FreeBSD/Linux Kernel Cross Reference
sys/vm/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.
     *
     *      from: @(#)vm_page.h     8.2 (Berkeley) 12/13/93
     *
     *
     * 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  Software.Distribution@CS.CMU.EDU
     *  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.
     *
     * $FreeBSD$
     */
    
    #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);
    
    #ifndef VM_BATCHQUEUE_SIZE
    #define VM_BATCHQUEUE_SIZE      7
    #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. */
           u_int vmd_domain;               /* (c) Domain number. */
           u_int vmd_page_count;           /* (c) Total page count. */
           long vmd_segs;                  /* (c) bitmask of the segments */
           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. */
           boolean_t vmd_oom;
           u_int vmd_inactive_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. */
           volatile u_int vmd_addl_shortage;       /* Shortage accumulator. */
           volatile u_int vmd_inactive_freed;      /* Successful inactive frees. */
           volatile u_int vmd_inactive_us;         /* 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_insert(struct vm_batchqueue *bq, vm_page_t m)
   {
   
           if (bq->bq_cnt < nitems(bq->bq_pa)) {
                   bq->bq_pa[bq->bq_cnt++] = m;
                   return (true);
           }
           return (false);
   }
   
   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_ */

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