vm_pagequeue.h

/*-
 * SPDX-License-Identifier: (BSD-3-Clause AND MIT-CMU)
 *
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * The Mach Operating System project at Carnegie-Mellon University.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *
 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
 * All rights reserved.
 *
 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
 *
 * Permission to use, copy, modify and distribute this software and
 * its documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  [email protected]
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie the
 * rights to redistribute these changes.
 */

#ifndef	_VM_PAGEQUEUE_
#define	_VM_PAGEQUEUE_

#ifdef _KERNEL
struct vm_pagequeue {
	struct mtx	pq_mutex;
	struct pglist	pq_pl;
	int		pq_cnt;
	const char	* const pq_name;
	uint64_t	pq_pdpages;
} __aligned(CACHE_LINE_SIZE);

#if __SIZEOF_LONG__ == 8
#define	VM_BATCHQUEUE_SIZE	63
#else
#define	VM_BATCHQUEUE_SIZE	15
#endif

struct vm_batchqueue {
	vm_page_t	bq_pa[VM_BATCHQUEUE_SIZE];
	int		bq_cnt;
} __aligned(CACHE_LINE_SIZE);

#include <vm/uma.h>
#include <sys/_blockcount.h>
#include <sys/pidctrl.h>
struct sysctl_oid;

/*
 * One vm_domain per NUMA domain.  Contains pagequeues, free page structures,
 * and accounting.
 *
 * Lock Key:
 * f	vmd_free_mtx
 * p	vmd_pageout_mtx
 * d	vm_domainset_lock
 * a	atomic
 * c	const after boot
 * q	page queue lock
 *
 * A unique page daemon thread manages each vm_domain structure and is
 * responsible for ensuring that some free memory is available by freeing
 * inactive pages and aging active pages.  To decide how many pages to process,
 * it uses thresholds derived from the number of pages in the domain:
 *
 *  vmd_page_count
 *       ---
 *        |
 *        |-> vmd_inactive_target (~3%)
 *        |   - The active queue scan target is given by
 *        |     (vmd_inactive_target + vmd_free_target - vmd_free_count).
 *        |
 *        |
 *        |-> vmd_free_target (~2%)
 *        |   - Target for page reclamation.
 *        |
 *        |-> vmd_pageout_wakeup_thresh (~1.8%)
 *        |   - Threshold for waking up the page daemon.
 *        |
 *        |
 *        |-> vmd_free_min (~0.5%)
 *        |   - First low memory threshold.
 *        |   - Causes per-CPU caching to be lazily disabled in UMA.
 *        |   - vm_wait() sleeps below this threshold.
 *        |
 *        |-> vmd_free_severe (~0.25%)
 *        |   - Second low memory threshold.
 *        |   - Triggers aggressive UMA reclamation, disables delayed buffer
 *        |     writes.
 *        |
 *        |-> vmd_free_reserved (~0.13%)
 *        |   - Minimum for VM_ALLOC_NORMAL page allocations.
 *        |-> vmd_pageout_free_min (32 + 2 pages)
 *        |   - Minimum for waking a page daemon thread sleeping in vm_wait().
 *        |-> vmd_interrupt_free_min (2 pages)
 *        |   - Minimum for VM_ALLOC_SYSTEM page allocations.
 *       ---
 *
 *--
 * Free page count regulation:
 *
 * The page daemon attempts to ensure that the free page count is above the free
 * target.  It wakes up periodically (every 100ms) to input the current free
 * page shortage (free_target - free_count) to a PID controller, which in
 * response outputs the number of pages to attempt to reclaim.  The shortage's
 * current magnitude, rate of change, and cumulative value are together used to
 * determine the controller's output.  The page daemon target thus adapts
 * dynamically to the system's demand for free pages, resulting in less
 * burstiness than a simple hysteresis loop.
 *
 * When the free page count drops below the wakeup threshold,
 * vm_domain_allocate() proactively wakes up the page daemon.  This helps ensure
 * that the system responds promptly to a large instantaneous free page
 * shortage.
 *
 * The page daemon also attempts to ensure that some fraction of the system's
 * memory is present in the inactive (I) and laundry (L) page queues, so that it
 * can respond promptly to a sudden free page shortage.  In particular, the page
 * daemon thread aggressively scans active pages so long as the following
 * condition holds:
 *
 *         len(I) + len(L) + free_target - free_count < inactive_target
 *
 * Otherwise, when the inactive target is met, the page daemon periodically
 * scans a small portion of the active queue in order to maintain up-to-date
 * per-page access history.  Unreferenced pages in the active queue thus
 * eventually migrate to the inactive queue.
 *
 * The per-domain laundry thread periodically launders dirty pages based on the
 * number of clean pages freed by the page daemon since the last laundering.  If
 * the page daemon fails to meet its scan target (i.e., the PID controller
 * output) because of a shortage of clean inactive pages, the laundry thread
 * attempts to launder enough pages to meet the free page target.
 *
 *--
 * Page allocation priorities:
 *
 * The system defines three page allocation priorities: VM_ALLOC_NORMAL,
 * VM_ALLOC_SYSTEM and VM_ALLOC_INTERRUPT.  An interrupt-priority allocation can
 * claim any free page.  This priority is used in the pmap layer when attempting
 * to allocate a page for the kernel page tables; in such cases an allocation
 * failure will usually result in a kernel panic.  The system priority is used
 * for most other kernel memory allocations, for instance by UMA's slab
 * allocator or the buffer cache.  Such allocations will fail if the free count
 * is below interrupt_free_min.  All other allocations occur at the normal
 * priority, which is typically used for allocation of user pages, for instance
 * in the page fault handler or when allocating page table pages or pv_entry
 * structures for user pmaps.  Such allocations fail if the free count is below
 * the free_reserved threshold.
 *
 *--
 * Free memory shortages:
 *
 * The system uses the free_min and free_severe thresholds to apply
 * back-pressure and give the page daemon a chance to recover.  When a page
 * allocation fails due to a shortage and the allocating thread cannot handle
 * failure, it may call vm_wait() to sleep until free pages are available.
 * vm_domain_freecnt_inc() wakes sleeping threads once the free page count rises
 * above the free_min threshold; the page daemon and laundry threads are given
 * priority and will wake up once free_count reaches the (much smaller)
 * pageout_free_min threshold.
 *
 * On NUMA systems, the domainset iterators always prefer NUMA domains where the
 * free page count is above the free_min threshold.  This means that given the
 * choice between two NUMA domains, one above the free_min threshold and one
 * below, the former will be used to satisfy the allocation request regardless
 * of the domain selection policy.
 *
 * In addition to reclaiming memory from the page queues, the vm_lowmem event
 * fires every ten seconds so long as the system is under memory pressure (i.e.,
 * vmd_free_count < vmd_free_target).  This allows kernel subsystems to register
 * for notifications of free page shortages, upon which they may shrink their
 * caches.  Following a vm_lowmem event, UMA's caches are pruned to ensure that
 * they do not contain an excess of unused memory.  When a domain is below the
 * free_min threshold, UMA limits the population of per-CPU caches.  When a
 * domain falls below the free_severe threshold, UMA's caches are completely
 * drained.
 *
 * If the system encounters a global memory shortage, it may resort to the
 * out-of-memory (OOM) killer, which selects a process and delivers SIGKILL in a
 * last-ditch attempt to free up some pages.  Either of the two following
 * conditions will activate the OOM killer:
 *
 *  1. The page daemons collectively fail to reclaim any pages during their
 *     inactive queue scans.  After vm_pageout_oom_seq consecutive scans fail,
 *     the page daemon thread votes for an OOM kill, and an OOM kill is
 *     triggered when all page daemons have voted.  This heuristic is strict and
 *     may fail to trigger even when the system is effectively deadlocked.
 *
 *  2. Threads in the user fault handler are repeatedly unable to make progress
 *     while allocating a page to satisfy the fault.  After
 *     vm_pfault_oom_attempts page allocation failures with intervening
 *     vm_wait() calls, the faulting thread will trigger an OOM kill.
 */
struct vm_domain {
	struct vm_pagequeue vmd_pagequeues[PQ_COUNT];
	struct mtx_padalign vmd_free_mtx;
	struct mtx_padalign vmd_pageout_mtx;
	struct vm_pgcache {
		int domain;
		int pool;
		uma_zone_t zone;
	} vmd_pgcache[VM_NFREEPOOL];
	struct vmem *vmd_kernel_arena;	/* (c) per-domain kva R/W arena. */
	struct vmem *vmd_kernel_rwx_arena; /* (c) per-domain kva R/W/X arena. */
	struct vmem *vmd_kernel_nofree_arena; /* (c) per-domain kva NOFREE arena. */
	u_int vmd_domain;		/* (c) Domain number. */
	u_int vmd_page_count;		/* (c) Total page count. */
	long vmd_segs;			/* (c) bitmask of the segments */
	struct pglist vmd_nofreeq;	/* (f) NOFREE page bump allocator. */
	u_int __aligned(CACHE_LINE_SIZE) vmd_free_count; /* (a,f) free page count */
	u_int vmd_pageout_deficit;	/* (a) Estimated number of pages deficit */
	uint8_t vmd_pad[CACHE_LINE_SIZE - (sizeof(u_int) * 2)];

	/* Paging control variables, used within single threaded page daemon. */
	struct pidctrl vmd_pid;		/* Pageout controller. */
	bool vmd_oom;			/* An OOM kill was requested. */
	bool vmd_helper_threads_enabled;/* Use multiple threads to scan. */
	u_int vmd_inactive_threads;	/* Number of extra helper threads. */
	u_int vmd_inactive_shortage;		/* Per-thread shortage. */
	blockcount_t vmd_inactive_running;	/* Number of inactive threads. */
	blockcount_t vmd_inactive_starting;	/* Number of threads started. */
	u_int vmd_addl_shortage;	/* (a) Shortage accumulator. */
	u_int vmd_inactive_freed;	/* (a) Successful inactive frees. */
	u_int vmd_inactive_us;		/* (a) Microseconds for above. */
	u_int vmd_inactive_pps;		/* Exponential decay frees/second. */
	int vmd_oom_seq;
	int vmd_last_active_scan;
	struct vm_page vmd_markers[PQ_COUNT]; /* (q) markers for queue scans */
	struct vm_page vmd_inacthead; /* marker for LRU-defeating insertions */
	struct vm_page vmd_clock[2]; /* markers for active queue scan */

	int vmd_pageout_wanted;		/* (a, p) pageout daemon wait channel */
	int vmd_pageout_pages_needed;	/* (d) page daemon waiting for pages? */
	bool vmd_minset;		/* (d) Are we in vm_min_domains? */
	bool vmd_severeset;		/* (d) Are we in vm_severe_domains? */
	enum {
		VM_LAUNDRY_IDLE = 0,
		VM_LAUNDRY_BACKGROUND,
		VM_LAUNDRY_SHORTFALL
	} vmd_laundry_request;

	/* Paging thresholds and targets. */
	u_int vmd_clean_pages_freed;	/* (q) accumulator for laundry thread */
	u_int vmd_background_launder_target; /* (c) */
	u_int vmd_free_reserved;	/* (c) pages reserved for deadlock */
	u_int vmd_free_target;		/* (c) pages desired free */
	u_int vmd_free_min;		/* (c) pages desired free */
	u_int vmd_inactive_target;	/* (c) pages desired inactive */
	u_int vmd_pageout_free_min;	/* (c) min pages reserved for kernel */
	u_int vmd_pageout_wakeup_thresh;/* (c) min pages to wake pagedaemon */
	u_int vmd_interrupt_free_min;	/* (c) reserved pages for int code */
	u_int vmd_free_severe;		/* (c) severe page depletion point */

	/* Name for sysctl etc. */
	struct sysctl_oid *vmd_oid;
	char vmd_name[sizeof(__XSTRING(MAXMEMDOM))];
} __aligned(CACHE_LINE_SIZE);

extern struct vm_domain vm_dom[MAXMEMDOM];

#define	VM_DOMAIN(n)		(&vm_dom[(n)])
#define	VM_DOMAIN_EMPTY(n)	(vm_dom[(n)].vmd_page_count == 0)

#define	vm_pagequeue_assert_locked(pq)	mtx_assert(&(pq)->pq_mutex, MA_OWNED)
#define	vm_pagequeue_lock(pq)		mtx_lock(&(pq)->pq_mutex)
#define	vm_pagequeue_lockptr(pq)	(&(pq)->pq_mutex)
#define	vm_pagequeue_trylock(pq)	mtx_trylock(&(pq)->pq_mutex)
#define	vm_pagequeue_unlock(pq)		mtx_unlock(&(pq)->pq_mutex)

#define	vm_domain_free_assert_locked(n)					\
	    mtx_assert(vm_domain_free_lockptr((n)), MA_OWNED)
#define	vm_domain_free_assert_unlocked(n)				\
	    mtx_assert(vm_domain_free_lockptr((n)), MA_NOTOWNED)
#define	vm_domain_free_lock(d)						\
	    mtx_lock(vm_domain_free_lockptr((d)))
#define	vm_domain_free_lockptr(d)					\
	    (&(d)->vmd_free_mtx)
#define	vm_domain_free_trylock(d)					\
	    mtx_trylock(vm_domain_free_lockptr((d)))
#define	vm_domain_free_unlock(d)					\
	    mtx_unlock(vm_domain_free_lockptr((d)))

#define	vm_domain_pageout_lockptr(d)					\
	    (&(d)->vmd_pageout_mtx)
#define	vm_domain_pageout_assert_locked(n)				\
	    mtx_assert(vm_domain_pageout_lockptr((n)), MA_OWNED)
#define	vm_domain_pageout_assert_unlocked(n)				\
	    mtx_assert(vm_domain_pageout_lockptr((n)), MA_NOTOWNED)
#define	vm_domain_pageout_lock(d)					\
	    mtx_lock(vm_domain_pageout_lockptr((d)))
#define	vm_domain_pageout_unlock(d)					\
	    mtx_unlock(vm_domain_pageout_lockptr((d)))

static __inline void
vm_pagequeue_cnt_add(struct vm_pagequeue *pq, int addend)
{

	vm_pagequeue_assert_locked(pq);
	pq->pq_cnt += addend;
}
#define	vm_pagequeue_cnt_inc(pq)	vm_pagequeue_cnt_add((pq), 1)
#define	vm_pagequeue_cnt_dec(pq)	vm_pagequeue_cnt_add((pq), -1)

static inline void
vm_pagequeue_remove(struct vm_pagequeue *pq, vm_page_t m)
{

	TAILQ_REMOVE(&pq->pq_pl, m, plinks.q);
	vm_pagequeue_cnt_dec(pq);
}

static inline void
vm_batchqueue_init(struct vm_batchqueue *bq)
{

	bq->bq_cnt = 0;
}

static inline bool
vm_batchqueue_empty(const struct vm_batchqueue *bq)
{
	return (bq->bq_cnt == 0);
}

static inline int
vm_batchqueue_insert(struct vm_batchqueue *bq, vm_page_t m)
{
	int slots_free;

	slots_free = nitems(bq->bq_pa) - bq->bq_cnt;
	if (slots_free > 0) {
		bq->bq_pa[bq->bq_cnt++] = m;
		return (slots_free);
	}
	return (slots_free);
}

static inline vm_page_t
vm_batchqueue_pop(struct vm_batchqueue *bq)
{

	if (bq->bq_cnt == 0)
		return (NULL);
	return (bq->bq_pa[--bq->bq_cnt]);
}

void vm_domain_set(struct vm_domain *vmd);
void vm_domain_clear(struct vm_domain *vmd);
int vm_domain_allocate(struct vm_domain *vmd, int req, int npages);

/*
 *      vm_pagequeue_domain:
 *
 *      Return the memory domain the page belongs to.
 */
static inline struct vm_domain *
vm_pagequeue_domain(vm_page_t m)
{

	return (VM_DOMAIN(vm_page_domain(m)));
}

/*
 * Return the number of pages we need to free-up or cache
 * A positive number indicates that we do not have enough free pages.
 */
static inline int
vm_paging_target(struct vm_domain *vmd)
{

	return (vmd->vmd_free_target - vmd->vmd_free_count);
}

/*
 * Returns TRUE if the pagedaemon needs to be woken up.
 */
static inline int
vm_paging_needed(struct vm_domain *vmd, u_int free_count)
{

	return (free_count < vmd->vmd_pageout_wakeup_thresh);
}

/*
 * Returns TRUE if the domain is below the min paging target.
 */
static inline int
vm_paging_min(struct vm_domain *vmd)
{

        return (vmd->vmd_free_min > vmd->vmd_free_count);
}

/*
 * Returns TRUE if the domain is below the severe paging target.
 */
static inline int
vm_paging_severe(struct vm_domain *vmd)
{

        return (vmd->vmd_free_severe > vmd->vmd_free_count);
}

/*
 * Return the number of pages we need to launder.
 * A positive number indicates that we have a shortfall of clean pages.
 */
static inline int
vm_laundry_target(struct vm_domain *vmd)
{

	return (vm_paging_target(vmd));
}

void pagedaemon_wakeup(int domain);

static inline void
vm_domain_freecnt_inc(struct vm_domain *vmd, int adj)
{
	u_int old, new;

	old = atomic_fetchadd_int(&vmd->vmd_free_count, adj);
	new = old + adj;
	/*
	 * Only update bitsets on transitions.  Notice we short-circuit the
	 * rest of the checks if we're above min already.
	 */
	if (old < vmd->vmd_free_min && (new >= vmd->vmd_free_min ||
	    (old < vmd->vmd_free_severe && new >= vmd->vmd_free_severe) ||
	    (old < vmd->vmd_pageout_free_min &&
	    new >= vmd->vmd_pageout_free_min)))
		vm_domain_clear(vmd);
}

#endif	/* _KERNEL */
#endif				/* !_VM_PAGEQUEUE_ */