lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

[PATCH] page migration reorg

Browse Source 
Centralize the page migration functions in anticipation of additional
tinkering.  Creates a new file mm/migrate.c

1. Extract buffer_migrate_page() from fs/buffer.c

2. Extract central migration code from vmscan.c

3. Extract some components from mempolicy.c

4. Export pageout() and remove_from_swap() from vmscan.c

5. Make it possible to configure NUMA systems without page migration
   and non-NUMA systems with page migration.

I had to so some #ifdeffing in mempolicy.c that may need a cleanup.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Christoph Lameter
2006-03-22 00:09:12 -08:00
committed by Linus Torvalds
parent 442295c94b
commit b20a35035f
10 changed files with 741 additions and 660 deletions
Download Patch File Download Diff File Expand all files Collapse all files

491
mm/vmscan.c
View File

@@ -42,18 +42,6 @@
#include "internal.h"
/* possible outcome of pageout() */
typedef enum {
/* failed to write page out, page is locked */
PAGE_KEEP,
/* move page to the active list, page is locked */
PAGE_ACTIVATE,
/* page has been sent to the disk successfully, page is unlocked */
PAGE_SUCCESS,
/* page is clean and locked */
PAGE_CLEAN,
} pageout_t;
struct scan_control {
/* Incremented by the number of inactive pages that were scanned */
unsigned long nr_scanned;
@@ -304,7 +292,7 @@ static void handle_write_error(struct address_space *mapping,
* pageout is called by shrink_page_list() for each dirty page.
* Calls ->writepage().
*/
static pageout_t pageout(struct page *page, struct address_space *mapping)
pageout_t pageout(struct page *page, struct address_space *mapping)
{
/*
* If the page is dirty, only perform writeback if that write
@@ -372,7 +360,7 @@ static pageout_t pageout(struct page *page, struct address_space *mapping)
return PAGE_CLEAN;
}
static int remove_mapping(struct address_space *mapping, struct page *page)
int remove_mapping(struct address_space *mapping, struct page *page)
{
if (!mapping)
return 0; /* truncate got there first */
@@ -570,481 +558,6 @@ keep:
return nr_reclaimed;
}
#ifdef CONFIG_MIGRATION
static inline void move_to_lru(struct page *page)
{
list_del(&page->lru);
if (PageActive(page)) {
/*
* lru_cache_add_active checks that
* the PG_active bit is off.
*/
ClearPageActive(page);
lru_cache_add_active(page);
} else {
lru_cache_add(page);
}
put_page(page);
}
/*
* Add isolated pages on the list back to the LRU.
*
* returns the number of pages put back.
*/
unsigned long putback_lru_pages(struct list_head *l)
{
struct page *page;
struct page *page2;
unsigned long count = 0;
list_for_each_entry_safe(page, page2, l, lru) {
move_to_lru(page);
count++;
}
return count;
}
/*
* Non migratable page
*/
int fail_migrate_page(struct page *newpage, struct page *page)
{
return -EIO;
}
EXPORT_SYMBOL(fail_migrate_page);
/*
* swapout a single page
* page is locked upon entry, unlocked on exit
*/
static int swap_page(struct page *page)
{
struct address_space *mapping = page_mapping(page);
if (page_mapped(page) && mapping)
if (try_to_unmap(page, 1) != SWAP_SUCCESS)
goto unlock_retry;
if (PageDirty(page)) {
/* Page is dirty, try to write it out here */
switch(pageout(page, mapping)) {
case PAGE_KEEP:
case PAGE_ACTIVATE:
goto unlock_retry;
case PAGE_SUCCESS:
goto retry;
case PAGE_CLEAN:
; /* try to free the page below */
}
}
if (PagePrivate(page)) {
if (!try_to_release_page(page, GFP_KERNEL) ||
(!mapping && page_count(page) == 1))
goto unlock_retry;
}
if (remove_mapping(mapping, page)) {
/* Success */
unlock_page(page);
return 0;
}
unlock_retry:
unlock_page(page);
retry:
return -EAGAIN;
}
EXPORT_SYMBOL(swap_page);
/*
* Page migration was first developed in the context of the memory hotplug
* project. The main authors of the migration code are:
*
* IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
* Hirokazu Takahashi <taka@valinux.co.jp>
* Dave Hansen <haveblue@us.ibm.com>
* Christoph Lameter <clameter@sgi.com>
*/
/*
* Remove references for a page and establish the new page with the correct
* basic settings to be able to stop accesses to the page.
*/
int migrate_page_remove_references(struct page *newpage,
struct page *page, int nr_refs)
{
struct address_space *mapping = page_mapping(page);
struct page **radix_pointer;
/*
* Avoid doing any of the following work if the page count
* indicates that the page is in use or truncate has removed
* the page.
*/
if (!mapping || page_mapcount(page) + nr_refs != page_count(page))
return -EAGAIN;
/*
* Establish swap ptes for anonymous pages or destroy pte
* maps for files.
*
* In order to reestablish file backed mappings the fault handlers
* will take the radix tree_lock which may then be used to stop
* processses from accessing this page until the new page is ready.
*
* A process accessing via a swap pte (an anonymous page) will take a
* page_lock on the old page which will block the process until the
* migration attempt is complete. At that time the PageSwapCache bit
* will be examined. If the page was migrated then the PageSwapCache
* bit will be clear and the operation to retrieve the page will be
* retried which will find the new page in the radix tree. Then a new
* direct mapping may be generated based on the radix tree contents.
*
* If the page was not migrated then the PageSwapCache bit
* is still set and the operation may continue.
*/
if (try_to_unmap(page, 1) == SWAP_FAIL)
/* A vma has VM_LOCKED set -> Permanent failure */
return -EPERM;
/*
* Give up if we were unable to remove all mappings.
*/
if (page_mapcount(page))
return -EAGAIN;
write_lock_irq(&mapping->tree_lock);
radix_pointer = (struct page **)radix_tree_lookup_slot(
&mapping->page_tree,
page_index(page));
if (!page_mapping(page) || page_count(page) != nr_refs ||
*radix_pointer != page) {
write_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
/*
* Now we know that no one else is looking at the page.
*
* Certain minimal information about a page must be available
* in order for other subsystems to properly handle the page if they
* find it through the radix tree update before we are finished
* copying the page.
*/
get_page(newpage);
newpage->index = page->index;
newpage->mapping = page->mapping;
if (PageSwapCache(page)) {
SetPageSwapCache(newpage);
set_page_private(newpage, page_private(page));
}
*radix_pointer = newpage;
__put_page(page);
write_unlock_irq(&mapping->tree_lock);
return 0;
}
EXPORT_SYMBOL(migrate_page_remove_references);
/*
* Copy the page to its new location
*/
void migrate_page_copy(struct page *newpage, struct page *page)
{
copy_highpage(newpage, page);
if (PageError(page))
SetPageError(newpage);
if (PageReferenced(page))
SetPageReferenced(newpage);
if (PageUptodate(page))
SetPageUptodate(newpage);
if (PageActive(page))
SetPageActive(newpage);
if (PageChecked(page))
SetPageChecked(newpage);
if (PageMappedToDisk(page))
SetPageMappedToDisk(newpage);
if (PageDirty(page)) {
clear_page_dirty_for_io(page);
set_page_dirty(newpage);
}
ClearPageSwapCache(page);
ClearPageActive(page);
ClearPagePrivate(page);
set_page_private(page, 0);
page->mapping = NULL;
/*
* If any waiters have accumulated on the new page then
* wake them up.
*/
if (PageWriteback(newpage))
end_page_writeback(newpage);
}
EXPORT_SYMBOL(migrate_page_copy);
/*
* Common logic to directly migrate a single page suitable for
* pages that do not use PagePrivate.
*
* Pages are locked upon entry and exit.
*/
int migrate_page(struct page *newpage, struct page *page)
{
int rc;
BUG_ON(PageWriteback(page)); /* Writeback must be complete */
rc = migrate_page_remove_references(newpage, page, 2);
if (rc)
return rc;
migrate_page_copy(newpage, page);
/*
* Remove auxiliary swap entries and replace
* them with real ptes.
*
* Note that a real pte entry will allow processes that are not
* waiting on the page lock to use the new page via the page tables
* before the new page is unlocked.
*/
remove_from_swap(newpage);
return 0;
}
EXPORT_SYMBOL(migrate_page);
/*
* migrate_pages
*
* Two lists are passed to this function. The first list
* contains the pages isolated from the LRU to be migrated.
* The second list contains new pages that the pages isolated
* can be moved to. If the second list is NULL then all
* pages are swapped out.
*
* The function returns after 10 attempts or if no pages
* are movable anymore because to has become empty
* or no retryable pages exist anymore.
*
* Return: Number of pages not migrated when "to" ran empty.
*/
unsigned long migrate_pages(struct list_head *from, struct list_head *to,
struct list_head *moved, struct list_head *failed)
{
unsigned long retry;
unsigned long nr_failed = 0;
int pass = 0;
struct page *page;
struct page *page2;
int swapwrite = current->flags & PF_SWAPWRITE;
int rc;
if (!swapwrite)
current->flags |= PF_SWAPWRITE;
redo:
retry = 0;
list_for_each_entry_safe(page, page2, from, lru) {
struct page *newpage = NULL;
struct address_space *mapping;
cond_resched();
rc = 0;
if (page_count(page) == 1)
/* page was freed from under us. So we are done. */
goto next;
if (to && list_empty(to))
break;
/*
* Skip locked pages during the first two passes to give the
* functions holding the lock time to release the page. Later we
* use lock_page() to have a higher chance of acquiring the
* lock.
*/
rc = -EAGAIN;
if (pass > 2)
lock_page(page);
else
if (TestSetPageLocked(page))
goto next;
/*
* Only wait on writeback if we have already done a pass where
* we we may have triggered writeouts for lots of pages.
*/
if (pass > 0) {
wait_on_page_writeback(page);
} else {
if (PageWriteback(page))
goto unlock_page;
}
/*
* Anonymous pages must have swap cache references otherwise
* the information contained in the page maps cannot be
* preserved.
*/
if (PageAnon(page) && !PageSwapCache(page)) {
if (!add_to_swap(page, GFP_KERNEL)) {
rc = -ENOMEM;
goto unlock_page;
}
}
if (!to) {
rc = swap_page(page);
goto next;
}
newpage = lru_to_page(to);
lock_page(newpage);
/*
* Pages are properly locked and writeback is complete.
* Try to migrate the page.
*/
mapping = page_mapping(page);
if (!mapping)
goto unlock_both;
if (mapping->a_ops->migratepage) {
/*
* Most pages have a mapping and most filesystems
* should provide a migration function. Anonymous
* pages are part of swap space which also has its
* own migration function. This is the most common
* path for page migration.
*/
rc = mapping->a_ops->migratepage(newpage, page);
goto unlock_both;
}
/*
* Default handling if a filesystem does not provide
* a migration function. We can only migrate clean
* pages so try to write out any dirty pages first.
*/
if (PageDirty(page)) {
switch (pageout(page, mapping)) {
case PAGE_KEEP:
case PAGE_ACTIVATE:
goto unlock_both;
case PAGE_SUCCESS:
unlock_page(newpage);
goto next;
case PAGE_CLEAN:
; /* try to migrate the page below */
}
}
/*
* Buffers are managed in a filesystem specific way.
* We must have no buffers or drop them.
*/
if (!page_has_buffers(page) ||
try_to_release_page(page, GFP_KERNEL)) {
rc = migrate_page(newpage, page);
goto unlock_both;
}
/*
* On early passes with mapped pages simply
* retry. There may be a lock held for some
* buffers that may go away. Later
* swap them out.
*/
if (pass > 4) {
/*
* Persistently unable to drop buffers..... As a
* measure of last resort we fall back to
* swap_page().
*/
unlock_page(newpage);
newpage = NULL;
rc = swap_page(page);
goto next;
}
unlock_both:
unlock_page(newpage);
unlock_page:
unlock_page(page);
next:
if (rc == -EAGAIN) {
retry++;
} else if (rc) {
/* Permanent failure */
list_move(&page->lru, failed);
nr_failed++;
} else {
if (newpage) {
/* Successful migration. Return page to LRU */
move_to_lru(newpage);
}
list_move(&page->lru, moved);
}
}
if (retry && pass++ < 10)
goto redo;
if (!swapwrite)
current->flags &= ~PF_SWAPWRITE;
return nr_failed + retry;
}
/*
* Isolate one page from the LRU lists and put it on the
* indicated list with elevated refcount.
*
* Result:
* 0 = page not on LRU list
* 1 = page removed from LRU list and added to the specified list.
*/
int isolate_lru_page(struct page *page)
{
int ret = 0;
if (PageLRU(page)) {
struct zone *zone = page_zone(page);
spin_lock_irq(&zone->lru_lock);
if (PageLRU(page)) {
ret = 1;
get_page(page);
ClearPageLRU(page);
if (PageActive(page))
del_page_from_active_list(zone, page);
else
del_page_from_inactive_list(zone, page);
}
spin_unlock_irq(&zone->lru_lock);
}
return ret;
}
#endif
/*
* zone->lru_lock is heavily contended. Some of the functions that
* shrink the lists perform better by taking out a batch of pages