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    SubjectRe: [RFC 1/8] Only isolate page we can handle
    On Wed, Apr 27, 2011 at 01:25:18AM +0900, Minchan Kim wrote:
    > There are some places to isolate lru page and I believe
    > users of isolate_lru_page will be growing.
    > The purpose of them is each different so part of isolated pages
    > should put back to LRU, again.
    >
    > The problem is when we put back the page into LRU,
    > we lose LRU ordering and the page is inserted at head of LRU list.
    > It makes unnecessary LRU churning so that vm can evict working set pages
    > rather than idle pages.
    >
    > This patch adds new filter mask when we isolate page in LRU.
    > So, we don't isolate pages if we can't handle it.
    > It could reduce LRU churning.
    >
    > This patch shouldn't change old behavior.
    > It's just used by next patches.
    >
    > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    > Cc: Mel Gorman <mgorman@suse.de>
    > Cc: Rik van Riel <riel@redhat.com>
    > Cc: Andrea Arcangeli <aarcange@redhat.com>
    > Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
    > ---
    > include/linux/swap.h | 3 ++-
    > mm/compaction.c | 2 +-
    > mm/memcontrol.c | 2 +-
    > mm/vmscan.c | 26 ++++++++++++++++++++------
    > 4 files changed, 24 insertions(+), 9 deletions(-)
    >
    > diff --git a/include/linux/swap.h b/include/linux/swap.h
    > index 384eb5f..baef4ad 100644
    > --- a/include/linux/swap.h
    > +++ b/include/linux/swap.h
    > @@ -259,7 +259,8 @@ extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
    > unsigned int swappiness,
    > struct zone *zone,
    > unsigned long *nr_scanned);
    > -extern int __isolate_lru_page(struct page *page, int mode, int file);
    > +extern int __isolate_lru_page(struct page *page, int mode, int file,
    > + int not_dirty, int not_mapped);

    bool? If you use bitmask later, it's not important though.

    > extern unsigned long shrink_all_memory(unsigned long nr_pages);
    > extern int vm_swappiness;
    > extern int remove_mapping(struct address_space *mapping, struct page *page);
    > diff --git a/mm/compaction.c b/mm/compaction.c
    > index 021a296..dea32e3 100644
    > --- a/mm/compaction.c
    > +++ b/mm/compaction.c
    > @@ -335,7 +335,7 @@ static unsigned long isolate_migratepages(struct zone *zone,
    > }
    >
    > /* Try isolate the page */
    > - if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)
    > + if (__isolate_lru_page(page, ISOLATE_BOTH, 0, 0, 0) != 0)
    > continue;
    >
    > VM_BUG_ON(PageTransCompound(page));
    > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    > index c2776f1..471e7fd 100644
    > --- a/mm/memcontrol.c
    > +++ b/mm/memcontrol.c
    > @@ -1193,7 +1193,7 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
    > continue;
    >
    > scan++;
    > - ret = __isolate_lru_page(page, mode, file);
    > + ret = __isolate_lru_page(page, mode, file, 0, 0);
    > switch (ret) {
    > case 0:
    > list_move(&page->lru, dst);
    > diff --git a/mm/vmscan.c b/mm/vmscan.c
    > index b3a569f..71d2da9 100644
    > --- a/mm/vmscan.c
    > +++ b/mm/vmscan.c
    > @@ -954,10 +954,13 @@ keep_lumpy:
    > *
    > * page: page to consider
    > * mode: one of the LRU isolation modes defined above
    > - *
    > + * file: page be on a file LRU
    > + * not_dirty: page should be not dirty or not writeback
    > + * not_mapped: page should be not mapped
    > * returns 0 on success, -ve errno on failure.
    > */
    > -int __isolate_lru_page(struct page *page, int mode, int file)
    > +int __isolate_lru_page(struct page *page, int mode, int file,
    > + int not_dirty, int not_mapped)
    > {
    > int ret = -EINVAL;
    >
    > @@ -976,6 +979,12 @@ int __isolate_lru_page(struct page *page, int mode, int file)
    > if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
    > return ret;
    >
    > + if (not_dirty)
    > + if (PageDirty(page) || PageWriteback(page))
    > + return ret;
    > + if (not_mapped)
    > + if (page_mapped(page))
    > + return ret;
    > /*
    > * When this function is being called for lumpy reclaim, we
    > * initially look into all LRU pages, active, inactive and
    > @@ -1016,12 +1025,15 @@ int __isolate_lru_page(struct page *page, int mode, int file)
    > * @order: The caller's attempted allocation order
    > * @mode: One of the LRU isolation modes
    > * @file: True [1] if isolating file [!anon] pages
    > + * @not_dirty: True [1] if isolating file [!dirty] pages
    > + * @not_mapped: True [1] if isolating file [!mapped] pages
    > *
    > * returns how many pages were moved onto *@dst.
    > */
    > static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
    > struct list_head *src, struct list_head *dst,
    > - unsigned long *scanned, int order, int mode, int file)
    > + unsigned long *scanned, int order, int mode, int file,
    > + int not_dirty, int not_mapped)
    > {
    > unsigned long nr_taken = 0;
    > unsigned long nr_lumpy_taken = 0;
    > @@ -1041,7 +1053,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
    >
    > VM_BUG_ON(!PageLRU(page));
    >
    > - switch (__isolate_lru_page(page, mode, file)) {
    > + switch (__isolate_lru_page(page, mode, file,
    > + not_dirty, not_mapped)) {
    > case 0:
    > list_move(&page->lru, dst);
    > mem_cgroup_del_lru(page);
    > @@ -1100,7 +1113,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
    > !PageSwapCache(cursor_page))
    > break;
    >
    > - if (__isolate_lru_page(cursor_page, mode, file) == 0) {
    > + if (__isolate_lru_page(cursor_page, mode, file,
    > + not_dirty, not_mapped) == 0) {
    > list_move(&cursor_page->lru, dst);
    > mem_cgroup_del_lru(cursor_page);
    > nr_taken += hpage_nr_pages(page);
    > @@ -1143,7 +1157,7 @@ static unsigned long isolate_pages_global(unsigned long nr,
    > if (file)
    > lru += LRU_FILE;
    > return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
    > - mode, file);
    > + mode, file, 0, 0);
    > }
    >
    > /*
    > --
    > 1.7.1
    >

    --
    Mel Gorman
    SUSE Labs


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