Re: vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru.patch

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 10 Oct 2008 21:53:59 -0400 Rik van Riel <riel@redhat.com> wrote:

> Andrew Morton wrote:
> 
> > I implemented this as a fix against
> > vmscan-fix-pagecache-reclaim-referenced-bit-check.patch, but that patch
> > says 
> 
> > which isn't true any more.
> 
> > Sorry about this mess.
> 
> I'm not sure what else is still in the -mm tree and what got
> removed, so I'm not sure what the new comment for the patch
> should be.

This is getting terrible.

Unfortunately I'm basically dead int he water over here because Stephen
shot through for a month and all the subsystem trees have gone rampant
all over the place.

Apparently mmotm does kinda-compile and kinda-run, but only by luck.

> Maybe the patch could just be folded into an earlier split
> LRU patch now since there no longer is a special case for
> page cache pages?

Yeah, I can do that.  Fold all these:

vmscan-split-lru-lists-into-anon-file-sets.patch
vmscan-split-lru-lists-into-anon-file-sets-memcg-fix-handling-of-shmem-migrationv2.patch
vmscan-split-lru-lists-into-anon-file-sets-adjust-quicklists-field-of-proc-meminfo.patch
vmscan-split-lru-lists-into-anon-file-sets-adjust-hugepage-related-field-of-proc-meminfo.patch
vmscan-split-lru-lists-into-anon-file-sets-fix-style-issue-of-get_scan_ratio.patch
vmscan-second-chance-replacement-for-anonymous-pages.patch
vmscan-fix-pagecache-reclaim-referenced-bit-check.patch
vmscan-fix-pagecache-reclaim-referenced-bit-check-fix.patch
vmscan-fix-pagecache-reclaim-referenced-bit-check-fix-fix.patch

except vmscan-second-chance-replacement-for-anonymous-pages.patch isn't
appropriate for folding.

If I join

vmscan-fix-pagecache-reclaim-referenced-bit-check.patch
vmscan-fix-pagecache-reclaim-referenced-bit-check-fix.patch
vmscan-fix-pagecache-reclaim-referenced-bit-check-fix-fix.patch

then I get the below.  Can we think of a plausible-sounding changelog for it?

--- a/mm/vmscan.c~vmscan-fix-pagecache-reclaim-referenced-bit-check
+++ a/mm/vmscan.c
@@ -1064,7 +1064,6 @@ static void shrink_active_list(unsigned 
 	int pgdeactivate = 0;
 	unsigned long pgscanned;
 	LIST_HEAD(l_hold);	/* The pages which were snipped off */
-	LIST_HEAD(l_active);
 	LIST_HEAD(l_inactive);
 	struct page *page;
 	struct pagevec pvec;
@@ -1095,6 +1094,11 @@ static void shrink_active_list(unsigned 
 		cond_resched();
 		page = lru_to_page(&l_hold);
 		list_del(&page->lru);
+
+		/* page_referenced clears PageReferenced */
+		if (page_mapping_inuse(page) && page_referenced(page))
+			pgmoved++;
+
 		list_add(&page->lru, &l_inactive);
 	}
 
@@ -1103,13 +1107,20 @@ static void shrink_active_list(unsigned 
 	 * to the inactive list.  This helps balance scan pressure between
 	 * file and anonymous pages in get_scan_ratio.
  	 */
+
+	/*
+	 * Count referenced pages from currently used mappings as
+	 * rotated, even though they are moved to the inactive list.
+	 * This helps balance scan pressure between file and anonymous
+	 * pages in get_scan_ratio.
+	 */
 	zone->recent_rotated[!!file] += pgmoved;
 
 	/*
-	 * Now put the pages back on the appropriate [file or anon] inactive
-	 * and active lists.
+	 * Move the pages to the [file or anon] inactive list.
 	 */
 	pagevec_init(&pvec, 1);
+
 	pgmoved = 0;
 	lru = LRU_BASE + file * LRU_FILE;
 	spin_lock_irq(&zone->lru_lock);
@@ -1142,31 +1153,6 @@ static void shrink_active_list(unsigned 
 		pagevec_strip(&pvec);
 		spin_lock_irq(&zone->lru_lock);
 	}
-
-	pgmoved = 0;
-	lru = LRU_ACTIVE + file * LRU_FILE;
-	while (!list_empty(&l_active)) {
-		page = lru_to_page(&l_active);
-		prefetchw_prev_lru_page(page, &l_active, flags);
-		VM_BUG_ON(PageLRU(page));
-		SetPageLRU(page);
-		VM_BUG_ON(!PageActive(page));
-
-		list_move(&page->lru, &zone->lru[lru].list);
-		mem_cgroup_move_lists(page, true);
-		pgmoved++;
-		if (!pagevec_add(&pvec, page)) {
-			__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
-			pgmoved = 0;
-			spin_unlock_irq(&zone->lru_lock);
-			if (vm_swap_full())
-				pagevec_swap_free(&pvec);
-			__pagevec_release(&pvec);
-			spin_lock_irq(&zone->lru_lock);
-		}
-	}
-	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
-
 	__count_zone_vm_events(PGREFILL, zone, pgscanned);
 	__count_vm_events(PGDEACTIVATE, pgdeactivate);
 	spin_unlock_irq(&zone->lru_lock);
_

> We can throw away the loop that moves pages from l_active to the
> active list, because we no longer do that:

yup.

Latest version:

static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
			struct scan_control *sc, int priority, int file)
{
	unsigned long pgmoved;
	int pgdeactivate = 0;
	unsigned long pgscanned;
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
	LIST_HEAD(l_inactive);
	struct page *page;
	struct pagevec pvec;
	enum lru_list lru;

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
	pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
					ISOLATE_ACTIVE, zone,
					sc->mem_cgroup, 1, file);
	/*
	 * zone->pages_scanned is used for detect zone's oom
	 * mem_cgroup remembers nr_scan by itself.
	 */
	if (scan_global_lru(sc)) {
		zone->pages_scanned += pgscanned;
		zone->recent_scanned[!!file] += pgmoved;
	}

	if (file)
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
	else
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
	spin_unlock_irq(&zone->lru_lock);

	pgmoved = 0;
	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);

		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

		/* page_referenced clears PageReferenced */
		if (page_mapping_inuse(page) && page_referenced(page))
			pgmoved++;

		list_add(&page->lru, &l_inactive);
	}

	/*
	 * Count the referenced pages as rotated, even when they are moved
	 * to the inactive list.  This helps balance scan pressure between
	 * file and anonymous pages in get_scan_ratio.
 	 */

	/*
	 * Count referenced pages from currently used mappings as
	 * rotated, even though they are moved to the inactive list.
	 * This helps balance scan pressure between file and anonymous
	 * pages in get_scan_ratio.
	 */
	zone->recent_rotated[!!file] += pgmoved;

	/*
	 * Move the pages to the [file or anon] inactive list.
	 */
	pagevec_init(&pvec, 1);

	pgmoved = 0;
	lru = LRU_BASE + file * LRU_FILE;
	spin_lock_irq(&zone->lru_lock);
	while (!list_empty(&l_inactive)) {
		page = lru_to_page(&l_inactive);
		prefetchw_prev_lru_page(page, &l_inactive, flags);
		VM_BUG_ON(PageLRU(page));
		SetPageLRU(page);
		VM_BUG_ON(!PageActive(page));
		ClearPageActive(page);

		list_move(&page->lru, &zone->lru[lru].list);
		mem_cgroup_move_lists(page, lru);
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
			__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
			spin_unlock_irq(&zone->lru_lock);
			pgdeactivate += pgmoved;
			pgmoved = 0;
			if (buffer_heads_over_limit)
				pagevec_strip(&pvec);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
	pgdeactivate += pgmoved;
	if (buffer_heads_over_limit) {
		spin_unlock_irq(&zone->lru_lock);
		pagevec_strip(&pvec);
		spin_lock_irq(&zone->lru_lock);
	}
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
	__count_vm_events(PGDEACTIVATE, pgdeactivate);
	spin_unlock_irq(&zone->lru_lock);
	if (vm_swap_full())
		pagevec_swap_free(&pvec);

	pagevec_release(&pvec);
}



ho hum.  I'll do a mmotm right now.

My queue up to and including
mmap-handle-mlocked-pages-during-map-remap-unmap-mlock-update-locked_vm-on-munmap-of-mlocked-region.patch
(against 2.6.27-rc9) is at http://userweb.kernel.org/~akpm/rvr.gz

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