Re: [PATCH] 2/5 VM changes: skip-writepage.patch

From: Andrew Morton (akpm@osdl.org)
Date: Wed Jul 09 2003 - 05:12:42 EST


Nikita Danilov <Nikita@Namesys.COM> wrote:
>
> Don't call ->writepage from VM scanner when page is met for the first time
> during scan.

I don't think we need all the code reorganisation. Something like this:

 include/linux/page-flags.h | 7 +++++++
 mm/page_alloc.c | 1 +
 mm/truncate.c | 2 ++
 mm/vmscan.c | 10 ++++++++--
 5 files changed, 18 insertions(+), 2 deletions(-)

diff -puN include/linux/mm_inline.h~skip-writepage include/linux/mm_inline.h
diff -puN include/linux/page-flags.h~skip-writepage include/linux/page-flags.h
--- 25/include/linux/page-flags.h~skip-writepage 2003-07-09 02:58:48.000000000 -0700
+++ 25-akpm/include/linux/page-flags.h 2003-07-09 02:58:48.000000000 -0700
@@ -75,6 +75,7 @@
 #define PG_mappedtodisk 17 /* Has blocks allocated on-disk */
 #define PG_reclaim 18 /* To be reclaimed asap */
 #define PG_compound 19 /* Part of a compound page */
+#define PG_skipped 20 /* ->writepage() was skipped on this page */
 
 
 /*
@@ -267,6 +268,12 @@ extern void get_full_page_state(struct p
 #define SetPageCompound(page) set_bit(PG_compound, &(page)->flags)
 #define ClearPageCompound(page) clear_bit(PG_compound, &(page)->flags)
 
+#define PageSkipped(page) test_bit(PG_skipped, &(page)->flags)
+#define SetPageSkipped(page) set_bit(PG_skipped, &(page)->flags)
+#define TestSetPageSkipped(page) test_and_set_bit(PG_skipped, &(page)->flags)
+#define ClearPageSkipped(page) clear_bit(PG_skipped, &(page)->flags)
+#define TestClearPageSkipped(page) test_and_clear_bit(PG_skipped, &(page)->flags)
+
 /*
  * The PageSwapCache predicate doesn't use a PG_flag at this time,
  * but it may again do so one day.
diff -puN mm/vmscan.c~skip-writepage mm/vmscan.c
--- 25/mm/vmscan.c~skip-writepage 2003-07-09 02:58:48.000000000 -0700
+++ 25-akpm/mm/vmscan.c 2003-07-09 03:05:43.000000000 -0700
@@ -328,6 +328,8 @@ shrink_list(struct list_head *page_list,
                  * See swapfile.c:page_queue_congested().
                  */
                 if (PageDirty(page)) {
+ if (!TestSetPageSkipped(page))
+ goto keep_locked;
                         if (!is_page_cache_freeable(page))
                                 goto keep_locked;
                         if (!mapping)
@@ -351,6 +353,7 @@ shrink_list(struct list_head *page_list,
                                 list_move(&page->list, &mapping->locked_pages);
                                 spin_unlock(&mapping->page_lock);
 
+ ClearPageSkipped(page);
                                 SetPageReclaim(page);
                                 res = mapping->a_ops->writepage(page, &wbc);
 
@@ -533,10 +536,13 @@ shrink_cache(const int nr_pages, struct
                         if (TestSetPageLRU(page))
                                 BUG();
                         list_del(&page->lru);
- if (PageActive(page))
+ if (PageActive(page)) {
+ if (PageSkipped(page))
+ ClearPageSkipped(page);
                                 add_page_to_active_list(zone, page);
- else
+ } else {
                                 add_page_to_inactive_list(zone, page);
+ }
                         if (!pagevec_add(&pvec, page)) {
                                 spin_unlock_irq(&zone->lru_lock);
                                 __pagevec_release(&pvec);
diff -puN mm/truncate.c~skip-writepage mm/truncate.c
--- 25/mm/truncate.c~skip-writepage 2003-07-09 03:05:53.000000000 -0700
+++ 25-akpm/mm/truncate.c 2003-07-09 03:06:37.000000000 -0700
@@ -53,6 +53,7 @@ truncate_complete_page(struct address_sp
         clear_page_dirty(page);
         ClearPageUptodate(page);
         ClearPageMappedToDisk(page);
+ ClearPageSkipped(page);
         remove_from_page_cache(page);
         page_cache_release(page); /* pagecache ref */
 }
@@ -81,6 +82,7 @@ invalidate_complete_page(struct address_
         __remove_from_page_cache(page);
         spin_unlock(&mapping->page_lock);
         ClearPageUptodate(page);
+ ClearPageSkipped(page);
         page_cache_release(page); /* pagecache ref */
         return 1;
 }
diff -puN mm/page_alloc.c~skip-writepage mm/page_alloc.c
--- 25/mm/page_alloc.c~skip-writepage 2003-07-09 03:06:33.000000000 -0700
+++ 25-akpm/mm/page_alloc.c 2003-07-09 03:06:48.000000000 -0700
@@ -220,6 +220,7 @@ static inline void free_pages_check(cons
                         1 << PG_locked |
                         1 << PG_active |
                         1 << PG_reclaim |
+ 1 << PG_skipped |
                         1 << PG_writeback )))
                 bad_page(function, page);
         if (PageDirty(page))

_

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