] = uaddr_hint_create(min, max, 1024 * 1024 * 1024);
> -
> /* Executable code is special. */
> map->uaddr_exe = uaddr_rnd_create(min, I386_MAX_EXE_ADDR);
> /* Place normal allocations beyond executable mappings. */
> @@ -5323,13 +5320,6 @@ uvm_map_setup_md(struct vm_map *map)
> min = VMMAP_MIN_ADDR;
>
> #if 0 /* Cool stuff, not yet */
> - /* Hinted allocations above 4GB */
> - map->uaddr_any[0] =
> - uaddr_hint_create(0x100000000ULL, max, 1024 * 1024 * 1024);
> - /* Hinted allocations below 4GB */
> - map->uaddr_any[1] = uaddr_hint_create(min, 0x100000000ULL,
> - 1024 * 1024 * 1024);
> - /* Normal allocations, always above 4GB */
> map->uaddr_any[3] = uaddr_pivot_create(MAX(min, 0x100000000ULL), max);
> #else /* Crappy stuff, for now */
> map->uaddr_any[0] = uaddr_rnd_create(min, max);
> @@ -5356,9 +5346,6 @@ uvm_map_setup_md(struct vm_map *map)
> min = VMMAP_MIN_ADDR;
>
> #if 0 /* Cool stuff, not yet */
> - /* Hinted allocations. */
> - map->uaddr_any[1] = uaddr_hint_create(min, max, 1024 * 1024 * 1024);
> - /* Normal allocations. */
> map->uaddr_any[3] = uaddr_pivot_create(min, max);
> #else /* Crappy stuff, for now */
> map->uaddr_any[0] = uaddr_rnd_create(min, max);
>
>
