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SubjectRe: [PATCH v3 15/21] mm: handle lruvec relocks on lumpy reclaim
On Thu, 23 Feb 2012 17:52:52 +0400
Konstantin Khlebnikov <khlebnikov@openvz.org> wrote:

> Prepare for lock splitting in lumly reclaim logic.
> Now move_active_pages_to_lru() and putback_inactive_pages()
> can put pages into different lruvecs.
>
> * relock book before SetPageLRU()

lruvec ?

> * update reclaim_stat pointer after relocks
> * return currently locked lruvec
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
> ---
> mm/vmscan.c | 45 +++++++++++++++++++++++++++++++++------------
> 1 files changed, 33 insertions(+), 12 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index a3941d1..6eeeb4b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1114,6 +1114,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> unsigned long *nr_scanned, struct scan_control *sc,
> isolate_mode_t mode, int active, int file)
> {
> + struct lruvec *cursor_lruvec = lruvec;
> struct list_head *src;
> unsigned long nr_taken = 0;
> unsigned long nr_lumpy_taken = 0;
> @@ -1197,14 +1198,17 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> !PageSwapCache(cursor_page))
> break;
>
> + /* Switch cursor_lruvec lock for lumpy isolate */
> + if (!__lock_page_lruvec_irq(&cursor_lruvec,
> + cursor_page))
> + continue;
> +
> if (__isolate_lru_page(cursor_page, mode, file) == 0) {
> unsigned int isolated_pages;
> - struct lruvec *cursor_lruvec;
> int cursor_lru = page_lru(cursor_page);
>
> list_move(&cursor_page->lru, dst);
> isolated_pages = hpage_nr_pages(cursor_page);
> - cursor_lruvec = page_lruvec(cursor_page);
> cursor_lruvec->pages_count[cursor_lru] -=
> isolated_pages;
> VM_BUG_ON((long)cursor_lruvec->
> @@ -1235,6 +1239,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> }
> }
>
> + /* Restore original lruvec lock */
> + cursor_lruvec = __relock_page_lruvec(cursor_lruvec, page);
> +
> /* If we break out of the loop above, lumpy reclaim failed */
> if (pfn < end_pfn)
> nr_lumpy_failed++;
> @@ -1325,7 +1332,10 @@ static int too_many_isolated(struct zone *zone, int file,
> return isolated > inactive;
> }
>
> -static noinline_for_stack void
> +/*
> + * Returns currently locked lruvec
> + */
> +static noinline_for_stack struct lruvec *
> putback_inactive_pages(struct lruvec *lruvec,
> struct list_head *page_list)
> {
> @@ -1347,10 +1357,13 @@ putback_inactive_pages(struct lruvec *lruvec,
> lock_lruvec_irq(lruvec);
> continue;
> }
> +
> + lruvec = __relock_page_lruvec(lruvec, page);
> + reclaim_stat = &lruvec->reclaim_stat;
> +
> SetPageLRU(page);
> lru = page_lru(page);
>
> - lruvec = page_lruvec(page);
> add_page_to_lru_list(lruvec, page, lru);
> if (is_active_lru(lru)) {
> int file = is_file_lru(lru);
> @@ -1375,6 +1388,8 @@ putback_inactive_pages(struct lruvec *lruvec,
> * To save our caller's stack, now use input list for pages to free.
> */
> list_splice(&pages_to_free, page_list);
> +
> + return lruvec;
> }
>
> static noinline_for_stack void
> @@ -1544,7 +1559,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
> __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
> __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
>
> - putback_inactive_pages(lruvec, &page_list);
> + lruvec = putback_inactive_pages(lruvec, &page_list);
>
> __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
> __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
> @@ -1603,12 +1618,15 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
> *
> * The downside is that we have to touch page->_count against each page.
> * But we had to alter page->flags anyway.
> + *
> + * Returns currently locked lruvec
> */
>
> -static void move_active_pages_to_lru(struct lruvec *lruvec,
> - struct list_head *list,
> - struct list_head *pages_to_free,
> - enum lru_list lru)
> +static struct lruvec *
> +move_active_pages_to_lru(struct lruvec *lruvec,
> + struct list_head *list,
> + struct list_head *pages_to_free,
> + enum lru_list lru)
> {
> unsigned long pgmoved = 0;
> struct page *page;
> @@ -1630,10 +1648,11 @@ static void move_active_pages_to_lru(struct lruvec *lruvec,
>
> page = lru_to_page(list);
>
> + lruvec = __relock_page_lruvec(lruvec, page);
> +
> VM_BUG_ON(PageLRU(page));
> SetPageLRU(page);
>
> - lruvec = page_lruvec(page);
> list_move(&page->lru, &lruvec->pages_lru[lru]);
> numpages = hpage_nr_pages(page);
> lruvec->pages_count[lru] += numpages;
> @@ -1655,6 +1674,8 @@ static void move_active_pages_to_lru(struct lruvec *lruvec,
> __mod_zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru, pgmoved);
> if (!is_active_lru(lru))
> __count_vm_events(PGDEACTIVATE, pgmoved);
> +
> + return lruvec;
> }
>
> static void shrink_active_list(unsigned long nr_to_scan,
> @@ -1744,9 +1765,9 @@ static void shrink_active_list(unsigned long nr_to_scan,
> */
> reclaim_stat->recent_rotated[file] += nr_rotated;
>
> - move_active_pages_to_lru(lruvec, &l_active, &l_hold,
> + lruvec = move_active_pages_to_lru(lruvec, &l_active, &l_hold,
> LRU_ACTIVE + file * LRU_FILE);
> - move_active_pages_to_lru(lruvec, &l_inactive, &l_hold,
> + lruvec = move_active_pages_to_lru(lruvec, &l_inactive, &l_hold,
> LRU_BASE + file * LRU_FILE);
> __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
> unlock_lruvec_irq(lruvec);
>

Hmm...could you add comments to each function as
"The caller should _lock_ lruvec before calling this functions.
This function returns a lruvec with _locked_. It may be different from passed one.
And The callser should unlock lruvec"


Thanks,
-Kame






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