patch-1.3.57 linux/mm/vmscan.c

• Lines: 428
• Date: Fri Jan 12 07:07:11 1996
• Orig file: v1.3.56/linux/mm/vmscan.c
• Orig date: Thu Jan 1 02:00:00 1970

diff -u --recursive --new-file v1.3.56/linux/mm/vmscan.c linux/mm/vmscan.c
@@ -0,0 +1,427 @@
+/*
+ *  linux/mm/vmscan.c
+ *
+ *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ *
+ *  Swap reorganised 29.12.95, 
+ */
+
+#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/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>
+
+/* 
+ * When are we next due for a page scan? 
+ */
+static int next_swap_jiffies = 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, unsigned long limit)
+{
+	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;
+	if (page >= limit)
+		return 0;
+
+	page_map = mem_map + MAP_NR(page);
+	if (page_map->reserved)
+		return 0;
+	/* Deal with page aging.  Pages age from being unused; they
+	 * rejuvinate on being accessed.  Only swap old pages (age==0
+	 * is oldest). */
+	if ((pte_dirty(pte) && delete_from_swap_cache(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 (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 (page_map->count != 1)
+				return 0;
+			if (!(entry = get_swap_page()))
+				return 0;
+			vma->vm_mm->rss--;
+			set_pte(page_table, __pte(entry));
+			invalidate_page(vma, address);
+			tsk->nswap++;
+			write_swap_page(entry, (char *) page);
+		}
+		free_page(page);
+		return 1;	/* we slept: the process may not exist any more */
+	}
+        if ((entry = find_in_swap_cache(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--;
+		set_pte(page_table, __pte(entry));
+		invalidate_page(vma, address);
+		free_page(page);
+		return 1;
+	} 
+	vma->vm_mm->rss--;
+	pte_clear(page_table);
+	invalidate_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, unsigned long limit)
+{
+	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, limit);
+		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, unsigned long limit)
+{
+	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, limit);
+		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, unsigned long limit)
+{
+	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, limit);
+		if (result)
+			return result;
+		start = (start + PGDIR_SIZE) & PGDIR_MASK;
+		pgdir++;
+	}
+	return 0;
+}
+
+static int swap_out_process(struct task_struct * p, unsigned long limit)
+{
+	unsigned long address;
+	struct vm_area_struct* vma;
+
+	/*
+	 * Go through process' page directory.
+	 */
+	address = p->swap_address;
+	p->swap_address = 0;
+
+	/*
+	 * Find the proper vm-area
+	 */
+	vma = find_vma(p, address);
+	if (!vma)
+		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, limit);
+		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, unsigned long limit)
+{
+	static int swap_task;
+	int loop, counter;
+	struct task_struct *p;
+
+	counter = ((PAGEOUT_WEIGHT * nr_tasks) >> 10) >> 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, limit)) {
+			case 0:
+				if (p->swap_cnt)
+					swap_task++;
+				break;
+			case 1:
+				return 1;
+			default:
+				break;
+		}
+	}
+	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, unsigned long limit)
+{
+	static int state = 0;
+	int i=6;
+
+	switch (state) {
+		do {
+		case 0:
+			if (shrink_mmap(i, limit))
+				return 1;
+			state = 1;
+		case 1:
+			if (shm_swap(i, limit))
+				return 1;
+			state = 2;
+		default:
+			if (swap_out(i, limit))
+				return 1;
+			state = 0;
+		} while(i--);
+	}
+	return 0;
+}
+
+
+/*
+ * The background pageout daemon.
+ * Started as a kernel thread from the init process.
+ */
+int kswapd(void *unused)
+{
+	int i;
+	
+	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.  */
+
+	printk ("Started kswapd v$Revision: 1.1.2.3 $\n");
+	init_swap_timer();
+	
+	while (1) {
+		kswapd_awake = 0;
+		current->signal = 0;
+		interruptible_sleep_on(&kswapd_wait);
+		kswapd_awake = 1;
+		
+		/* Do the background pageout: */
+		for (i=0; i < kswapd_ctl.maxpages; i++)
+			try_to_free_page(GFP_KERNEL, ~0UL);
+	}
+}
+
+/* 
+ * The swap_tick function gets called on every clock tick.
+ */
+
+void swap_tick(void)
+{
+	if (nr_free_pages < free_pages_low ||
+	    (nr_free_pages < free_pages_high && 
+	     jiffies >= next_swap_jiffies)) {
+		if (!kswapd_awake && kswapd_ctl.maxpages > 0) {
+			wake_up(&kswapd_wait);
+			need_resched = 1;
+			kswapd_awake = 1;
+		}
+		next_swap_jiffies = jiffies + swapout_interval;
+	}
+	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);
+}