Define page_file_cache() function to answer the question:
is page backed by a file?
Originally part of Rik van Riel's split-lru patch. Extracted
to make available for other, independent reclaim patches.
Moved inline function to linux/mm_inline.h where it will
be needed by subsequent "split LRU" and "noreclaim" patches.
Unfortunately this needs to use a page flag, since the
PG_swapbacked state needs to be preserved all the way
to the point where the page is last removed from the
LRU. Trying to derive the status from other info in
the page resulted in wrong VM statistics in earlier
split VM patchsets.
Signed-off-by: Rik van Riel <[email protected]>
Signed-off-by: Lee Schermerhorn <[email protected]>
Index: linux-2.6.24-rc6-mm1/include/linux/mm_inline.h
===================================================================
--- linux-2.6.24-rc6-mm1.orig/include/linux/mm_inline.h 2008-01-02 12:37:11.000000000 -0500
+++ linux-2.6.24-rc6-mm1/include/linux/mm_inline.h 2008-01-02 12:37:22.000000000 -0500
@@ -1,3 +1,24 @@
+#ifndef LINUX_MM_INLINE_H
+#define LINUX_MM_INLINE_H
+
+/**
+ * page_file_cache(@page)
+ * Returns !0 if @page is page cache page backed by a regular filesystem,
+ * or 0 if @page is anonymous, tmpfs or otherwise ram or swap backed.
+ *
+ * We would like to get this info without a page flag, but the state
+ * needs to survive until the page is last deleted from the LRU, which
+ * could be as far down as __page_cache_release.
+ */
+static inline int page_file_cache(struct page *page)
+{
+ if (PageSwapBacked(page))
+ return 0;
+
+ /* The page is page cache backed by a normal filesystem. */
+ return 2;
+}
+
static inline void
add_page_to_active_list(struct zone *zone, struct page *page)
{
@@ -38,3 +59,4 @@ del_page_from_lru(struct zone *zone, str
}
}
+#endif
Index: linux-2.6.24-rc6-mm1/mm/shmem.c
===================================================================
--- linux-2.6.24-rc6-mm1.orig/mm/shmem.c 2008-01-02 12:37:11.000000000 -0500
+++ linux-2.6.24-rc6-mm1/mm/shmem.c 2008-01-02 12:37:22.000000000 -0500
@@ -1377,6 +1377,7 @@ repeat:
goto failed;
}
+ SetPageSwapBacked(filepage);
spin_lock(&info->lock);
entry = shmem_swp_alloc(info, idx, sgp);
if (IS_ERR(entry))
Index: linux-2.6.24-rc6-mm1/include/linux/page-flags.h
===================================================================
--- linux-2.6.24-rc6-mm1.orig/include/linux/page-flags.h 2008-01-02 12:37:11.000000000 -0500
+++ linux-2.6.24-rc6-mm1/include/linux/page-flags.h 2008-01-02 12:37:22.000000000 -0500
@@ -89,6 +89,7 @@
#define PG_mappedtodisk 16 /* Has blocks allocated on-disk */
#define PG_reclaim 17 /* To be reclaimed asap */
#define PG_buddy 19 /* Page is free, on buddy lists */
+#define PG_swapbacked 20 /* Page is backed by RAM/swap */
/* PG_readahead is only used for file reads; PG_reclaim is only for writes */
#define PG_readahead PG_reclaim /* Reminder to do async read-ahead */
@@ -216,6 +217,10 @@ static inline void SetPageUptodate(struc
#define ClearPageReclaim(page) clear_bit(PG_reclaim, &(page)->flags)
#define TestClearPageReclaim(page) test_and_clear_bit(PG_reclaim, &(page)->flags)
+#define PageSwapBacked(page) test_bit(PG_swapbacked, &(page)->flags)
+#define SetPageSwapBacked(page) set_bit(PG_swapbacked, &(page)->flags)
+#define __ClearPageSwapBacked(page) __clear_bit(PG_swapbacked, &(page)->flags)
+
#define PageCompound(page) test_bit(PG_compound, &(page)->flags)
#define __SetPageCompound(page) __set_bit(PG_compound, &(page)->flags)
#define __ClearPageCompound(page) __clear_bit(PG_compound, &(page)->flags)
Index: linux-2.6.24-rc6-mm1/mm/memory.c
===================================================================
--- linux-2.6.24-rc6-mm1.orig/mm/memory.c 2008-01-02 12:37:11.000000000 -0500
+++ linux-2.6.24-rc6-mm1/mm/memory.c 2008-01-02 12:37:22.000000000 -0500
@@ -1664,6 +1664,7 @@ gotten:
ptep_clear_flush(vma, address, page_table);
set_pte_at(mm, address, page_table, entry);
update_mmu_cache(vma, address, entry);
+ SetPageSwapBacked(new_page);
lru_cache_add_active(new_page);
page_add_new_anon_rmap(new_page, vma, address);
@@ -2131,6 +2132,7 @@ static int do_anonymous_page(struct mm_s
if (!pte_none(*page_table))
goto release;
inc_mm_counter(mm, anon_rss);
+ SetPageSwapBacked(page);
lru_cache_add_active(page);
page_add_new_anon_rmap(page, vma, address);
set_pte_at(mm, address, page_table, entry);
@@ -2284,6 +2286,7 @@ static int __do_fault(struct mm_struct *
set_pte_at(mm, address, page_table, entry);
if (anon) {
inc_mm_counter(mm, anon_rss);
+ SetPageSwapBacked(page);
lru_cache_add_active(page);
page_add_new_anon_rmap(page, vma, address);
} else {
Index: linux-2.6.24-rc6-mm1/mm/swap_state.c
===================================================================
--- linux-2.6.24-rc6-mm1.orig/mm/swap_state.c 2008-01-02 12:37:11.000000000 -0500
+++ linux-2.6.24-rc6-mm1/mm/swap_state.c 2008-01-02 12:37:22.000000000 -0500
@@ -82,6 +82,7 @@ int add_to_swap_cache(struct page *page,
if (!error) {
page_cache_get(page);
SetPageSwapCache(page);
+ SetPageSwapBacked(page);
set_page_private(page, entry.val);
total_swapcache_pages++;
__inc_zone_page_state(page, NR_FILE_PAGES);
Index: linux-2.6.24-rc6-mm1/mm/migrate.c
===================================================================
--- linux-2.6.24-rc6-mm1.orig/mm/migrate.c 2008-01-02 12:37:14.000000000 -0500
+++ linux-2.6.24-rc6-mm1/mm/migrate.c 2008-01-02 12:37:22.000000000 -0500
@@ -546,6 +546,8 @@ static int move_to_new_page(struct page
/* Prepare mapping for the new page.*/
newpage->index = page->index;
newpage->mapping = page->mapping;
+ if (PageSwapBacked(page))
+ SetPageSwapBacked(newpage);
mapping = page_mapping(page);
if (!mapping)
Index: linux-2.6.24-rc6-mm1/mm/page_alloc.c
===================================================================
--- linux-2.6.24-rc6-mm1.orig/mm/page_alloc.c 2008-01-02 12:37:11.000000000 -0500
+++ linux-2.6.24-rc6-mm1/mm/page_alloc.c 2008-01-02 12:37:22.000000000 -0500
@@ -253,6 +253,7 @@ static void bad_page(struct page *page)
1 << PG_slab |
1 << PG_swapcache |
1 << PG_writeback |
+ 1 << PG_swapbacked |
1 << PG_buddy );
set_page_count(page, 0);
reset_page_mapcount(page);
@@ -485,6 +486,8 @@ static inline int free_pages_check(struc
bad_page(page);
if (PageDirty(page))
__ClearPageDirty(page);
+ if (PageSwapBacked(page))
+ __ClearPageSwapBacked(page);
/*
* For now, we report if PG_reserved was found set, but do not
* clear it, and do not free the page. But we shall soon need
@@ -631,6 +634,7 @@ static int prep_new_page(struct page *pa
1 << PG_swapcache |
1 << PG_writeback |
1 << PG_reserved |
+ 1 << PG_swapbacked |
1 << PG_buddy ))))
bad_page(page);
--
All Rights Reversed
On Tue, 8 Jan 2008, Rik van Riel wrote:
> Define page_file_cache() function to answer the question:
> is page backed by a file?
> +static inline int page_file_cache(struct page *page)
> +{
> + if (PageSwapBacked(page))
> + return 0;
Could we call this PageNotFileBacked or so? PageSwapBacked is true for
pages that are RAM based. Its a bit confusing.
> Index: linux-2.6.24-rc6-mm1/mm/migrate.c
> ===================================================================
> --- linux-2.6.24-rc6-mm1.orig/mm/migrate.c 2008-01-02 12:37:14.000000000 -0500
> +++ linux-2.6.24-rc6-mm1/mm/migrate.c 2008-01-02 12:37:22.000000000 -0500
> @@ -546,6 +546,8 @@ static int move_to_new_page(struct page
> /* Prepare mapping for the new page.*/
> newpage->index = page->index;
> newpage->mapping = page->mapping;
> + if (PageSwapBacked(page))
> + SetPageSwapBacked(newpage);
>
> mapping = page_mapping(page);
> if (!mapping)
That hunk belongs into migrate_page_copy()? Or is there a reason that we
need this flag that early?
On Tue, 8 Jan 2008 14:18:40 -0800 (PST)
Christoph Lameter <[email protected]> wrote:
> On Tue, 8 Jan 2008, Rik van Riel wrote:
>
> > Define page_file_cache() function to answer the question:
> > is page backed by a file?
>
> > +static inline int page_file_cache(struct page *page)
> > +{
> > + if (PageSwapBacked(page))
> > + return 0;
>
> Could we call this PageNotFileBacked or so? PageSwapBacked is true for
> pages that are RAM based. Its a bit confusing.
PageNotFileBacked confuses me a little, since shared memory segments live
in tmpfs and are kinda sorta file backed, but go to swap instead of to a
filesystem when there is memory pressure.
I'm always open to better naming ideas, though.
> > Index: linux-2.6.24-rc6-mm1/mm/migrate.c
> > ===================================================================
> > --- linux-2.6.24-rc6-mm1.orig/mm/migrate.c 2008-01-02 12:37:14.000000000 -0500
> > +++ linux-2.6.24-rc6-mm1/mm/migrate.c 2008-01-02 12:37:22.000000000 -0500
> > @@ -546,6 +546,8 @@ static int move_to_new_page(struct page
> > /* Prepare mapping for the new page.*/
> > newpage->index = page->index;
> > newpage->mapping = page->mapping;
> > + if (PageSwapBacked(page))
> > + SetPageSwapBacked(newpage);
> >
> > mapping = page_mapping(page);
> > if (!mapping)
>
> That hunk belongs into migrate_page_copy()? Or is there a reason that we
> need this flag that early?
We want the page added to the right LRU list. I'll have to re-read the
migration code to make sure whether the above can or cannot be done in
migrate_page_copy() - I agree it would fit in better there.
Thanks for the suggestions.
--
All rights reversed.
On Tue, 8 Jan 2008 17:28:56 -0500
Rik van Riel <[email protected]> wrote:
> On Tue, 8 Jan 2008 14:18:40 -0800 (PST)
> Christoph Lameter <[email protected]> wrote:
>
> > On Tue, 8 Jan 2008, Rik van Riel wrote:
> >
> > > Define page_file_cache() function to answer the question:
> > > is page backed by a file?
> >
> > > +static inline int page_file_cache(struct page *page)
> > > +{
> > > + if (PageSwapBacked(page))
> > > + return 0;
> >
> > Could we call this PageNotFileBacked or so? PageSwapBacked is true for
> > pages that are RAM based. Its a bit confusing.
>
> PageNotFileBacked confuses me a little, since shared memory segments live
> in tmpfs and are kinda sorta file backed, but go to swap instead of to a
> filesystem when there is memory pressure.
>
How about PageIsNotCache() ? :)
When a page is a cache, there is an original data somewhere and can be dropped
out.
Thanks,
-Kame