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[/] [or1k/] [trunk/] [rc203soc/] [sw/] [uClinux/] [mm/] [vmscan.c] - Rev 1634
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/* * linux/mm/vmscan.c * * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds * * Swap reorganised 29.12.95, Stephen Tweedie. * kswapd added: 7.1.96 sct * Version: $Id: vmscan.c,v 1.1 2005-12-20 11:47:02 jcastillo Exp $ */ #include <linux/mm.h> #include <linux/sched.h> #include <linux/head.h> #include <linux/kernel.h> #include <linux/kernel_stat.h> #include <linux/errno.h> #include <linux/string.h> #include <linux/stat.h> #include <linux/swap.h> #include <linux/fs.h> #include <linux/swapctl.h> #include <linux/pagemap.h> #include <linux/smp_lock.h> #include <asm/dma.h> #include <asm/system.h> /* for cli()/sti() */ #include <asm/segment.h> /* for memcpy_to/fromfs */ #include <asm/bitops.h> #include <asm/pgtable.h> /* * To check memory consuming code elsewhere set this to 1 */ /* #define MM_DEBUG */ /* * When are we next due for a page scan? */ static int next_swap_jiffies = 0; /* * Was the last kswapd wakeup caused by * nr_free_pages < free_pages_low */ static int last_wakeup_low = 0; /* * How often do we do a pageout scan during normal conditions? * Default is four times a second. */ int swapout_interval = HZ / 4; /* * The wait queue for waking up the pageout daemon: */ static struct wait_queue * kswapd_wait = NULL; /* * We avoid doing a reschedule if the pageout daemon is already awake; */ static int kswapd_awake = 0; /* * sysctl-modifiable parameters to control the aggressiveness of the * page-searching within the kswapd page recovery daemon. */ kswapd_control_t kswapd_ctl = {4, -1, -1, -1, -1}; static void init_swap_timer(void); /* * The swap-out functions return 1 if they successfully * threw something out, and we got a free page. It returns * zero if it couldn't do anything, and any other value * indicates it decreased rss, but the page was shared. * * NOTE! If it sleeps, it *must* return 1 to make sure we * don't continue with the swap-out. Otherwise we may be * using a process that no longer actually exists (it might * have died while we slept). */ static inline int try_to_swap_out(struct task_struct * tsk, struct vm_area_struct* vma, unsigned long address, pte_t * page_table, int dma, int wait, int can_do_io) { pte_t pte; unsigned long entry; unsigned long page; struct page * page_map; pte = *page_table; if (!pte_present(pte)) return 0; page = pte_page(pte); if (MAP_NR(page) >= MAP_NR(high_memory)) return 0; page_map = mem_map + MAP_NR(page); if (PageReserved(page_map) || PageLocked(page_map) || (dma && !PageDMA(page_map))) return 0; /* Deal with page aging. Pages age from being unused; they * rejuvenate on being accessed. Only swap old pages (age==0 * is oldest). */ if ((pte_dirty(pte) && delete_from_swap_cache(MAP_NR(page))) || pte_young(pte)) { set_pte(page_table, pte_mkold(pte)); touch_page(page_map); return 0; } age_page(page_map); if (page_map->age) return 0; if (pte_dirty(pte)) { if(!can_do_io) return 0; if (vma->vm_ops && vma->vm_ops->swapout) { pid_t pid = tsk->pid; vma->vm_mm->rss--; if (vma->vm_ops->swapout(vma, address - vma->vm_start + vma->vm_offset, page_table)) kill_proc(pid, SIGBUS, 1); } else { if (!(entry = get_swap_page())) return 0; vma->vm_mm->rss--; flush_cache_page(vma, address); set_pte(page_table, __pte(entry)); flush_tlb_page(vma, address); tsk->nswap++; rw_swap_page(WRITE, entry, (char *) page, wait); } free_page(page); return 1; /* we slept: the process may not exist any more */ } if ((entry = find_in_swap_cache(MAP_NR(page)))) { if (page_map->count != 1) { set_pte(page_table, pte_mkdirty(pte)); printk("Aiee.. duplicated cached swap-cache entry\n"); return 0; } vma->vm_mm->rss--; flush_cache_page(vma, address); set_pte(page_table, __pte(entry)); flush_tlb_page(vma, address); free_page(page); return 1; } vma->vm_mm->rss--; flush_cache_page(vma, address); pte_clear(page_table); flush_tlb_page(vma, address); entry = page_unuse(page); free_page(page); return entry; } /* * A new implementation of swap_out(). We do not swap complete processes, * but only a small number of blocks, before we continue with the next * process. The number of blocks actually swapped is determined on the * number of page faults, that this process actually had in the last time, * so we won't swap heavily used processes all the time ... * * Note: the priority argument is a hint on much CPU to waste with the * swap block search, not a hint, of how much blocks to swap with * each process. * * (C) 1993 Kai Petzke, wpp@marie.physik.tu-berlin.de */ static inline int swap_out_pmd(struct task_struct * tsk, struct vm_area_struct * vma, pmd_t *dir, unsigned long address, unsigned long end, int dma, int wait, int can_do_io) { pte_t * pte; unsigned long pmd_end; if (pmd_none(*dir)) return 0; if (pmd_bad(*dir)) { printk("swap_out_pmd: bad pmd (%08lx)\n", pmd_val(*dir)); pmd_clear(dir); return 0; } pte = pte_offset(dir, address); pmd_end = (address + PMD_SIZE) & PMD_MASK; if (end > pmd_end) end = pmd_end; do { int result; tsk->swap_address = address + PAGE_SIZE; result = try_to_swap_out(tsk, vma, address, pte, dma, wait, can_do_io); if (result) return result; address += PAGE_SIZE; pte++; } while (address < end); return 0; } static inline int swap_out_pgd(struct task_struct * tsk, struct vm_area_struct * vma, pgd_t *dir, unsigned long address, unsigned long end, int dma, int wait, int can_do_io) { pmd_t * pmd; unsigned long pgd_end; if (pgd_none(*dir)) return 0; if (pgd_bad(*dir)) { printk("swap_out_pgd: bad pgd (%08lx)\n", pgd_val(*dir)); pgd_clear(dir); return 0; } pmd = pmd_offset(dir, address); pgd_end = (address + PGDIR_SIZE) & PGDIR_MASK; if (end > pgd_end) end = pgd_end; do { int result = swap_out_pmd(tsk, vma, pmd, address, end, dma, wait, can_do_io); if (result) return result; address = (address + PMD_SIZE) & PMD_MASK; pmd++; } while (address < end); return 0; } static int swap_out_vma(struct task_struct * tsk, struct vm_area_struct * vma, pgd_t *pgdir, unsigned long start, int dma, int wait, int can_do_io) { unsigned long end; /* Don't swap out areas like shared memory which have their own separate swapping mechanism or areas which are locked down */ if (vma->vm_flags & (VM_SHM | VM_LOCKED)) return 0; end = vma->vm_end; while (start < end) { int result = swap_out_pgd(tsk, vma, pgdir, start, end, dma, wait, can_do_io); if (result) return result; start = (start + PGDIR_SIZE) & PGDIR_MASK; pgdir++; } return 0; } static int swap_out_process(struct task_struct * p, int dma, int wait, int can_do_io) { unsigned long address; struct vm_area_struct* vma; /* * Go through process' page directory. */ address = p->swap_address; /* * Find the proper vm-area */ vma = find_vma(p->mm, address); if (!vma) { p->swap_address = 0; return 0; } if (address < vma->vm_start) address = vma->vm_start; for (;;) { int result = swap_out_vma(p, vma, pgd_offset(p->mm, address), address, dma, wait, can_do_io); if (result) return result; vma = vma->vm_next; if (!vma) break; address = vma->vm_start; } p->swap_address = 0; return 0; } static int swap_out(unsigned int priority, int dma, int wait, int can_do_io) { static int swap_task; int loop, counter, shfrv; struct task_struct *p; #ifdef MM_DEBUG shfrv = 10; #else /* * Trouble due ageing pages: In some situations it is possible that we cross only tasks * which are swapped out or which have only physical pages with age >= 3. * High values of swap_cnt for memory consuming tasks do aggravate such situations. * * If PAGEOUT_WEIGHT has a value of 8192 a right shift value of 10 leads to * (8 * nr_tasks) >> priority * Together with a high number of tasks, say 100, we have counters (due priority) * 12(6) + 25(5) + 50(4) + 100(3) + 200(2) + 400(1) + 800(0) * and as total result 1587 scans of swap_out() to swap out a task page. * * Just assume 80 tasks are swapped out and the remaining tasks have a swap_cnt value >= 40 * together with pages with age >= 3. Then we need approx 20*40*2 = 1600 scans to get a * free page. * And now assume that the amount of cached pages, buffers, and ipc pages are really low. */ switch (priority) { case 6: case 5: case 4: /* be friendly */ shfrv = 10; break; case 3: case 2: case 1: /* more intensive */ shfrv = 9; break; case 0: default: /* sorry we need a page */ shfrv = 8; break; } /* * kswapd should be more friendly to other processes. */ if (kswapd_awake) shfrv = 10; #endif counter = ((PAGEOUT_WEIGHT * nr_tasks) >> shfrv) >> priority; for(; counter >= 0; counter--) { /* * Check that swap_task is suitable for swapping. If not, look for * the next suitable process. */ loop = 0; while(1) { if (swap_task >= NR_TASKS) { swap_task = 1; if (loop) /* all processes are unswappable or already swapped out */ return 0; loop = 1; } p = task[swap_task]; if (p && p->swappable && p->mm->rss) break; swap_task++; } /* * Determine the number of pages to swap from this process. */ if (!p->swap_cnt) { /* * Normalise the number of pages swapped by * multiplying by (RSS / 1MB) */ p->swap_cnt = AGE_CLUSTER_SIZE(p->mm->rss); } if (!--p->swap_cnt) swap_task++; switch (swap_out_process(p, dma, wait, can_do_io)) { case 0: if (p->state == TASK_STOPPED) /* Stopped task occupy nonused ram */ break; if (p->swap_cnt) swap_task++; break; case 1: return 1; default: break; } } #ifdef MM_DEBUG if (!priority) { printk("swap_out: physical ram %6dkB, min pages %6dkB\n", (int)(high_memory>>10), min_free_pages<<(PAGE_SHIFT-10)); printk("swap_out: free pages %6dkB, async pages %6dkB\n", nr_free_pages<<(PAGE_SHIFT-10), nr_async_pages<<(PAGE_SHIFT-10)); } #endif return 0; } /* * We are much more aggressive about trying to swap out than we used * to be. This works out OK, because we now do proper aging on page * contents. */ int try_to_free_page(int priority, int dma, int wait) { static int state = 0; int i=6; int stop, can_do_io; /* we don't try as hard if we're not waiting.. */ stop = 3; can_do_io = 1; if (wait) stop = 0; if (priority == GFP_IO) can_do_io = 0; switch (state) { do { case 0: if (shrink_mmap(i, dma, 1)) return 1; state = 1; case 1: if (can_do_io && shm_swap(i, dma)) return 1; state = 2; default: if (swap_out(i, dma, wait, can_do_io)) return 1; state = 0; i--; } while ((i - stop) >= 0); } return 0; } /* * Before we start the kernel thread, print out the * kswapd initialization message (otherwise the init message * may be printed in the middle of another driver's init * message). It looks very bad when that happens. */ void kswapd_setup(void) { int i; char *revision="$Revision: 1.1 $", *s, *e; if ((s = strchr(revision, ':')) && (e = strchr(s, '$'))) s++, i = e - s; else s = revision, i = -1; printk ("Starting kswapd v%.*s\n", i, s); } /* * The background pageout daemon. * Started as a kernel thread from the init process. */ int kswapd(void *unused) { int i, reserved_pages; current->session = 1; current->pgrp = 1; sprintf(current->comm, "kswapd"); current->blocked = ~0UL; /* * As a kernel thread we want to tamper with system buffers * and other internals and thus be subject to the SMP locking * rules. (On a uniprocessor box this does nothing). */ #ifdef __SMP__ lock_kernel(); syscall_count++; #endif /* Give kswapd a realtime priority. */ current->policy = SCHED_FIFO; current->priority = 32; /* Fixme --- we need to standardise our namings for POSIX.4 realtime scheduling priorities. */ init_swap_timer(); while (1) { /* low on memory, we need to start swapping soon */ next_swap_jiffies = jiffies + (last_wakeup_low ? swapout_interval >> 1 : swapout_interval); kswapd_awake = 0; current->signal = 0; run_task_queue(&tq_disk); interruptible_sleep_on(&kswapd_wait); kswapd_awake = 1; swapstats.wakeups++; /* Protect our reserved pages: */ i = 0; reserved_pages = min_free_pages; if (min_free_pages >= 48) reserved_pages -= (12 + (reserved_pages>>3)); if (nr_free_pages <= reserved_pages) i = (1+reserved_pages) - nr_free_pages; /* Do the background pageout: */ for (i += kswapd_ctl.maxpages; i > 0; i--) try_to_free_page(GFP_KERNEL, 0, (nr_free_pages <= min_free_pages)); } } /* * The swap_tick function gets called on every clock tick. */ void swap_tick(void) { int want_wakeup = 0; if ((nr_free_pages + nr_async_pages) < free_pages_low) { if (last_wakeup_low) want_wakeup = (jiffies >= next_swap_jiffies); else last_wakeup_low = want_wakeup = 1; } else if (((nr_free_pages + nr_async_pages) < free_pages_high) && (jiffies >= next_swap_jiffies)) { last_wakeup_low = 0; want_wakeup = 1; } if (want_wakeup) { if (!kswapd_awake && kswapd_ctl.maxpages > 0) { wake_up(&kswapd_wait); need_resched = 1; } } timer_active |= (1<<SWAP_TIMER); } /* * Initialise the swap timer */ void init_swap_timer(void) { timer_table[SWAP_TIMER].expires = 0; timer_table[SWAP_TIMER].fn = swap_tick; timer_active |= (1<<SWAP_TIMER); }
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